hen people with diabetes can control their
blood sugar
(glucose), they
are more likely to stay healthy. People with diabetes use two kinds of
management devices: glucose meters and other diabetes management tests.
Glucose meters help people with diabetes check their blood sugar at home,
school, work, and play. Other blood and urine tests reveal trends in diabetes
management and help identify diabetes complications.
Glucose Meters
Other Diabetes Management Tests
Glucose Meters
Self-Monitoring of Blood Glucose
The process of monitoring one's own blood glucose with a glucose meter
is often referred to as self-monitoring of blood glucose or "SMBG."
Portable glucose meters are small battery-operated devices. For a picture
of a portable blood glucose meter, use the following link:
Blood Glucose Meter — Medical Encyclopedia — Illustration
http://www.nlm.nih.gov/medlineplus/ency/imagepage/17152.htm
To test for glucose with a typical glucose meter, place a small sample
of blood on a disposable "test strip" and place the strip in
the meter. The test strips are coated with chemicals (glucose oxidase,
dehydrogenase, or hexokinase) that combine with glucose in blood. The
meter measures how much glucose is present. Meters do this in different
ways. Some measure the amount of electricity that can pass through the
sample. Others measure how much light reflects from it. The meter displays
the glucose level as a number. Several new models can record and store
a number of test results. Some models can connect to personal computers
to store test results or print them out.
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Choosing a Glucose Meter
At least 25 different meters are commercially available.
They differ in several ways including
- Amount of blood needed for each test
- Testing speed
- Overall size
- Ability to store test results in memory
- Cost of the meter
- Cost of the test strips used
To search FDA's 510(k) database for glucose meters available over-the-counter
(without a prescription), use the following link:
FDA
510(k) Database Search (Over-the-Counter Glucose Meters)
Newer meters often have features that make them easier to use than older
models. Some meters allow you to get blood from places other than your
fingertip (Alternative Site Testing). Some new models
have automatic timing, error codes and signals, or barcode readers to
help with calibration. Some meters have a large display screen or spoken
instructions for people with visual impairments.
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Using Your Glucose Meter
Diabetes care should be designed for each individual patient. Some patients
may need to test (monitor) more often than others do. How often you use
your glucose meter should be based on the recommendation of your health
care provider. Self-monitoring of blood glucose (SMBG) is recommended
for all people with diabetes, but especially for those who take insulin.
The role of SMBG has not been defined for people with stable
type 2 diabetes
treated only with diet.
As a general rule, the American Diabetes Association (ADA) recommends
that most patients with
type 1 diabetes
test glucose three or more times
per day. Pregnant women taking insulin for
gestational diabetes
should
test two times per day. ADA does not specify how often people with type
2 diabetes should test their glucose, but testing often helps control.
Often, self-monitoring plans direct you to test your blood sugar before
meals, 2 hours after meals, at bedtime, at 3 a.m., and anytime you experience
signs or symptoms. You should test more often when you change medications,
when you have unusual stress or illness, or in other unusual circumstances.
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Learning to Use Your Glucose Meter
Not all glucose meters work the same way. Since you need to know how
to use your glucose meter and interpret its results, you should get training
from a diabetes educator. The educator should watch you test your glucose
to make sure you can use your meter correctly. This training is better
if it is part of an overall diabetes education program.
For information about diabetes education programs recognized by the American
Diabetes Association, use the following link:
ADA Recognized Education Programs
http://www.diabetes.org/education/edustate2.asp?loc=x
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Instructions for Using Glucose Meters
The following are the general instructions for using a glucose meter:
1. Wash hands with soap and warm water and dry completely or clean the
area with alcohol and dry completely.
2. Prick the fingertip with a lancet.
3. Hold the hand down and hold the finger until a small drop of blood
appears; catch the blood with the test strip.
4. Follow the instructions for inserting the test strip and using the
SMBG meter.
5. Record the test result.
FDA requires that glucose meters and the strips used with them have instructions
for use. You should read carefully the instructions for both the meter
and its test strips. Meter instructions are found in the user manual.
Keep this manual to help you solve any problems that may arise. Many meters
use "error codes" when there is a problem with the meter, the
test strip, or the blood sample on the strip. You will need the manual
to interpret these error codes and fix the problem.
You can get information about your meter and test strips from several
different sources. Your user manual should include a toll free number
in case you have questions or problems. If you have a problem and can't
get a response from this number, contact your healthcare provider or a
local emergency room for advice. Also, the manufacturer of your meter
should have a website. Check this website regularly to see if it lists
any issues with the function of your meter.
New devices are for sale such as laser lancets and meters that can test
blood taken from "alternative sites" of the body other than
fingertips. Since new devices are used in new ways and often have new
use restrictions, you must review the instructions carefully.
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Important Features Of Glucose Meters
There are several features of glucose meters that you need to understand
so you can use your meter and understand its results. These features are
often different for different meters. You should understand the features
of your own meter.
Measurement Range. Most glucose meters are able to read glucose
levels over a broad range of values from as low as 0 to as high as 600
mg/dL. Since the range is different among meters, interpret very high
or low values carefully. Glucose readings are not linear over their
entire range. If you get an extremely high or low reading from your
meter, you should first confirm it with another reading. You should
also consider checking your meter's calibration.
Whole Blood Glucose vs. Plasma Glucose. Glucose levels in plasma
(one of the components of blood) are generally 10-15% higher than glucose
measurements in whole blood (and even more after eating). This is important
because home blood glucose meters measure the glucose in whole blood
while most lab tests measure the glucose in plasma. There are
many meters on the market now that give results as "plasma equivalent".
This allows patients to easily compare their glucose measurements in
a lab test and at home. Remember, this is just the way that the measurement
is presented to you. All portable blood glucose meters measure the amount
of glucose in whole blood. The meters that give "plasma equivalent"
readings have a built in algorithm that translates the whole blood measurement
to make it seem like the result that would be obtained on a plasma sample.
It is important for you and your healthcare provider to know whether
your meter gives its results as "whole blood equivalent" or
"plasma equivalent."
Cleaning. Some meters need regular cleaning to be accurate.
Clean your meter with soap and water, using only a dampened soft cloth
to avoid damage to sensitive parts. Do not use alcohol (unless recommended
in the instructions), cleansers with ammonia, glass cleaners, or abrasive
cleaners. Some meters do not require regular cleaning but contain electronic
alerts indicating when you should clean them. Other meters can be cleaned
only by the manufacturer.
Display Of High And Low Glucose Values. Part of learning how
to operate a meter is understanding what the meter results mean. Be
sure you know how high and low glucose concentrations are displayed
on your meter.
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Factors That Affect Glucose Meter Performance
The accuracy of your test results depends partly on the quality of your
meter and test strips and your training. Other factors can also make a
difference in the accuracy of your results.
Hematocrit. Hematocrit is the amount of red blood cells in the
blood. Patients with higher hematocrit values will usually test lower
for blood glucose than patients with normal hematocrit. Patients with
lower hematocrit values will test higher. If you know that you have
abnormal hematocrit values you should discuss its possible effect on
glucose testing (and
HbA1c
testing) with your health care provider.
Anemia and Sickle Cell Anemia are two conditions that affect hematocrit
values.
Other Substances. Many other substances may interfere with your
testing process. These include uric acid (a natural substance in the
body that can be more concentrated in some people with diabetes), glutathione
(an "anti-oxidant" also called "GSH"), and ascorbic
acid (vitamin C). You should check the package insert for each meter
to find what substances might affect its testing accuracy, and discuss
your concerns with your health care provider.
Altitude, Temperature and Humidity. Altitude, room temperature,
and humidity can cause unpredictable effects on glucose results. Check
the meter and test strip package insert for information on these issues.
Store and handle the meter and test strips according to the instructions.
Third-Party Test Strips. Third-party or "generic glucose
reagent strips" are test strips developed as a less expensive option
than the strips that the manufacturer intended the meter to be used
with. They are typically developed by copying the original strips. Although
these strips may work on the meter listed on the package, they could
look like strips used for other meters. Be sure the test strip you use
is compatible with your glucose meter.
Sometimes manufacturers change their meters and their test strips.
These changes are not always communicated to the third-party strip manufacturers.
This can make third-party strips incompatible with your meter without
your knowledge. Differences can involve the amount, type or concentration
of the chemicals (called "reagents") on the test strip, or
the actual size and shape of the strip itself. Meters are sensitive
to these features of test strips and may not work well or consistently
if they are not correct for a meter. If you are unsure whether or not
a certain test strip will work with you meter, contact the manufacturer
of your glucose meter.
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Making Sure Your Meter Works Properly
You should perform quality-control checks to make sure that your home
glucose testing is accurate and reliable. Several things can reduce the
accuracy of your meter reading even if it appears to still work. For instance,
the meter may have been dropped or its electrical components may have
worn out. Humidity or heat may damage test strips. It is even possible
that your testing technique may have changed slightly. Quality control
checks should be done on a regular basis according to the meter manufacturer's
instructions. There are two kinds of quality control checks:
Check Using "Test Quality Control Solutions" or "Electronic
Controls". Test quality control solutions and electronic controls
are both used to check the operation of your meter. Test quality control
solutions check the accuracy of the meter and test strip. They may also
give an indication of how well you use your system. Electronic controls
only check that the meter is working properly.
Test quality control solutions have known glucose values. Essentially,
when you run a quality control test, you substitute the test solution
for blood. The difference is that you know what the result should be.
To test your meter with a quality control solution, follow the instructions
that accompany the solution. These will guide you to place a certain
amount of solution on your test strip and run it through your meter.
The meter will give you a reading for the amount of glucose in the sample.
Compare this number to the number listed on the test quality control
solution. If the results of your test match the values given in the
quality control solution labeling, you can be assured the entire system
(meter and test strip) is working properly. If results are not correct,
the system may not be accurate — contact the manufacturer for advice.
Manufacturers sometimes include quality control solution with their
meter. However, most often you must order it separately from a manufacturer
or pharmacy.
Some glucose meters also use electronic controls to make sure the meter
is working properly. With this method, you place a cartridge or a special
"control" test strip in the meter and a signal will appear
to indicate if the meter is working.
Take Your Meter with You to The Health Care Provider's Office.
This way you can test your glucose while your health care provider watches
your technique to make sure you are using the meter correctly. Your
healthcare provider will also take a sample of blood and evaluate it
using a routine laboratory method. If values obtained on the glucose
meter match the laboratory method, you and your healthcare provider
will see that your meter is working well and that you are using good
technique. If results do not match the laboratory method results, then
results you get from your meter may be inaccurate and you should discuss
the issue with your healthcare provider and contact the manufacturer
if necessary.
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User Experiences with Glucose Meters
The FDA's Center for Devices and Radiological Health (CDRH) held a series
of focus groups on blood glucose meter use in 2001. The twenty-two members
participated in six groups. They were all government employees, mostly
from CDRH. They were either people with diabetes or family members of
people with diabetes who were familiar with the use of glucose meters.
Most of the participants in these groups were satisfied with their meters.
Some were quite enthusiastic about the new models. A few had some concerns
about meters. One such participant stated: "The first meter I got
I couldn't use because it was too difficult."
Repeating Tests. Most users repeated tests now and then because
they believed the first test result was incorrect. Users questioned
test results based on their expectations about what the results should
be. If the glucose level seemed "off," they repeated the test.
The ability to judge whether or not a test seemed accurate appeared
to come from the users' experiences with their meters. These experiences
helped them know how they felt when their glucose level was high, when
it was low and when it was about right. They also were aware of what
and when they had eaten, exercised, slept, or taken insulin, and they
learned to anticipate the effect these activities have on their glucose
levels.
Comments users made about their results include the following:
- I sometimes get a reading of perhaps 300 and then 180 on a retest.
This happens in about 1 in 50 tests.
- Glucose tablet residue on my finger can throw results way off.
- I get some inaccurate readings - especially when the meter is new.
- Sometimes I get higher readings than I expect, probably because the
meter was left out of the case or food got on it.
- The date wears off of the vial and I end up using expired strips.
- Humidity around the bathroom seems to affect performance of the strips.
- If I have wet hands, my results tend to be higher than expected.
Besides repeating tests because of a suspected inaccuracy in the
first test, a frequent reason to repeat a test was that the meter
indicated "insufficient blood" on the test strip and would
not complete the test on the first attempt. When this happens, users
needed to do another fingerstick. Users whose meters required less
blood did not have this problem as often.
Feelings about Fingersticks. Surprisingly, most of the participants
stated that fingerstick discomfort was not a big concern - even with
children: "At first, fingersticks were a real problem, but now
it doesn't bother her."
Most participants stated that discomfort was an issue when they first
started to use the meter; this was especially true for children, but
that the discomfort grew less important after a few weeks or months
of use.
However, one participant of a "fragile" child with diabetes
stated: "We test 8 to 10 times a day. He was losing sensitivity
in his fingertips [from the frequent fingersticks]. We prefer the
meter that allows testing in alternative sites."
Use of Test Solution. Most users did not use test solution
often. Some never used it. They stated that the solution was difficult
to use because it expired in a month, it was difficult to order, and
they were not convinced that it helped.
Important Features. Users discussed and rated aspects of meters
such as accuracy, ease-of-use, cost of the meter, cost of test strips,
size, whether it was recommended by a friend etc. The most important
consideration in this group was accuracy. This was followed by "ease
of use" and then affordability.
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New Technologies: Alternative Site Testing
Some glucose meters allow testing blood from alternative sites, such as
the upper arm, forearm, base of the thumb, and thigh
Sampling blood from alternative sites may be desirable, but it may have
some limitations. Blood in the fingertips show changes in glucose levels
more quickly than blood in other parts of the body. This means that alternative
site test results may be different from fingertip test results not because
of the meter's ability to test accurately, but because the actual glucose
concentration can be different. FDA believes that further research is
needed to better understand these differences in test values and their
possible impact on the health of people with diabetes.
Glucose concentrations change rapidly after a meal, insulin or exercise.
Glucose levels at the alternative site appear to change more slowly than
in the fingertips. Because of this concern, FDA has now requested that
manufacturers either show their device is not affected by differences
between alternative site and fingertip blood samples during times of rapidly
changing glucose, or alert users about possible different values at these
times.
Recommended labeling precautions include these statements:
- Alternative site results may be different than the fingertip when
glucose levels are changing rapidly (e.g. after a meal, taking insulin
or during or after exercise).
- Do not test at an alternative site, but use samples taken from the
fingertip, if
- you think your blood sugar is low,
- you are not aware of symptoms when you become hypoglycemic, or
- the site results do not agree with the way you feel.
In October, 2001, FDA held a public meeting to discuss the types of information
and labeling needed for glucose measuring devices if the blood sample
is taken from alternative sites rather than the fingertip. Presenters
included manufacturers of blood glucose meters, healthcare providers,
people with diabetes, and parents of children with diabetes.
For more information about the panel meeting on alternative site testing,
use the following link:
Clinical Chemistry and Clinical Toxicology Devices Panel Meeting Summary
for October 29, 2001
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfAdvisory/details.cfm?mtg=260
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Minimally Invasive and Non-Invasive Glucose Meters
Researchers are exploring new technologies for glucose testing that avoid
fingersticks. One of these is based on near-infrared spectroscopy for
measurement of glucose. Essentially, this amounts to measuring glucose
by shining a beam of light on the skin. It is painless. There are increasing
numbers of reports in the scientific literature on the challenges, strengths,
and weaknesses of this and other new approaches to testing glucose without
fingersticks.
FDA has approved one "minimally invasive" meter and one "non-invasive"
glucose meter. Neither of these should replace standard glucose testing.
They are used to obtain additional glucose values between fingerstick
tests. Both devices require daily calibration using standard fingerstick
glucose measurements and both remain the subject of continuing studies
to find how they are best used as tools for diabetes management.
Metronic MiniMed
Continuous Glucose Monitoring System.
The MiniMed * system
consists of a small plastic catheter (very small tube) inserted just
under the skin. The catheter collects small amounts of liquid that is
passed through a "biosensor" to measure the amount of glucose
present.
The Minimed *
system
is intended for occasional use and to discover trends in glucose
levels during the day. It does not give you readings for individual
tests and therefore you can't use it for typical day-to-day monitoring.
The device collects measurements over a 72-hour period and then must
be downloaded by the patient or healthcare provider. Understanding trends
over time might help patients know the best time to do their standard
fingerstick tests. You need a prescription to buy the * system.…
Cygnus GlucoWatch Biographer. GlucoWatch is worn on the arm
like a wristwatch. It pulls tiny amounts of fluid from the skin and
measures the glucose in the fluid without puncturing the skin. The device
requires 3 hours to warm up after it is put on. After this, it can provide
up to 3 glucose measurements per hour for 12 hours. Unlike the *
device, the GlucoWatch displays results that can be read by the wearer,
although like the * device, these readings are not meant to be
used as replacements for fingerstick-based tests. The results are meant
to show trends and patterns in glucose levels rather than report any
one result alone. It is useful for detecting and evaluating episodes
of hyperglycemia and hypoglycemia. However, you must confirm its results
with a standard glucose meter before you take corrective action. You
need a prescription to buy GlucoWatch.
For more information about GlucoWatch, use the following link:
Cygnus GlucoWatch Automatic Glucose Biographer http://www.fda.gov/cdrh/mda/docs/p990026.html
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How FDA Regulates Glucose Meters
FDA reviews all glucose meters and test strips before they can be marketed
to the public. This FDA "premarket" review process requires
the manufacturer of the meter to show that the meter system provides acceptable
accuracy and consistency of glucose measurement at high, medium and low
levels of glucose as compared to glucose meters already being sold. The
quality of software is an increasingly important feature of glucose meters
since it controls the testing and data storage and controls the displays
that the user sees and uses when testing.
FDA also considers possible interference from over-the-counter medications,
prescription medications, and vitamin supplements.
FDA also asks for data showing how well the meter has performed during
actual use (a type of human factors study). These studies ensure that
users understand the labeling, achieve good results, and avoid experiencing
problems that could affect their health.
For an outline of the FDA review process for glucose meters, use the
following link:
Review Criteria Assessment of Portable Blood Glucose Monitoring In
Vitro Diagnostic Devices Using Glucose Oxidase, Dehydrogenase or Hexokinase
Methodology (Draft Document)
http://www.fda.gov/cdrh/ode/gluc.html
For information about the application of human factors to the design
of medical devices, use the following link:
Medical Device Use Safety: Incorporating Human Factors Engineering
into Risk Management
http://www.fda.gov/cdrh/humfac/1497.pdf
FDA quality system regulations require that manufacturers who make glucose
meters follow the same quality standards every time. In this way, users
can be assured that new meters and strips perform as well as older models.
FDA's responsibility for medical devices does not end when the devices
enters the market. To monitor the quality of products, FDA routinely inspects
manufacturing facilities. It also receives information from the manufacturers,
health providers and the general public through the MedWatch system.
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Reporting Problems with Glucose Meters to FDA
FDA learns about problems with medical products through the MedWatch
program. Consumers can report problems with medical devices, including
glucose meters, through MedWatch.
For general information about the MedWatch program and instructions for
reporting problems with medical devices, use the following link:
MedWatch: The FDA Safety Information and Adverse Event Reporting Program
http://www.fda.gov/medwatch/how.htm
For further information about how medical device problems are reported
to FDA, use the following link:
Reporting Problems with Medical Devices
http://www.fda.gov/cdrh/mdr.html
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Performance Goals for Glucose Meters
Deciding performance standards for glucose meters has been controversial
and challenging. In spite of effort in the late 1970s and 1980s by both
FDA and CDC, no universally accepted standards or testing methods have
been developed for the measurement of glucose. CDC (Centers for Disease
Control and Prevention) recently held a standards conference and is exploring
the possibility of developing a standard reference material for whole
blood.
The ADA has recommended accuracy goals twice over the past twenty years,
once in 1986 (target accuracy of +/- 15%) and once in 1993 (target accuracy
of +/- 5%) No company that manufacturers glucose meters has developed
a cost-effective system to meet these goals. A number of alternative standards
have been suggested by national standards organizations in the U.S., Canada,
and Europe. An international standard ISO DIS 15197 is currently under
development that recommends accuracy of +/- 20 mg/dl for glucose values
under 100 mg/dl and +/- 20% for higher glucose values.
Although data on glucose meters continue to show variable performance,
the newest generations of meters are simpler to use and more accurate
than older models. Improvements in the chemical, mechanical and software
components of glucose meters are continuing to help with the management
of diabetes.
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A Brief History of Self-Monitoring of Blood Glucose
with Glucose Meters
Anton Hubert Clemens received the first patent for a blood glucose meter
called the Ames Reflectance Meter on September 14, 1971. Richard K. Bernstein,
an insulin dependent physician with diabetes, was one of the first patients
to monitor his blood glucose at home using a glucose meter. He published
a report on his experiences in an early volume of the medical journal,
Diabetes Care. He has also written a book on this subject "Dr. Bernstein's
Diabetes Solution: A Complete Guide to Achieving Normal Blood Sugars".
The first articles in the medical literature on the home blood glucose
monitoring were published in 1978 (references 1-5).
These demonstrated that patients could reliably measure their blood glucose
levels at home and improve control of their glucose levels.
In November 1986, the American Diabetes Association, the Centers for
Disease Control and Prevention, the Food and Drug Administration, and
the National Institutes of Health convened a Consensus Conference on Self-Monitoring
of Blood Glucose. The results of that conference was that self-monitoring
of blood glucose was an exciting and important tool for effective management
of patients with diabetes (reference 6).
It was recommended that SMBG be used by patients to accomplish the following
goals:
(a) Keep track of their glucose levels over time,
(b) Help make day-to-day decisions for managing glucose,
(c) Recognize emergency situations, and
(d) Educate themselves on how to manage their blood glucose levels
SMBG was first used because health care providers and researchers believed
that its use would help with glucose control and that better glucose control
would reduce or prevent diabetes complications. In other words, if hyperglycemia
(too much glucose in the blood) and hypoglycemia (too little glucose in
the blood) could be controlled, people with diabetes would remain healthier.
This expectation was shown to be true in 1993, when the National Institute
of Diabetes and Digestive and Kidney Diseases (NIDDK) published results
of a large and conclusive study called the Diabetes Control and Complications
Trial (DCCT), which involved patients at 29 medical centers in the United
States and Canada. In this study, SMBG was an important part of the glucose
control strategy.
This study showed that for persons with type 1 diabetes, intensive treatment
to keep blood glucose levels close to normal reduced the rate of diabetic
complications. In fact, the risk reduction was 76% for eye disease, 50%
for kidney disease, and 60% for nerve disease.
These benefits of tight control of glucose were not problem-free however.
Patients in the intensive treatment group had an increased risk of hypoglycemia.
In September 1993 the American Diabetes Association held a second Development
Conference on Self-Monitoring of Blood Glucose. This conference noted
that SMBG was an important component of the treatment plan of patients
with diabetes mellitus and four major reasons for using SMBG were discussed:
(a) Controlling glucose at a specific, healthy level,
(b) Detecting and preventing hypoglycemia, and severe hyperglycemia,
(c) Adjusting care in response to changes in life-style for individuals
requiring medication, and
(d) Determining the need for starting insulin therapy in gestational diabetes
mellitus (temporary diabetes that happens during pregnancy).
Currently, the market for blood glucose meters is several billions dollars
per year worldwide and growth continues.
References
1. Danowski TS and Sunder JH: Jet injections of insulin during self-monitoring
of blood glucose. Diabetes Care 1:27-33, 1978.
2. Skyler JS et al: Home blood glucose monitoring as an aid in diabetes
management. Diabetes Care 1:150-157, 1978.
3.Sonksen PH, Judd Sl, and Lowy C: Home monitoring of blood glucose- method
for improving diabetic control. Lancet 1: 729-732, 1978.
4. Walford S et al: Self-monitoring of blood glucose — improvement of
diabetic control: Lancet 1: 7320735, 1978.
5. Peterson et al: Feasibility of tight control of juvenile diabetics
through patient-monitored glucose determinations. Diabetes 27(suppl 2):
437, 1978.
6. Ikeda Y et al: Pilot study of self-measurement of blood glucose using
the Dextrostix-Eyetone system for juvenile-onset diabetes. Diabetologia
15:91-93, 1978.
[Top]
Other Diabetes Management Tests
Glycosylated Hemoglobin
There is hemoglobin in all red blood cells. Hemoglobin is the part of
the red blood cell that carries oxygen to the tissues and organs in the
body. Hemoglobin combines with blood glucose to make glycosylated hemoglobin
or
hemoglobin A1c.
Red blood cells store glycosylated hemoglobin slowly over their 120-day
life span. When you have high levels of glucose in your blood, your red
blood cells store large amounts of glycosylated hemoglobin. When you have
normal or near normal levels, your red blood cells store normal or near
normal amounts of glycosylated hemoglobin. So, when you measure your glycosylated
hemoglobin, you can find out your level of blood glucose, averaged over
the last few months.
Doctors have used the glycosylated hemoglobin test for patients with
diabetes since 1976 (1,2). The test is now widely used in the routine
monitoring of patients with diabetes mellitus. Your doctor may use this
test to see how well you respond to treatment. If you have low test values
you probably have lowered risk for having complications from diabetes
mellitus.
It is good to have your glycosylated hemoglobin tested at least two times
a year if you meet your treatment goals or up to four times a year if
you change therapy or do not meet your treatment goals. There are now
many different ways to measure glycosylated hemoglobin. These tests vary
in cost and convenience and you can do some at home. The values (glycosylated
hemoglobin index) these tests give can vary too. Talk to your doctor about
what your glycosylated hemoglobin index should be.
Patients with diseases affecting hemoglobin, such as anemia, may get
wrong values with this test. Vitamins C and E, high levels of lipids,
and diseases of the liver and kidneys may all cause the test results to
be wrong.
References
1. Bunn HF, Haney DN, Kamin S, et al: The biosynthesis of human hemoglobin
A1C: slow glycosylation of hemoglobin in vivo. J Clin Invest 57(6):1652-9,
1976.
2. Fabbay KH: Editorial: Glycosylated hemoglobin and diabetic control.
N Eng J Med 295(8):443-4, 1976.
For more information about the glycosylated hemoglobin test (HbA1c),
use the following links:
Medlineplus Healthline Health Information, Medical Encyclopedia, Glycosylated
Hemoglobin
http://www.nlm.nih.gov/medlineplus/ency/article/003640.htm
National Diabetes Education Program — HbA1c Quiz and Answers
http://ndep.nih.gov/materials/pubs/HbA1c/HbA1c-checkIQ.htm
Glycosylated Hemoglobin
http://www.healthy.net/library/books/textbook/section2/glyhem.pdf
Review Criteria for Assessment of Glycohemoglobin (Glycated or Glycosylated)
Hemoglobin In Vitro Diagnostic Devices
http://www.fda.gov/cdrh/ode/odecl658.html
The National Glycohemoglobin Standardization Program (NGSP)
http://www.missouri.edu/~diabetes/ngsp.html
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Glycosylated Serum Proteins
Serum proteins, like hemoglobin, combine with glucose to form glycosylated
products. Testing these glycosylated products can give information about
your glucose control over shorter periods of time than testing glycosylated
hemoglobin.
One common test is the fructosamine test. It gives information on your
glucose status over a one- to two-week period. High values mean your blood
glucose was high over the past two weeks. This test is good for watching
short-term changes in your glucose status during pregnancy or after major
changes in your therapy. There is no general guideline for when to use
this test. Talk to your doctor about whether this test is right for you.
If you have any other disease that can change your serum proteins or
if you have large amounts of Vitamin C (ascorbic acid) in your diet, these
tests may give wrong values.
For more information about the fructosamine test, use the following link:
Technical and Clinical Evaluation of Fructosamine Determination in
Serum.
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http://www.cdc.gov/diabetes/pubs/economics/biblio_1-2.htm
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Urine Glucose
Only patients who are unable to use blood glucose meters should use urine
glucose tests. Testing urine for glucose, which was once the best way
for patients to manage their diabetes, has mostly now been replaced by
self-monitoring of blood glucose. There are three major drawbacks of urine
glucose testing compared to blood testing. First, urine glucose testing
will not tell you about low (below 180 mg/dl) glucose levels, since at
lower levels glucose does not enter your urine. Second, urine glucose
readings change when the volume of your urine changes. Third, your urine
glucose level is more of an average value than your blood glucose level.
There are several dipstick tests available on the market.
For more information about measuring glucose in urine, use the following
link:
Medlineplus Healthline Health Information, Medical Encyclopedia, Glucose-Urine
http://www.nlm.nih.gov/medlineplus/ency/article/003581.htm
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Urine and Blood Ketones
When the body does not have enough insulin, fats are used for fuel instead
of glucose. A by-product of burning fats is the production of ketones.
Ketones are passed in the urine and can be detected with a urine test.
If you do not have diabetes, you usually have only small amounts of ketones
in your blood and urine. If you have diabetes, however, you may have high
amounts of ketones and acid, a condition known as ketoacidosis. This condition
can cause nausea, vomiting, or abdominal pain and can be life threatening.
You may use urine dipsticks to rapidly and easily measure the ketones
in your urine. You dip a dipstick in your urine and follow the instruction
on the package to see if you have a high amount of ketones.
If you have type 1 diabetes, are pregnant with preexisting diabetes,
or who have diabetes caused by pregnancy (gestational diabetes), you should
check your urine for ketones. If you have diabetes and are ill, under
stress, or have any symptoms of high ketones, you should also test your
urine for ketones.
Results of ketone testing should be interpreted with care. High ketone
levels are found when patients are pregnant (in the first morning urine
sample), starving, or recovering from a hypoglycemic episode.
There are now tests for measuring ketones in blood that your doctor
may use or you can use at home. Some measure a specific ketone (beta-hydroxybuyric
acid) that patients with diabetic ketoacidosis may have.
It is still not known which type of ketone test -blood or urine — offers
more aid to people with diabetes.
For more information about ketone tests, use the following links:
Medlineplus Healthline Health Information, Medical Encyclopedia, Ketones-Urine
http://www.nlm.nih.gov/medlineplus/ency/article/003585.htm
Medlineplus Healthline Health Information, Medical Encyclopedia, Serum
Ketones
http://www.nlm.nih.gov/medlineplus/ency/article/003498.htm
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Microalbumin
One common and extremely serious result of diabetes is kidney failure.
Under normal conditions, the kidneys filter toxins from the blood. When
the kidney's filtering processes begin to become impaired, protein (microalbumin)
begins to spill into the urine. Testing urine for small, yet abnormal
amounts of albumin (microabluminuria) is a common way to detect this condition
early, before it can damage your kidneys.
Many urine dipsticks are used to test for large amounts of albumin. To
measure a small amount of albumin, which may show an early stage of kidney
disease, your health care provider may use specific tests for low levels
of albumin (microalbumin tests). To do this test, you may have to collect
your urine for several 24-hour periods.
The ADA recommends that adults with diabetes be tested for microalbumin
every 3- to 6-months. The ADA recommends testing in children with type
1 diabetes at puberty or after having diabetes for 5 years.
Early detection of microalbumin is important because it indicates increased
risk for both renal and vascular disease. Fortunately, early detection
allows for treatments that may delay the beginning of a more serious disease.
For more information about microalbumin tests, use the following link:
Medlineplus Healthline Health Information, Medical Encyclopedia, Microalbuminuria
http://www.nlm.nih.gov/medlineplus/ency/article/003591.htm
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Cholesterol
If you have diabetes, you have a higher risk of heart and blood vessel
disease (cardiovascular disease). One way to limit this risk is to measure
your cholesterol routinely and control it by changing your lifestyle or
taking prescription drugs. A cholesterol test usually shows your total
cholesterol, total triglycerides, and high-density lipoproteins (HDLs).
The Centers for Disease Prevention and Control (CDC) has set up a National
Reference System for Cholesterol Testing and many manufacturers verify
their test through certification with this method.
For more information about cholesterol testing, use the following link:
Medlineplus Healthline Health Information, Medical Encyclopedia, Cholesterol Test
http://www.nlm.nih.gov/medlineplus/ency/article/003492.htm
* now known as
Medtronic MiniMed
From the
Food and Drug Administration
http://www.fda.gov/diabetes/glucose.html
Updated 5/1/02
