As a class of medication used to treat type 2 diabetes, biguanides lower blood sugar in two ways. Their primary action is to reduce the amount of sugar produced by the liver. In addition, they can also increase the amount of sugar absorbed by muscle cells and decrease insulin resistance. According to the federal Agency for Healthcare Research and Quality (AHRQ), biguanides can lower A1c levels by one point and may also decrease levels of bad cholesterol more than other diabetes medications.
Who should use biguanides?
Individuals who are unable to control their blood glucose levels with diet or exercise alone may be prescribed a biguanide medication. Drugs in this class may be taken alone or combined with another medication such as a sulfonylurea. In addition, biguanides may be used to improve the effectiveness of insulin therapy.
Biguanides have been shown to be effective in treating children and adolescents diagnosed with type 2 diabetes. In some cases, biguanides may be used to treat pre-diabetes. This class of medications is not recommended for those with very low insulin levels as well as those with serious medical conditions such as kidney, lung or liver disease. Those preparing for major surgery also should not take a biguanide.
Medications in the biguanide class
Metformin is the only biguanide medication currently available. As an individual medication, it sold under several brand names, including the following:
- Glucophage and Glucophage XR
There are also several combination medications available that include both metformin and another medicine. These include the following brand name drugs:
- Metaglip (glipizide and metformin)
- Glucovance (glyburide and metformin)
- Prandimet (repaglinide and metformin)
- Avandamet (rosiglitazone and metformin)
Common biguanide side effects and dosages
As a single drug, metformin can be administered as either a tablet or a liquid. While some medications are extended release and may be taken daily, other forms of metformin may be used up to three times daily. The AHRQ reports metformin may cause less weight gain than other medications prescribed for type 2 diabetes. However, there is a higher risk for stomach problems such as gas or diarrhea. These side effects may be minimized by taking the medication with food.
In addition to the common side effects, metformin medications carry a black box warning from the Food and Drug Administration. An accumulation of metformin can cause lactic acidosis. This is a rare complication but when it occurs, it can be fatal in 50 percent of cases.
Important: Before taking metformin or any other medication, individuals should consult with a physician or other health care professional.
AHRQ, "Medicines for Type 2 Diabetes: A Review of the Research for Adults,"
American Diabetes Association, "What Are My Options?"
WebMD, "Biguanides for Type 2 Diabetes"