Key Points

• A number of medications may cause your blood glucose levels to change when you have diabetes. Always tell your doctor that you have diabetes and what medication you take for your diabetes when they are prescribing medication
• Your dose of blood-glucose lowering medication (insulin or sulphonylureas) may need to be changed if you go onto one of these medications
• Test your blood glucose frequently if you are starting on a medication that may change your blood glucose levels
• Some medications come suspended in a syrup form. These syrups are often high in sugar. Check with the chemist whether they can give you a 'no sugar added' alternative
• Street drugs or marijuana may also cause changes to your blood glucose levels

Sometimes you may need medications for other things besides your diabetes. Some medications can affect your blood glucose levels. It pays to know what these medications are. Sometimes there is an alternative medication available that will not have the same effect. Sometimes you may need the medication anyway. But if you can anticipate the effect they may have on your blood glucose levels it will allow you to plan to manage this.

This section lists some of the commonest medications that may alter the action of the blood-glucose lowering medications you are on. It is not a complete list and you should always check with your doctor when you are starting any new medication.

Drugs that may put your blood glucose up

The most common group of medications that may cause a big increase in your blood glucose levels is steroids.

Steroids are generally prescribed to dampen down inflammation. They are an extremely useful group of drugs and they are very effective in what they do. For some situations steroid medication is exactly what you may require. They are often used for people with arthritic conditions, for people with asthma or chest problems and for people with tissue swelling that's causing major problems for them.

Unfortunately, these very useful drugs will also make your blood glucose levels go high. In fact many people first find out they have diabetes when they have been started on steroids for another reason and their blood glucose levels suddenly become high.

Why do steroids put my blood glucose up?

The way steroids put your blood glucose up is exactly the way stress hormones do. In fact one of the natural stress hormones we all produce is called 'glucocorticosteroid'. This hormone is a steroid.

Steroids cause your blood glucose to go high because they do two things:

• They block the action of your insulin where it moves glucose out of your blood stream and into your body cells
• They cause your liver to start manufacturing extra glucose to release into your blood. Both these actions cause your blood glucose to rise

Because you have a limited ability to release extra insulin to start moving this extra glucose into your cells and muscles, your blood glucose goes high.

What should I do if I am prescribed steroids?

Firstly, tell the doctor who is prescribing the steroids that you have diabetes. He or she may decide to try another group of drugs. Or, if they feel you really need the steroids, they will want to make a plan with you as to how to manage your blood glucose levels while you are taking the steroids.

When you start on steroids you should immediately start testing your blood glucose levels frequently (if you are not already doing so). Four or more times a day is ideal. That way you can see what is happening. If you are not already testing your own blood glucose levels you should arrange to get a blood glucose meter and be taught how to use it and when to test. Visit the glucose meters & diabetes management section of this web site for more information.

If you are taking insulin it will almost certainly be necessary for you to increase your dose of insulin while you are on the steroids. The increase you make should be in response to what your blood glucose levels are. Work with a diabetes nurse educator or diabetes specialist to work out how to increase your insulin at this time.

If you take sulphonylurea or other tablets for your diabetes you may need help from your nurse or doctor to increase these.

Remember, however, that there is a maximum dose of these tablets that you should not go beyond. Often increasing your sulphonylurea tablets when you are on steroids doesn't have much effect in bringing your blood glucose levels down. Many people on sulphonylurea tablets manage better if they go onto insulin for the time they need the steroid medication.

Steroid medication is not usually given long term. You usually go on it for a course until the problem that the steroids are treating has settled down. Unless you are on a very low dose of steroids they won't be stopped straight away. The best way to stop steroid medication is to slowly reduce it over time.

If you have had to increase your diabetes medication during the time you are on steroids you will almost certainly find that you will need to reduce it again as you come off the steroids. Once again, your blood glucose levels will tell you if this needs to happen. They will start to drop as the steroids are tailed off. Work closely with your diabetes nurse educator and/or doctor to get help to reduce your diabetes medication during this time.

Other drugs that can cause your blood glucose to go up

Some oral contraceptive medications

Some oral contraceptives can cause your blood glucose levels to increase. The ones that can have this effect are ones that either have a high level of oestrogen in them, or those that contain levonogestral. Progesterone-only oral contraceptives tend to have very little effect on your blood glucose levels and are a better option.

Thiazide diuretic tablets

In high doses these medications can cause your blood glucose levels to go up. These drugs are usually only prescribed in low doses for people with diabetes.

Salbutamol (or ventolin) tablets

Salbutamol tablets can cause your blood glucose levels to go up. Salbutamol is prescribed for asthma.

Phenytoin (or dilantin) tablets

This drug is often prescribed for epilepsy and it can cause your blood glucose levels to go up.

Drugs that may cause blood glucose-lowering medication to work too hard

Some medications or drugs can cause your blood glucose to go too low if you are taking diabetes medication that is able to cause low blood glucose levels (insulin or sulphonylureas).

The most common of these drugs is alcohol.

Alcohol

If you take insulin or sulphonylurea tablets alcohol can put you at risk of having a serious low blood glucose level. When you take these medications you should (as far as possible) drink in moderation only. You should also never drink on an empty stomach. For more on managing alcohol safely when you are on these medications visit alcohol and diabetes.

Warfarin

Warfarin is an 'anticoagulant' or blood-thinning agent that is often prescribed for people who are at risk of forming clots in their blood vessels. Taking warfarin can cause your blood glucose levels to go low if you take sulphonylurea tablets.

If you need to go onto warfarin make sure your doctor and the nurses that help you manage on warfarin know you take sulphonylurea tablets. Monitor your blood glucose levels more frequently until your blood glucose levels are settled on the warfarin.

MAO Inhibitors

Some people take MAO Inhibitors for psychiatric illnesses. MAO Inhibitors make sulphonylurea tablets work more strongly. Make sure your doctor knows you are on sulphonylurea tablets if they are prescribing you MAO Inhibitors.

Some antibiotics

Chloramphenicol, tetracycline and the sulphonamide group of antibiotics can cause sulphonylurea medication to have a stronger effect. If you are going onto antibiotics make sure your doctor knows you are on sulphonylureas and also monitor your blood glucose levels more often.

Drugs that may cause unpredictable changes in your blood glucose levels

Taking street drugs or marijuana can indirectly cause alterations in your blood glucose levels. They may cause you to be unable to recognise the symptoms of low blood glucose levels or to mistake them for the effects of the drug. This can put you at risk of having a serious low blood glucose level if you take either insulin or sulphonylureas. This is because you may not be alert enough to recognise or correct the low blood glucose level.

Some street drugs may cause you to eat either more food or less food. Many people feel the need to eat a great deal when they take marijuana.

Some party drugs (e.g., ecstasy) may cause you to feel as though you have boundless energy and can dance all night without feeling the need for rest or food. If you are on insulin or sulphonylureas this can be very dangerous as it can lead you to have a very serious hypo.

You may also be more likely to have a serious hypo when you are away from your normal family and friends. The people you are with may think you have collapsed as a result of the drug - or just being exhausted - and not recognise that your blood glucose is low and you need urgent treatment.

Street drugs also come in very unpredictable strengths. It is often not possible to anticipate what kind of effect they will have on you, even if you have taken the drug before. The dose of the drug you are about to take may be either stronger or weaker than the last dose you took, and you have no way of knowing this.

For all these reasons it is not safe for you to experiment with taking these drugs. However, if you are taking these kind of drugs it is often helpful to find a diabetes nurse educator or diabetes medical specialist with whom you feel comfortable to discuss the safety issues around use of these drugs. Your GP may also be able to help.