Drugs for Diabetes Mellitus

Drugs used to treat diabetes mellitus that control blood glucose (sugar) levels

Common drugs



  • Metformin

    Sulphonylurea drugs

  • Glibenclamide

  • Gliclazide

  • Glimepiride

  • Glipizide

  • Tolbutamide

    Other drugs for diabetes

  • Acarbose

  • Glucagon

  • Nateglinide

  • Pioglitazone

  • Repaglinide

  • Rosiglitazone

In diabetes mellitus, levels of blood glucose are too high because the body produces too little or is resistant to the action of the hormone insulin, which is secreted by the pancreas and regulates blood glucose. Drugs for diabetes mellitus keep blood glucose at normal levels.

There are two types of diabetes mellitus. In type 1 diabetes, the body does not produce sufficient insulin, and synthetic insulin is needed. In type 2 diabetes, the body tissues have reduced sensitivity to the action of insulin. Mild forms of type 2 diabetes may be controlled by making changes to the diet and without having to use drugs.

What are the types?

The main drugs for diabetes mellitus are insulin, which is always given for type 1, and antidiabetic drugs, which are used to treat type 2. The most common antidiabetic drugs are metformin and the sulphonylureas, although the drugs acarbose, repaglinide, nateglinide, and the glitazones (pioglitazone and rosiglitazone) may also be prescribed. If antidiabetic drugs are ineffective, insulin may be used to treat type 2 diabetes.


Injections of insulin are given to replace missing natural insulin. This replacement mimics the body’s normal patterns of insulin production, maintaining low background levels with peaks at meal times when glucose enters the blood. Most insulin is genetically engineered to be identical to human insulin.

There are several types of insulin preparation whose durations of action differ. Short-acting insulins are taken 15–30 minutes before meal times, giving high levels of insulin in the blood to coincide with high levels of glucose. Longer-acting insulins are taken once or twice a day. Many people take a combination of both types. The dose will be tailored to your individual needs.

Since insulin is destroyed by stomach acids it cannot be taken orally and is always injected. Your doctor or nurse will teach you how to inject insulin (see Injecting insulin), and you will be shown how to measure your blood glucose levels (see Monitoring your blood glucose). You should measure your glucose levels at regular intervals during the day to see whether your insulin dose is at the correct level. For type 1 diabetes that is hard to control, newer types of long-acting insulin may be appropriate. Alternatively, if these long-acting insulins do not provide adequate control, continuous and timed doses of insulin can be given by a pump.

Taking excess insulin or too little food may cause hypoglycaemia, in which blood glucose levels are abnormally low. You will be taught how to recognize the symptoms, which include sweating, hunger, faintness, and anxiety. If you have an attack, you should eat or drink something sweet immediately. An injection of glucagon, which increases blood glucose levels, may be given for severe hypoglycaemia. Common injection sites for insulin include the abdomen and thighs. Some of the preparations used contain an additive that can cause soreness and inflammation at the injection site when you start using insulin, but this is usually temporary.


Metformin is the drug of first choice for most people with type 2 diabetes and is particularly useful for those who are overweight or those of normal weight whose diabetes cannot be controlled by dietary changes alone. It can be used together with sulphonylureas or another drug such as one of the glitazones to increase the sensitivity of body tissues to insulin. Metformin also increases the utilization of glucose by the tissues.

Metformin is unlikely to cause weight gain and is less likely to cause an attack of hypoglycaemia than sulphonylureas, but it may initially cause nausea, diarrhoea, abdominal bloating, low appetite, and facial flushing. These side effects often disappear after a few weeks of use.

Sulphonylurea drugs

These drugs stimulate the insulin-producing cells in the pancreas to increase insulin production (see How sulphonylurea drugs work). This helps to compensate for the low sensitivity of body tissues to insulin that occurs in type 2 diabetes. Sulphonylurea drugs are usually taken orally once or twice a day, and treatment is combined with dietary restrictions. However, in many people, increased appetite and weight gain are side effects.

Other drugs for diabetes

In addition to other treatments for type 2 diabetes, your doctor may prescribe drugs such as acarbose, repaglinide, nateglinide, or the glitazones. Acarbose slows the absorption of glucose from the intestines and prevents a rapid rise in blood glucose levels after meals. Repaglinide and nateglinide stimulate the release of insulin from the pancreas. These drugs may cause side effects in some people, including flatulence, abdominal discomfort, diarrhoea, and rarely, rashes. Pioglitazone and rosiglitazone increase the uptake of insulin by body tissues, leading to a reduction in blood glucose levels. They may cause side effects including intestinal disturbances, weight gain, headache, and anaemia. Rosiglitazone and pioglitazone should not be used by people with heart failure or a history of heart failure, and may not be suitable for those with other heart problems or peripheral vascular disorders.

Drug Action: How Sulphonylurea Drugs Work

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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