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If you have diabetes, you have too much glucose in your blood. Glucose is a kind of sugar your body uses for energy. It can build up in your blood and make you sick. Normally, the amount of glucose in your blood is controlled by a hormone called insulin.

There are two main types of diabetes: type 1 and type 2.

• If you have type 1 diabetes, your body doesn't make a hormone called insulin. You need to have regular shots of insulin to keep your blood sugar under control. To read more, see Type 1 diabetes.
• If you have type 2 diabetes, your body may not make enough insulin, and the insulin it does make doesn't work well enough. You may be treated with a diet, pills or insulin shots to keep your blood sugar under control. To read more, see Type 2 diabetes.

About 9 in 10 people with diabetes have type 2 diabetes.

Over time, too much glucose in your blood can damage the big blood vessels that carry blood around your body. This can lead to serious health problems such as a heart attack, a stroke, or poor circulation in your legs.

Too much glucose can also damage the small blood vessels in your eyes, kidneys and nerves. These are called microvascular complications. But the information here is about how to prevent damage to the big blood vessels (macrovascular complications).

You have a heart attack when blood can't get to your heart muscle. This happens when one of the vessels taking blood to your heart muscle suddenly gets blocked. If your heart muscle doesn't get the blood it needs, part of it dies. This means the heart may not be able to pump properly, to get blood and oxygen around the body.

Heart attacks are life-threatening and you need to get medical help quickly.

A stroke happens when the blood supply to part of your brain is cut off. This can cause brain damage. Strokes affect people in different ways, depending on which part of your brain is damaged. If you have a stroke you may not be able to move one side of your body, or you may have difficulty speaking or swallowing. It can take a long time to recover from a stroke, and some people don't recover fully. To read more, see our information on strokes.

Strokes are life-threatening and you need to get medical help quickly.

Some people with diabetes have poor circulation in their arms and legs. Doctors call this peripheral vascular disease. If you have poor circulation, your legs may not get enough blood flow when you walk. This can be painful. Also, any cuts or broken skin on your feet or legs may take longer to heal up. They may turn into ulcers. To read more, see our information on peripheral vascular disease.

Many people with diabetes have other kinds of health problems which also increase the chance of getting strokes, heart attacks, or circulation problems. These are called risk factors. Risk factors are things that make you more likely to get a health problem. Some of these risk factors are:

• High cholesterol
• High blood pressure
• Being overweight or obese, especially if you have a lot of fat around your waist
• Getting too little exercise.^{1 2}

Your chance of getting heart and circulation problems is also higher if:³

• You have had diabetes as an adult for a long time
• You have diabetes and the level of sugar in your blood is not well controlled
• You have higher than usual levels of protein in your urine. This is a sign that your kidneys have been damaged, perhaps from high blood pressure.^{3 4 5 6}

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.