This information is for people who have type 2 diabetes. It tells you about sulphonylureas, a treatment used for type 2 diabetes. It is based on the best and most up-to-date research.
Do they work?
Yes. Sulphonylureas can help you control the level of glucose (sugar) in your blood if you have type 2 diabetes.
And you may be less likely to get low blood glucose ( hypoglycaemia) if you take a newer sulphonylurea rather than an older one.
What are they?
Sulphonylureas are a group of drugs that lower the amount of glucose (sugar) in your blood. They come as tablets. You need a prescription from your doctor to get these tablets.
Your doctor may prescribe a sulphonylurea drug on its own, or you might take it along with other drugs to treat your diabetes. For more, see Taking two drugs together.
Your doctor is more likely to give you a sulphonylurea drug if you're not overweight, or if you can't take another drug called metformin. 
Some sulphonylureas (and their brand names) are listed below.
How can they help?
If you take an older sulphonylurea like glibenclamide, your haemoglobin A1c level may be about one point lower over 10 years than if you just watch what you eat.   Doctors use the haemoglobin A1c blood test to see how well you are controlling your diabetes.
A newer sulphonylurea (glimepiride or glipizide) can also help to lower your haemoglobin A1c level.
A newer sulphonylurea is likely to work as well as an older one.
How do they work?
Sulphonylureas make your pancreas put more insulin into your bloodstream. Insulin is a hormone that helps glucose move from your bloodstream into your cells. This helps keep your level of glucose steady.
Can they be harmful?
If you take a sulphonylurea, you may gain weight.
Over 10 years you may gain about 2 kilograms to 3 kilograms more (about 5 pounds more) than if you just watched what you ate. 
The newer sulphonylurea glimepiride may cause a weight gain of about 5 kilograms (about 10 pounds) over three months. 
If you take a sulphonylurea you might also be more likely to get low blood glucose (hypoglycaemia) than if you just eat healthily.  But you may be less likely to get hypoglycaemia with a newer sulphonylurea (such as glimepiride) than with an older one (such as glibenclamide).      Your chance of getting low blood glucose may be about 20 percent to 30 percent less.  
You might get an allergic reaction in the first six weeks to eight weeks of treatment. This would probably affect your skin. You might get a rash or itchy red bumps. If this happens, you might need to switch to another treatment. If you are allergic to drugs containing sulphur compounds, you should not take sulphonylureas.