What is diabetes? Dr Rob Hicks Diabetes is currently an incurable condition in which too much glucose (sugar) is present in the blood. Find out more about the different types and how it's treated.

In this article

A common problem

What's the difference?

Normal blood sugar control

Diabetes occurs because the body can't use glucose properly, either owing to a lack of the hormone insulin, or because the insulin available doesn't work effectively.

The full name 'diabetes mellitus' derives from the Greek word 'diabetes' meaning siphon - to pass through - and 'mellitus' - the Latin for honeyed or sweet. This is because not only is excess sugar found in the blood but it may also appear in the urine, hence it being known in the 17th century as the 'pissing evil'.

Diabetes has been a recognised condition for more than 3,500 years.

According to the charity Diabetes UK, more than 2 million people in the UK have the condition, and up to 750,000 more are believed to have it without realising they do.

More than three-quarters of people with diabetes have what is called type 2 diabetes mellitus.This used to be known as non-insulin dependent diabetes mellitus (NIDDM) or maturity-onset diabetes mellitus.

The remainder have type 1 diabetes mellitus, which used to be known as insulin-dependent diabetes mellitus.

• In type 1, the body's unable to produce any insulin. This usually starts in childhood or young adulthood. It's treated with diet control and insulin injections.
• In type 2, not enough insulin is produced or the insulin that is made by the body doesn't work properly. This tends to affect people as they get older, and usually appears after the age of 40.

The body converts glucose from food into energy. Glucose comes ready made in sweet foods such as sweets and cakes, or from starchy foods such as potatoes, pasta or bread once they're digested. The liver is also able to manufacture glucose.

Under normal circumstances, the hormone insulin, which is made by the pancreas, carefully regulates how much glucose is in the blood. Insulin stimulates cells to absorb enough glucose from the blood for the energy, or fuel, that they need. Insulin also stimulates the liver to absorb and store any glucose that's left over.

After a meal, the amount of glucose in the blood rises, and this triggers the release of insulin. When blood glucose levels fall, during exercise for example, insulin levels fall too.

A second hormone manufactured by the pancreas is called glucagon. It stimulates the liver to release glucose when it's needed, and this raises the level of glucose in the blood.

Insulin is manufactured and stored in the pancreas, which is a thin gland about 15cm (6in) long that lies crosswise behind the stomach. It's often described as being two glands in one, since in addition to making insulin it also produces enzymes that are vital for digestion of food.

These include lipase, which helps to digest fat, and amylase that helps to digest starchy foods. It also releases 'bicarbonate of soda' to neutralise any stomach acid that may otherwise damage the lining of the gut.

This article was last medically reviewed by Dr Roger Henderson in January 2009.
First published in April 2001.