In people without diabetes, insulin is stored in the pancreas and released into the blood as soon as the blood glucose level starts to rise after eating. Insulin is released straight into the liver where it has the important role of regulating glucose production and promoting the storage of glucose as glycogen. The level of glucose in the blood then falls and, as it does so, insulin production is switched off (see Figure 1.2). Thus people who do not have diabetes have a very sensitive system for keeping the amount of glucose in the blood at a steady level. In diabetes this system is faulty. People with Type 2 diabetes can still produce some insulin but not in adequate amounts to keep the blood glucose level normal. This is because their insulin does not work properly (a condition called ‘insulin resistance’). People with Type 1 diabetes have little or no insulin of their own and need injections of insulin to try to keep the blood glucose level normal. Even if given four or five times a day, an injection of insulin is not as efficient at regulating blood glucose as the pancreas, which responds to small changes in blood glucose by switching the insulin supply on or off at a moment’s notice.
There are three main factors affecting your blood glucose:

• Food (which puts it up)
• Insulin
• Exercise (which both bring it down).

Any form of stress, in particular an illness like ’flu, puts up your blood glucose. Learning how to balance your blood glucose level is a matter of trial and error. This involves taking a lot of measurements and discovering how various foods and forms of exercise affect your blood glucose. In the past, people with Type 1 diabetes were brought into hospital to be ‘stabilized’ on a certain dose of insulin. Experience has shown that the insulin needed in the artificial surroundings of a hospital ward bears little relation to the amount needed in someone leading an active life in the outside world. Nowadays, you can ‘stabilize’ your own diabetes at home yourself.