Insulin is a hormone made in your pancreas. It helps your body use glucose (sugar) for energy. In type 1 diabetes your pancreas no longer makes insulin or cannot make enough insulin, so you have to inject it to control your blood glucose levels.
There are different types of insulin, taken at different times.
Insulin taken once or twice a day
This is called long-acting, background, or basal insulin.
It gives your body the insulin it needs whether you eat or not. Basal insulin should keep your blood glucose stable overnight and between meals. It is important that you never miss your basal insulin.
Insulin taken with food or drink
This is called fast-acting, mealtime or bolus insulin.
It helps reduce the rise in blood glucose caused by eating or drinking. You usually take it before a meal, snack or drink that has carbohydrates in it.
The Irish Nutrition and Dietetic Institute have a booklet on Eating well with type 1 diabetes (PDF, 39 pages 1.8KB)