In healthy people, insulin is secreted at a constant, low level over 24 hours. This prevents glucose release by the liver, which may occur via the processes of gluconeogenesis (when glucose is produced from non-carbohydrate sources such as amino acids) and glycogenolysis (when the carbohydrate, glycogen, is broken down into glucose).
Increases in insulin secretion occur during mealtimes when the digestion of food leads to an increase in blood glucose. The insulin helps to keep the blood-glucose levels in a normal range.
In type 1 diabetics, the aim is to mimic normal insulin secretion, which is best done by the so-called "basal bolus regimen".
This means that a long-acting insulin such as Lantus or Levemir is given once a day, at the same time (for example at 21:00). This is to provide a 24-hour basal insulin supply .The aim is to keep the fasting blood glucose between 4 and 7mmol/l.
Rapid-acting or short-acting insulin is then taken before meals to cover meal-time surges in glucose. This usually involves a further three injections during the day.
So, the basal bolus regimen usually involves four injections per day. It gives the diabetic some flexibility, better blood-glucose control and fewer hypoglycaemic episodes (when there's too little glucose in the bloodstream), especially if the insulin analogues are used.
Another regimen is to use a twice-daily premixed insulin at breakfast and supper. However, in some diabetics a third dose may be needed at lunchtime.
Doses are best worked out by the prescribing doctor and sometimes by a diabetic nurse. Note that every diabetic has his or her own appropriate dose. Don't compare your dose to that of another diabetic as his or her circumstances may be very different to yours.
Reviewed by Dr Suresh Rajpaul (MbChB, FCPsa)