Introduction to insulin dose adjustment

David Kinshuck









What is diabetes requiring insulin... type 1 and type 2?

Insulin is a hormone made in the islet-cells of the pancreas. In type 1 diabetes, the islet cells are severely damaged and no insulin is produced. In more severe types of type 2 diabetes, the islet cells are also severely damaged, although they may produce a tiny amount of insulin.

Generally people with type 1 diabetes or severe type 2 need to inject insulin 2-5 times day. Insulin controls the blood glucose level. Blood glucose is known as blood sugar, but on most of this web site the term blood glucose is used.

Normal blood glucose in non-diabetics is 3.5-6.7 mmol/l before meals and less than 8 mmol/l after eating. Use a sensor to test: glucose sensors are ideal : Freestyle or Dexcom.


What does insulin do?

When blood glucose rises in someone without diabetes, the beta cells in the pancreas gland release insulin into the blood. The insulin reaches the rest of the body and allows glucose from the blood to enter cells. This reduces blood glucose levels and keeps it in the normal range.

Without insulin treatment people with type 1 diabetes cannot keep their blood glucose in the normal range. Levels above 11mmol/l indicate diabetes. The high blood glucose levels are harmful over the years, damaging eyes and kidneys and nerves etc.


Insulin and food

The highest sugar levels occur as you eat and just after a meal, and a normal pancreas secretes half its insulin as a 'bolus' after eating. To replace this insulin you need a quick acting insulin. In the basal bolus regime, the quick acting insulin is be given just as you start each meal, and (at least in theory) prevents the sugar level rising much. Eventually insulin pumps may take over injections, but they are not perfect and not widely available in the UK.

The amount of insulin injected has to match the carbohydrate equivalent of food as below.It allows us to use the glucose from food for energy. Food is divided into 3 main groups:




Foods containing mostly protein or fat do do not directly affect blood glucose levels. On the other hand, foods with carbohydrate are broken down to glucose. Glucose is essential to provide the body cells with energy. The body cells can only take up glucose when enough insulin is present in the blood. Not all the glucose is used immediately. Some is stored in the liver.

The amount of insulin released increases according to how much carbohydrate is eaten. To a lesser degree, insulin also controls the breakdown of body fat and protein. Someone with type 1 or more severe type 2 diabetes produces very little or no insulin. And without insulin, as the glucose cannot enter cells it remains in the bloodstream, and hence the blood glucose levels rises.

Matching the insulin dose with food is discussed on related pages. Only when do insulin dose match the food (especially carbohydrate) intake, will the blood glucose stay at a normal low level.


Basal insulin requirement

The other half of the insulin secreted by the pancreas is secreted gradually during the day and night. This is the so called 'basal' secretion. To replace this insulin, you need a long-acting insulin that works when you are not eating. Essentially, the dose of this long-acting (or background) insulin depends on


You need much less insulin when you exercise, because exercise allows glucose to enter the muscle cell for immediate use. In away exercise acts in a similar way to insulin itself. The dose of insulin if you exercise is much less than if you don't. See exercise for details.



When blood glucose levels rise too high, symptoms may develop. These include:

People with diabetes will not experience all these symptoms, but often some symptoms occur when you are first diagnosed. Glucose appears spills over into the urine when >10mmol/l. The kidneys try to correct the high glucose by making diluting the glucose in the urine. The produces large amounts of urine and leads to dehydration and thirst.

Without insulin, the body cells cannot use glucose for energy. Muscle and fatty tissue are broken down instead. This produces part of the weight loss and produces the ketones found in urine and blood. Some of the weight loss is from the dehydration from the increased urine. Some of the symptoms above are from the high ketone levels.