Introduction to insulin dose adjustment
insulin dose pages from DAFNE
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.
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.
- At meal times the pancreas makes extra insulin to cope with food intake.
- small amounts of insulin are produced continuously providing a background
insulin level...to keep cells supplied with glucose day & night.
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
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:
- starchy foods (eg bread, rice, pasta, potatoes)...these are complex
- and sugary foods (e.g. sweets, biscuits, cakes)
- and fresh fruit
- is found in eggs, meat, fish, cheese, nuts, pulses (lentils,
- is the main component of butter, margarine, cooking oils, mayonnaise,
- hidden in other foods such as various meats, cakes
- there are healthy fats in fish etc
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. This is discussed in
detail. Essentially, the
dose of this long-acting (or background) insulin depends on
- your body mass and fat
- the amount of exercise
- how much remaining insulin your pancreas secretes
- whether or not you are ill, stressed, and other factors
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
blood glucose levels rise too high, symptoms may develop. These include:
- passing large amounts of urine
- feeling thirsty with a dry mouth
- felling tired
- Losing appetite
- Losing weight
- Vomiting or abdominal pain
- Infections, e.g. thrush
- ketones appear in the urine
- glucose is present in the urine
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
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.