Insulin dose adjustment with food: glycaemic index (GI)
insulin dose pages from DAFNE
Why test glucose levels and adjust insulin dose?
Food good control insulin dose has to matches carbohydrate intake.
Starch and sugars (carbohydrates) are the foods that cause blood glucose
to rise, and these are the main foods that you need to consider when adjusting
quick-acting insulin dose.
Food contains a mixture of fat, protein, carbohydrate and fibre:
||meat, nuts, fish, cheese,
||butter, margarine, oil, cream, mayonnaise
||bread, rice, pasta, breakfast cereals, milk, fruit,
|carbohydrate with protein etc
||pulses (lentils/beans etc)
Fibre, fat, protein
Fibre (most vegetables) has no calories and so a negligible effect on blood
glucose. Fat and protein have a small effect, although this can be significant
on occasions (for instance if large amounts are eaten). We can ignore their
effect at this stage; it is covered in more detail on the DAFNE course, and
patients can work out the effect themselves by regular glucose testing.
Carbohydrate is the main food group that causes a rise in blood glucose,
and the does of insulin should match the amount of carbohydrate eaten. Unless
the insulin dose and blood insulin level dose match the blood glucose level,
the diabetes will not be controlled.
Foods that contain carbohydrates need to be matched accurately with quick-acting
insulin if you are to achieve good glucose control. You can eat as little
or as much carbohydrate as you want, as long as it is matched by quick-acting
insulin (although large amounts will increase weight!):
|food containing carbohydrate
||fruit & vegetables
- bread / chapattis / naan
- breakfast cereals
- biscuits / crackers
- pastry / scones
- cakes / teacakes
- yorkshire pudding
- crisps / waffles / chips
- fruit juice
- beans / pulses / lentils
The carbohydrate portion
Good diabetic control involves eating the amount of carbohydrate you would
like, and learning how to match this with an appropriate dose on insulin.
Carbohydrate portions (CPs) are a way of judging the amount of carbohydrate
One carbohydrate portions (CP) contains about 10g of carbohydrate.
- 10g carbohydrate portions = 1 CP
- 15g carbohydrate portions = 1.5 CP
- 20g carbohydrate portions = 2 CPs
By using the carbohydrate
portion list as here you will be able to add up the carbohydrate
value of the foods you would like to eat. You can then inject the right
amount of quick-acting insulin to match this. On the DAFNE training
program, you will begin to learn how many units of quick-acting insulin
you need for each 1 CP. Carbohydrate in both meals and snakes will need
An example of Carbohydrate counting (thanks to colleagues at Good Hope)
Meal plan for a type 1 patients with a ratio
- 1.2u : 10g at breakfast
- 0.8u : 10g at lunch
- 0.8u : 10g at evening meal
||food / drink
||CHO estimate (g)
- 2 x weetabix
- semiskimmed milk
- orange juice
- McDonalds Meal
- Big mac
- medium fires
- medium diet coke
- cicken curry
- white basmati rice
- apple juice
- 1 pear
- 2 rich tea biscuits
Different types of carbohydrate and their effect
on glucose levels
Sometimes glucose levels rise or lower unpredictably. It is not just the
amount of carbohydrate, but also the type that affects blood glucose levels.
Different starches are absorbed at different rates.
- For example, pure fruit juice (which contains sugar) acts as quickly
as Coco-Cola. However, whole pieces of fruit are digested more slowly.
- Some foods such as beans and lentils (these also contain protein) and
sweet corn cause very little rise in blood glucose, because they are slowly
- Mashed potato causes are far quicker rise than potato salad, because
mashed potato is more easily digested.
- Milk and yogurt contain a sugar called lactose that is digested very
slowly, so these cause a slower rise than the same amount of glucose in
- Foods that contain a mixture of fat and sugar are digested relatively
slowly because the fat slows down stomach emptying. Therefore, foods such
as chocolate and cake do not raise glucose levels very quickly.
You need to experiment with different foods to see how they affect you.
Blood glucose monitoring is the main way to find this out.
Glycaemic index (GI): how different foods affect blood
Food with a high glycaemic index GI (red) cause
a dramatic rise in blood glucose. Lower
glycaemic foods are healthier (green)
The speed of glucose rises and falls after eating a particular food is known
as the 'glycaemic index' of that food. Many foods have been tested, although
sometimes values change from day to day in the same person...so glycaemic
index is only a rough guide.
A carbohydrate that causes a fast rise and fall in blood glucose (i.e. quickly
absorbed) has a high glycaemic index; one that is absorbed more slowly has
a low glycaemic index. But as the speed of absorption is affected by other
foods eaten at the same time, the glycaemic index of carbohydrates becomes
important mainly if a single carbohydrate type is eaten in a large amount
or on its own.
Low glycaemic index (GI) foods assist diabetic control, high GI foods make good control difficult to achieve. High
High glycaemic foods
high glycaemic index
- Jellied sweets
- Boiled sweets
- Dextrose tablets
- Fruit juice
High glycaemic index foods (rapid-acting carbohydrate) are
good for treating hypoglycaemia.
Generally high glycaemic foods cause such high glucose spikes, even with
the 'correct' dose of insulin These the high levels are dangerous in the
long term, and contriubte to diabetic complications, so these food are best
avoided as part of the day to day diet..
Low glycaemic foods
|low glycaemic index foods
- lentils, beans,
- pulses of all types
Low glycaemic index foods are absorbed very slowly and
if you inject insulin to match carbohydrate you may find the insulin works
too quickly. Your blood glucose levels could fall before the carbohydrate
is absorbed. It is therefore best to ignore their carbohydrate content and
not give any insulin, or if eating large quantities of these foods, give
less insulin that would be anticipated from their carbohydrate content.
All other carbohydrate foods can be matched with Quick-Acting insulin, e.g.
chocolate, bread, milk, fruit, cereal.
How can I prevent weight gain?
Foods that contain fat provide many more calories than carbohydrates. For
example, one potato contains 70Kcal but a portion of chips contains 200Kcal.
Alcohol also provides many carbohydrates. See A dietician can provide individual advice, but healthy eating and physical
activity help you to lose weight.
Sweeteners and sugar substitutes
Many foods contain sugar, sugar substitutes, or sweeteners, and each has
a different effect on weight and blood glucose.
This causes blood glucose to rise, and contains calories. If eaten on
its own, it can lead to erratic blood glucose readings. If the sugar is
contained in a recipe then its effect on blood glucose is slowed down.
All sugar needs to be covered with quick-acting insulin.
Sugar substitutes (sorbitol, fructose, maltitol, and isomalt)
This do not cause rise in blood glucose levels and so do not need insulin.
For this reason they are used in many 'diabetic' products. Unfortunately,
they have a laxative effect, and are very expensive. Although they are
sugar free, they still contain calories, and can produce gain in weight.
These products are not recommend....we recommend you use ordinary products
(e.g. chocolates) and inject an appropriate amount of quick-acting insulin.
Arificial sweeteners (aspartamine, Sucralose, Saccharin)
These contain no calories and should have no effect on blood glucose.
They are found in soft drinks. Unfortunately new evidence suggests they
do not stop people being 'hungry' so they may end up having more calories
from other sources.