The body breaks down most of the food that is eaten into a type of sugar called glucose. Glucose travels to all the cells in the body through the blood. Insulin is necessary for glucose to leave the blood and enter the cells of the body, where it can be used to create energy. If the body is unable to make enough insulin to meet its needs, diabetes results.
With type 1 diabetes, the pancreas can no longer make insulin. People who have type 1 diabetes must inject insulin in order to survive. For good blood glucose control, injections are most commonly done three or four times daily. Using an insulin pump is another option.
With type 2 diabetes, the pancreas is still able to make some insulin. The beginning stages of type 2 diabetes can often be treated with changes in eating habits, regular physical activity and oral medications. All allow the body to use the insulin being made more effectively.
The longer someone has type 2 diabetes, the less ability the pancreas has to make insulin. Once medications no longer keep blood glucose at a healthy level, insulin must also be used. This may begin with an injection of intermediate or long-acting insulin at bedtime, along with oral medication. As time goes on, injections may be needed throughout the day.
Advances in diabetes treatment have given doctors many more options to allow those with diabetes to live long, healthy lives. New types of insulin and ways to use it help people with diabetes to keep blood glucose under control.
Different types of insulin affect the body in different ways. Each insulin has:
Insulin available in Canada today comes in four basic types: rapid, short, intermediate and long-acting.
Rapid-acting insulin begins to work very quickly (five to 15 minutes). It reaches peak effect in 60 to 90 minutes but maintains an effect for about four to five hours. Since it works so quickly, food must be eaten within 10 to 15 minutes of injection. For most people, the peak of rapid-acting insulin matches the highest rise in blood glucose after eating. For this reason, rapid-acting insulin can be very effective in lowering blood glucose after meals.
Short-acting insulin begins to work in 30 to 60 minutes, reaches peak effect in two and a half to four hours, and works for five to eight hours. This type should be injected 30 to 45 minutes before eating.
Intermediate-acting insulin begins to work in one to three hours, and reaches maximum effect in five to eight hours. It may last for up to 18 hours. It is a cloudy insulin and must be gently shaken to re-suspend the insulin before injecting. (See mixing instructions in Simple steps for injection sidebar.)
Long-acting insulin begins to work in 90 minutes. It has a similar effect the entire time it is working, and lasts up to 24 hours. Using long-acting insulin once or twice daily along with rapid-acting insulin at each meal gives results very close to the natural action of insulin in someone without diabetes.
Premixed insulin is a mixture of rapid or short-acting insulin mixed with intermediate-acting insulin. The onset, peak and duration of premixed insulin will differ depending on the insulin used in the mix. Premixed insulin must also be gently shaken to re-suspend the insulin before injection.
Some people mix two types of insulin together in a syringe before injection. Only a few insulins can be mixed together safely. If you would like more information on mixing insulins, talk to your doctor, diabetes educator or pharmacist.
Type of insulin
Onset of action 1
Peak of action 1
Duration of action 1
|5 to 15 minutes||60 to 90 minutes||4 to 5 hours|
Humulin® R (regular)
Novolin® ge Toronto
Hypurin® Regular (pork)
|30 to 60 minutes||2.5 to 4 hours||5 to 8 hours|
Novolin® ge NPH
Hypurin® NPH (pork)
|1 to 3 hours||5 to 8 hours||Up to 18 hours|
|90 minutes||No peak||Up to 24 hours|
|Premixed short acting
and intermediate acting 2
Novolin® ge 30/70
Novolin® ge 40/60
Novolin® ge 50/50
|30 to 60 minutes||2.5 to 4 hours
5 to 8 hours
|Up to 18 hours|
|Premixed rapid acting
and intermediate acting 3/4
Humalog® Mix 253
Humalog® Mix 503
|5 to 15 minutes||60 to 90 minutes
5 to 8 hours
|Up to 22 hours|
|1 Insulin action may vary in different people and at different times in the same person, so consider these times to be estimates only.
2 The first number is the percentage of short-acting insulin, the second the percentage of intermediate-acting (NPH) insulin. For instance, Humulin® 30/70 is 30 per cent regular insulin and 70 per cent NPH insulin.
3 Humalog® Mix 25 is a mixture of 25 per cent lispro insulin (rapid-acting insulin) and 75 per cent lispro protamine insulin (intermediate-acting insulin). Humalog® Mix 50 combines 50 per cent lispro insulin and 50 per cent lispro protamine insulin.
4 NovoMix® 30 is a mixture of 30 per cent aspart insulin (rapid-acting insulin) and 70 per cent aspart protamine insulin (intermediate-acting insulin).
Insulin injections have never been easier or less painful. Today’s thinner needles cause little pain when inserted through the skin. Insulin pens allow injections that are less noticeable in public. The pens are much easier to use than vials and syringes. If you currently use syringes for injection, talk to your pharmacist or diabetes educator about the benefits of using an insulin pen.
Four different areas on the body are good places to inject insulin:
These sites all have a layer of fat under the skin (called subcutaneous fat) that allows insulin to be correctly absorbed by the body.
Insulin will be absorbed at a different speed in each area. The abdomen is quickest to absorb insulin. Arms, thighs and buttocks all absorb it at a slower speed. Talk with your doctor or diabetes educator about whether you should avoid any of these four areas or if certain locations will work better for you.
Heat, strenuous activity and massage can all affect how quickly insulin is absorbed. Keep in mind that time in the sun, a warm bath or a hot tub influence how insulin injections affect you.
If you plan to exercise after an injection, avoid injecting those areas you will be using. For instance, do not inject into your arm if playing tennis is your next activity. Massaging the injection site increases the speed at which the insulin is absorbed. For this reason, do not massage the area after an injection.
Choose a different spot to inject insulin each time. If insulin is injected into the same spot over and over, fat can build up under the skin. This lump of fat, called lipohypertrophy, can interfere with insulin absorbing properly.
Each injection should be at about 2.5 centimetres (one inch, or the width of two fingers) away from the last. Scars, moles, or the navel (belly button) absorb insulin poorly. Stay at least five centimetres (two inches) away from these areas. If you have any questions about rotating injections, talk to your doctor, diabetes educator, or pharmacist.
Insulin is delicate. Special care must be taken to keep it safe. It should not be overheated, exposed to sunlight, frozen or roughly shaken. Insulin that is not handled correctly can lose its effectiveness. Damaged insulin may not be able to control your blood glucose levels.
Most people using rapid-acting insulin with each meal check their blood glucose before meals and at bedtime. This allows them to know how much insulin to take with each meal. They can also check that their blood glucose is not too low before going to sleep. Checking blood glucose two hours after a meal helps make certain they took the right amount of insulin.
Those who use only one daily injection of intermediate or long-acting insulin, or use premixed insulins, may need to check less often.
If you use insulin, it is important to check any time you suspect your blood glucose levels may be low. Ask your diabetes educator, doctor or pharmacist about the best times to check your blood glucose.
If you think you have hypoglycemia, do the following.
A blood glucose level below 4.0 mmol/L is called hypoglycemia. For a person using insulin, common causes of hypoglycemia are:
If your blood glucose is low, you may feel weak, hungry or nauseous. You may also experience clumsiness, trembling, confusion, tingling lips, or begin to sweat. See the Managing hypoglycemia sidebar at right for details on how to treat hypoglycemia.
Since insulin was discovered in Canada by doctors Banting and Best in 1921, it has been saving and improving the lives of people with diabetes. Further advances have made it more effective, safer and easier to use. Without insulin, the body cannot create the energy required to survive. Insulin is essential for life. With education and training, anyone with diabetes can use it safely.