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 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 is the result.

With type 1 diabetes, the pancreas can no longer produce insulin. Those with 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.

With type 2 diabetes, the pancreas is still able to produce some insulin. Beginning stages of type 2 diabetes can often be treated with changes in eating habits, regular physical activity and/or pills. All of these treatments allow the body to more effectively use the insulin being produced.

The longer someone has type 2 diabetes, the less ability the pancreas has to produce 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 medication. As time goes on, injections may also be needed throughout the day.

Advances in diabetes treatment have given doctors many more options to help those with diabetes have long, healthy lives. New types of insulin and new ways of using it are helping people with diabetes to keep blood glucose under control.

Types of insulin

Different types of insulin affect the body in different ways. Each insulin has:

an onset (amount of time it takes to start working)
a peak (when it is most effective)
a duration (how long it works).

The insulin available in Canada today comes in four basic types: rapid, short, intermediate and long acting.

Rapid acting insulin begins to work very quickly (immediately to 15 minutes). It reaches maximum effect in 60 to 90 minutes but maintains a minimal effect for about four to five hours. Since it has such a fast action, 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, reaching 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 resuspend the insulin before injecting. (See mixing instructions in Simple steps for injection)

Long acting insulin begins to work in 90 minutes. It has a similar effect the whole time it is working, which 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 also needs to be gently shaken to resuspend the insulin before injection.

Some people mix two types of insulin together in a syringe before injection. Only a few can be mixed together safely.

If you would like more information on mixing insulins, talk to your doctor, diabetes educator or pharmacist.

Injecting 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 and 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.

Simple steps for injection

Wash your hands with warm water and soap.
Gently shake cloudy insulin, such as NPH or premixes, to resuspend the insulin before injection. Roll vials or penfills between the hands and turn from end to end at least 20 times to get an even mixture. It is important not to shake the vial or penfill too hard as this can damage the insulin.
If you use an insulin pen, dial up two units of insulin and shoot it into the air. This removes any air from the penfill and checks that your pen is working. Next, dial up the dose that you need.
If using a syringe, first inject the same amount of air as your insulin dose into the vial while it is right side up. With the syringe still in the vial, turn the bottle upside down and draw up about five units of insulin. Push this insulin back into the bottle to get rid of any small air bubbles. You must do this once or twice, until you can see that there are no bubbles. Next, draw your insulin dose into the syringe.
Pinch a fold of skin and insert the needle straight in (at a 90 degree angle). If you are using a five or six millimetre needle, you may not need to pinch. Inject the insulin.
Keep the needle in the skin for five seconds before removing.

Where to inject insulin

Four different areas on the body are good places to inject insulin:

the back of the upper arms
the abdomen
the top and outer thighs
the buttocks.

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.

The goal of injecting rapid or short acting insulin before meals is to allow it to be absorbed quickly to work with the food being eaten. The abdomen is the best area to inject rapid or short acting insulin.

Intermediate or slow acting insulin should be absorbed more slowly, so injections into the arms, thighs, or buttocks work well for these insulins. Choose the same area (but not the same spot) to inject insulin at the same time each day, so the effect will be the same every day.

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 can affect how insulin injections affect you.

If you plan to exercise after an injection, take care to 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, avoid massaging the area after an injection.

Rotating injections

Although it is important to use the same area to inject insulin at the same time each day, you must choose a different spot 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 the proper absorption of insulin.

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.

Storing insulin

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.

Storage tips

Levemir® insulin is good for 42 days once opened. All other insulins are good for one month after opening. Open insulin should be kept at room temperature. Injections will be more painful if insulin is cold.
Store extra insulin in the refrigerator. Kept this way, unopened insulin can be used until the expiry date. Do not use insulin past its expiry date.
Insulin that has been frozen, heated, or exposed to direct sunlight should be discarded.
Clear insulin that has particles in it, or cloudy insulin that does not mix properly, may have been damaged. Do not use it.
Do not store the insulin pen(s) you are currently using in the refrigerator.

Checking blood glucose

Most people using insulin check their blood glucose before meals and at bedtime. This information allows them to know how much insulin to take with each meal. They can also confirm that blood glucose is not too low before going to sleep.

Those on rapid acting insulin may also check blood glucose two hours after a meal to make certain they took the right amount.

It is also important for people who use insulin to check anytime they suspect their blood glucose levels may be low. Ask your diabetes educator, doctor or pharmacist about the best times to check your blood glucose.

Hypoglycemia (low blood glucose)

A blood glucose level below 4.0 mmol/L is called hypoglycemia. For a person using insulin, common causes of hypoglycemia are:

increased physical activity
taking too much insulin
drinking alcohol without eating
missed or delayed meals or snacks
eating too little food.

If your blood glucose is low, you may feel weak, hungry or nauseous. You may also experience clumsiness, trembling, confusion, tingling lips, or sweating. If you think you are experiencing hypoglycemia, do the following.

Check your blood glucose. If this is not possible, treat yourself anyway.
Eat or drink 15 grams of fast-acting carbohydrate. For instance, use:

three BD Glucose®, or five Dextrosol®, or four Dex4® tablets
¾ cup (175 mL) of orange juice or regular soft drink
3 teaspoons (15 mL) of honey.

Recheck your blood glucose after 15 minutes. If it is still below 4.0 mmol/L, treat again with another 15 grams of fast-acting carbohydrate.
Once your blood glucose is above 4.0 mmol/L, go ahead with your normal meal or snack. If your next meal is more than an hour away, eat a snack. Include 15 grams of carbohydrate and a protein source: for instance, six crackers with peanut butter or cheese, or a half-sandwich.

If you have any questions about how to recognize, treat or prevent low blood glucose, talk to your diabetes educator, doctor or pharmacist.

Since insulin was discovered by Dr. Banting in Toronto in 1921, it has been saving and improving the lives of people with diabetes. Advances since then have made insulin more effective, safer and easier to use. Without insulin, the body cannot create the energy required to survive. Insulin is essential for life, and with education and training, anyone with diabetes can safely use it.

Type of insulin	onset of action 1	Peak of action 1	Duration of action 1
Rapid acting Humalog® (lispro) NovoRapid® (aspart)	5 to 15 minutes	60 to 90 minutes	4 to 5 hours
Short acting Humulin® R (regular) Novolin® ge Toronto Hypurin® Regular (pork)	30 to 60 minutes	2-½ to 4 hours	5 to 8 hours
Intermediate acting Humulin® N Novolin® ge NPH Hypurin® NPH (pork)	1 to 3 hours	5 to 8 hours	Up to 18 hours
Long acting Lantus® (glargine) Levemir® (detemir)	90 minutes	No peak	Up to 24 hours
Premixed short acting and intermediate acting 2 Humulin® 30/70 Novolin® ge 30/70 Novolin® ge 40/60 Novolin® ge 50/50	30 to 60 minutes	2-½ to 4 hours and 5 to 8 hours	Up to 13 hours
Premixed rapid acting and intermediate acting Humalog® Mix 25 3 Humalog® Mix 50 NovoMix® 30 4	5 to 15 minutes	60 to 90 minutes and 5 to 8 hours	Up to 22 hours
Insulin action may vary in different people and at different times in the same person, so consider these times to be estimates only. 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. 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. 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 The Key to your body's energy management

The first time you heard about diabetes, you probably also heard about insulin. Your body makes this hormone in an organ called the pancreas. Insulin is your body’s energy manager.