Insulin for Type 1 and Type 2 Diabetes

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Insulin for Type 1 and Type 2 Diabetes


The different types of insulin are categorized according to how fast they start to work (onset) and how long they continue to work (duration). The types now available include rapid-, short-, intermediate-, and long-acting insulin.


Generic NameBrand Name
insulin aspartNovoRapid
insulin glulisineApidra
insulin lisproHumalog


Generic NameBrand Name
insulin regularHumulin-R


Generic NameBrand Name
insulin NPHHumulin-N


Generic NameBrand Name
insulin detemirLevemir
insulin glargineLantus

There are premixed rapid- and intermediate-acting insulins, including:

  • 70% intermediate-acting (NPH) and 30% short-acting regular insulin, called Humulin 30/70 insulin.
  • 50% intermediate-acting (NPH) and 50% short-acting regular insulin, called Humalog Mix 50 insulin.
  • 75% intermediate-acting and 25% rapid-acting Humalog (lispro), called Humalog Mix 25 insulin.
  • 70% intermediate-acting and 30% rapid-acting NovoRapid (insulin aspart), called Novo Mix 30.


Injectable insulin is packaged in small glass vials (bottles) and cartridges that hold more than one dose and are sealed with rubber lids. The cartridges are used in pen-shaped devices called insulin pens.

How insulin is taken

Insulin usually is given as an injection into the tissues under the skin (subcutaneous). It can also be given through an insulin pump, an insulin pen, or jet injector, a device that sprays the medicine into the skin. Some insulins can be given through a vein (only in a hospital).

Research is ongoing to develop not only new forms of insulin but also insulin that can be taken in other ways, such as by mouth.

How It Works

Insulin lets sugar (glucose) in the blood enter cells, where it is used for energy. Without insulin, the blood sugar level rises above what is safe for the body.

Your body uses insulin in different ways. Sometimes you need insulin to work quickly to reduce blood sugar. Your body also needs insulin on a regular basis to keep your blood sugar within a target range.

  • Rapid-acting and short-acting insulins reduce blood sugar levels quickly and then wear off.
  • When you use long-acting insulin with rapid- or short-acting insulins, the long-acting insulin starts taking effect when rapid- or short-acting insulins begin to wear off. The long-acting insulin glargine (Lantus) starts to work within 1 to 2 hours after it is given and continues to work at the same rate for about 24 hours. Lantus cannot be mixed in the same syringe with other types of insulin.
  • Usually people who take insulin use a combination of a rapid- or short-acting and an intermediate- or long-acting insulin. This helps keep blood sugar levels within a range that is safe for the body throughout the day.

Why It Is Used

Insulin is used to treat:

  • People with type 1 diabetes.
  • People with type 2 diabetes whose pancreas produces little or no insulin or whose oral medicines do not control their blood sugar. These people may take insulin either by itself or along with oral medicine.
  • People with type 2 diabetes whose blood sugar levels are high because of a severe illness or major surgery. After blood sugar levels return to a target range, these people may be able to stop taking insulin.
  • Women with type 2 diabetes who are pregnant or breast-feeding who cannot keep their blood sugar levels within a target range with diet and exercise. Only one oral diabetes medicine (glyburide) has been studied for use during pregnancy. Until further research is done, the Canadian Association recommends that pregnant women and women who are breast-feeding not take oral diabetes medicines.1

How Well It Works

Insulin is effective in reducing blood sugar levels by helping sugar (glucose) enter the cells to be used for energy.

For people with type 1 diabetes

Results of the 10-year Diabetes Control and Complications Trial (DCCT) and the follow-up Epidemiology of Diabetes Interventions and Complications (EDIC) study showed that people with type 1 diabetes who kept their blood sugar levels within a target range had fewer incidences of eye, kidney, and nerve damage from diabetes than people who were on standard therapy. Tightly controlled therapy also lowered the risk of heart attacks and deaths from heart disease.2

Studies have shown that insulin glargine (Lantus) and insulin determir (Levemir) work as well as NPH insulin for controlling blood sugar in people who have type 1 diabetes. Lantus and Levemir cause fewer low blood sugar episodes than NPH, especially at night.3

Side Effects

The major side effect of insulin can be a dangerously low blood sugar level (severe hypoglycemia). A very low blood sugar level can develop within 10 to 15 minutes with rapid-acting insulins.

Insulin can contribute to weight gain, especially in people with type 2 diabetes who already are overweight.

Other possible side effects of long-term insulin use include the loss of fatty tissue (lipodystrophy) where the insulin is injected and, in rare cases, allergic reactions that include swelling, or edema.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

People with type 1 diabetes who tightly control their blood sugar levels using either multiple daily injections or the insulin pump have lower hemoglobin A1c levels and may reduce their risk for developing small blood vessel complications (eye and kidney disease) compared to people who take one or two injections every day.

The insulin pump provides a way to give insulin with less frequent injections and is as effective as multiple daily injections at keeping blood sugar levels within a target range.

The long-acting insulin glargine (Lantus) may help prevent some people from having frequent nighttime low blood sugar levels. It may also be helpful for people who have had difficulty keeping their blood sugar levels in their target range with intermediate-acting insulin.

Giving short-acting insulin at the evening meal and NPH at bedtime instead of giving them together at the evening meal may reduce the risk of nocturnal hypoglycemia and hypoglycemia unawareness.

What can affect insulin

Some factors that affect how fast and how well an insulin dose works are:

  • Where the dose is given. If you give insulin into your abdomen (especially above and to the side of your belly button), the medicine will get into your system more consistently from day to day. If the medicine is given into a muscle or a small blood vessel instead of fatty tissue, the medicine will get into your system faster.
  • How much insulin is given. Higher doses of insulin reduce the blood sugar level more than lower doses.
  • Whether you have exercised before or just after taking insulin. If you have just exercised the muscles in the area where you give your insulin injection, the medicine will get into your system faster.
  • If you apply heat to the area. The medicine will get into your system faster if you take a hot bath or shower, put on a heat pack, or massage the area where you have just given your insulin injection.
  • If you do not have enough fluid in your body (you are dehydrated), you will not have as much blood flow to your skin, so insulin will not be absorbed as well as it would be otherwise.

Things to do

  • Label each insulin bottle when it is used for the first time, and discard unused medicine after 30 days. A bottle of insulin may lose its ability to work well (potency) after 30 days of use.
  • Store insulin properly so that its effectiveness is protected.
  • When you buy insulin, check the generic or brand names to make sure you are buying the correct type. For example, if you have been using Humulin-R (insulin regular), make sure you buy Humulin-R instead of Humulin-N (insulin NPH).
  • Know when your prescribed types of insulin start working (onset), when they work most (peak), and how long they work (duration).
  • Know how to give an insulin injection.
    Click here to view an Actionset. Diabetes: Giving Yourself an Insulin Shot
    Click here to view an Actionset. Diabetes in Children: Giving Insulin Shots to a Child

Precautions to take with long-acting insulin

The long-acting insulin glargine (Lantus):

  • Should be used only if it is clear, colourless, and contains no particles.
  • Should not be given using a syringe that has been used to give another type of insulin.
  • Should not be mixed with any other type of insulin. People who cannot take multiple injections may not be able to take this medicine.
  • Should be clearly labelled so it is not confused with short-acting insulins, which also are clear.
  • Usually is injected as one dose at bedtime. But it can be taken in the morning, and it can be split into morning and evening doses.
  • May cause more discomfort at the injection site than other types of insulin because it is acidic.
  • Should not be used in an insulin pump.

Children with type 2 diabetes

Insulin may be given as a single nighttime dose or as several smaller doses throughout the day.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. Canadian Diabetes Association (2008). Clinical practice guidelines for the prevention and management of diabetes in Canada. Available online:
  2. Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study Research Group (2005). Intensive diabetes treatment and cardiovascular disease in patients with type 1 diabetes. New England Journal of Medicine, 353(25): 2634–2653.
  3. Bolli GB, et al. (2009). Comparison of a multiple daily insulin injection regimen (basal once-daily glargine plus mealtime lispro) and continuous subcutaneous insulin infusion (lispro) in type 1 diabetes. Diabetes Care, 32(7): 1170–1176.


By Healthwise Staff
Primary Medical Reviewer John Pope, MD - Pediatrics
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer David C.W. Lau, MD, PhD, FRCPC - Endocrinology
Last Revised January 13, 2011

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