Description of the test

Blood glucose testing allows people with diabetes to measure their blood glucose (sugar) levels at various times throughout the day to make sure it is within their target range.

Blood glucose testing is done using a blood glucose meter, which is a small portable machine that can be used at home or taken with you wherever you go. Testing strips are inserted into the meter, and the strips draw up a sample of blood into a test chamber within the meter. A chemical reaction occurs, resulting in a current that is measured by the meter to give you a reading of your blood glucose level. The level is given as a number and is measured in mmol/L (Canadian units).

The test also involves lancets (small needles used to prick the skin) and a lancet device that holds the lancet.

How often should the test be performed?

The frequency of testing depends on the type of diabetes you have and the type of medication therapy you are on:

  • People with type 1 or type 2 diabetes who use insulin more than once a day are recommended to test their blood glucose at least 3 times per day.
  • People with type 2 diabetes who are using insulin once a day should test their blood glucose once a day.
  • People with type 2 diabetes who are not using insulin should speak to their physician or primary health care provider about how often they should test. Usually, but not always, these people need to test less often.

Regardless of how often you test, it is important that you try to test at different times each day and do tests both before and after meals in order to get a complete picture of your blood glucose levels.

Why is this test performed?

It is important for people with diabetes to monitor their blood glucose regularly so that they can make sure their levels are within a safe range. Knowing your blood glucose levels can help you prevent or respond to emergency situations such as hypoglycemia (low blood glucose), which can cause shakiness, dizziness, and in extreme circumstances, even unconsciousness and death.

If you discover you have hypoglycemia, you can eat or drink something that will give you an immediate source of glucose. The results of testing your blood sugars can also be used to determine how much insulin you need before each meal, and if you require more or less insulin during exercise, times of stress, or illness.

Keeping your blood sugars under good control will reduce your risk of developing complications related to diabetes. If you find that your levels are consistently high, you should talk to your physician or primary health care provider, as you may require a change in medication or in diet and lifestyle.

Are there any risks and precautions?

There aren't many risks to be worried about regarding blood glucose testing. You should always wash your hands with soap and water before pricking your skin to avoid infection. You can also prevent infection by never using a lancet more than once. To avoid getting hard spots on your fingertips from frequent testing, try to use a different finger or different pricking site each time. The prick may hurt a little but you can minimize this by pricking the side of your finger, not the tip.

What happens during the test?

Be sure to wash your hands with soap and water and dry them before the test. If the test strips come in a bottle, remove one and then put the lid back on. If the strips are stored in your meter, read the instructions on how to release one strip. Prepare the blood glucose meter with the test strip according to the instructions.

Use the lancet device to prick the side of your fingertip with a lancet. Place a drop of blood onto the correct part of the test strip. The strip will draw up the blood into the meter. You only need a small amount of blood. Check the instructions to determine how much you will need for your specific meter. If you need more blood after pricking, use a finger from your other hand to apply slight pressure in an upwards motion toward the testing site (towards the tip of the finger) to release more blood.

There are also meters available that let you obtain a blood sample from areas other than the fingertip, such as the forearm, palm, or thigh. The accuracy of results taken from these sites may vary, with fingertip samples being the most accurate during periods in which blood glucose rapidly changes (e.g., after meals or during exercise). Blood samples that are taken from the palm (near the base of the thumb) are most closely correlated with those from the fingertip.

When finished, use a clean cotton ball to apply pressure to the testing site for a few moments until the bleeding stops. Most meters will give you a digital reading of your blood glucose level within seconds. Many will store your readings or let you download them to a computer. If not, be sure to record your results so you can discuss them with your health care provider.

How should I prepare for this test?

The only thing you need to do before the test is make sure that you wash your hands with soap and water and dry them thoroughly. You can also clean the test site with alcohol.

What can I expect after the test?

You can return to your normal activities immediately after the test. If your blood glucose reading is not within your expected range, then a change will be required. This could include changing your medications or diet. Talk to your health care provider about what to do when your blood glucose readings are above or below what you expect.


A blood glucose meter provides blood glucose test results immediately.

In general, a fasting blood glucose reading (taken before breakfast) should be between 4.0 mmol/L to 7.0 mmol/L. A blood glucose reading 2 hours after a meal should be between 5.0 mmol/L to 10.0 mmol/L. You should discuss your target blood glucose range with your health care provider. Depending on your situation, your health care provider may set different targets for you. Your physician or primary health care provider will also tell you what to do when your reading is not within your target range.