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A blood glucose test measures the amount of a type of sugar, called glucose, in your blood. Glucose comes from carbohydrate foods. It is the main source of energy used by the body. Insulin is a hormone that helps your body's cells use the glucose. Insulin is produced in the pancreas and released into the blood when the amount of glucose in the blood rises.
Normally, your blood glucose levels increase slightly after you eat. This increase causes your pancreas to release insulin so that your blood glucose levels do not get too high. Blood glucose levels that remain high over time can damage your eyes, kidneys, nerves, and blood vessels.
There are several different types of blood glucose tests.
Blood glucose tests are done to:
For a fasting blood sugar test, do not eat or drink anything other than water for at least 8 hours before the blood sample is taken.
If you have diabetes, you may be asked to wait until you have had your blood tested before you take your morning dose of insulin or diabetes medicine.
No special preparation is needed before having a random blood sugar test.
A health professional uses a needle to take a blood sample, usually from an arm.
You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of having a problem from this test. A small bruise may form at the site.
Results are often ready in 1 to 2 hours. Glucose levels in a blood sample taken from your vein (called a blood plasma value) may differ a little from glucose levels checked with a finger stick.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
You may have diabetes. To make a diagnosis of type 2 diabetes, your doctor will use the Diabetes Canada criteria.
Other conditions that can cause high blood glucose levels include:
A fasting glucose level below 2.2 mmol/L in women or below 2.8 mmol/L in men that is accompanied by symptoms of hypoglycemia may mean you have an insulinoma, a tumour that produces abnormally high amounts of insulin.
Low glucose levels also may be caused by:
Adaptation Date: 2/24/2022
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
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