Patient education: Blood glucose tests (The Basics)

What is a blood glucose test? — This test checks how much sugar is in the blood. "Blood glucose" is the medical term for blood sugar. Having the right amount of sugar in the blood is very important for the body to work the right way. Sugar gives cells energy to work.

If blood sugar gets too high or too low, it can cause serious health problems.

Why might I get a blood glucose test? — Your doctor might order a blood glucose test to:

●Check for high or low blood sugar levels

●See how well your pancreas is working

●Find out if you have diabetes

●Check for gestational diabetes (diabetes that starts during pregnancy)

How do I prepare for a blood glucose test? — How you prepare depends on which type of test you are having. They all involve having a small amount of blood taken from a vein in your arm (figure 1). The doctor might order a:

●Random blood glucose test – This can be done at any time. You do not need to do anything special to prepare for it.

●Fasting blood glucose test – This checks your blood sugar level when you have not had anything to eat or drink but water for 8 to 10 hours. Most of the time, this test is done in the early morning.

●Oral glucose tolerance test – This checks your blood sugar before and after you drink a special drink with a lot of sugar. It shows how well your body reacts to large amounts of sugar. Your doctor or nurse will tell you if you are able to eat and drink normally or if you need to fast (avoid eating or drinking) before your test.

A glucose tolerance test can take up to 3 hours. For this test, you will:

•Have a small amount of blood drawn from a vein

•Drink a special liquid with a specific amount of sugar in it. The liquid tastes sweet like a sugary soda. You need to drink the whole amount within a few minutes.

•Wait at the testing place, and have your blood drawn 1 or more times in the next few hours. After your last blood test, you can eat and drink normally.

What do my blood glucose test results mean? — Depending on when and why you got a blood glucose test, it might take a few hours to a day or 2 to get the results. Your doctor or nurse will contact you with the results when they are ready. Or if you use an online "patient portal," you might get an alert there when your results are ready. If it has been several days and you have not received your results, call your doctor's office.

If your blood glucose test shows any abnormal results, your doctor or nurse will talk to you about what to do next. They might need to do more tests to figure out what the problem is.

If you do have a health problem, your doctor will work with you to come up with a plan for treatment.

More on this topic

Patient education: Low blood sugar in people with diabetes (The Basics)
Patient education: Low blood sugar in people without diabetes (The Basics)
Patient education: Type 1 diabetes (The Basics)
Patient education: Type 2 diabetes (The Basics)
Patient education: Gestational diabetes (The Basics)

Patient education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)
Patient education: Type 1 diabetes: Overview (Beyond the Basics)
Patient education: Type 2 diabetes: Overview (Beyond the Basics)
Patient education: Gestational diabetes (Beyond the Basics)
Patient education: Glucose monitoring in diabetes (Beyond the Basics)