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Blood Glucose: About This Test

What is it?

A blood glucose test measures the amount of a type of sugar, called glucose, in your blood. A few different types of blood glucose tests are used.

  • Fasting blood sugar (FBS) measures blood glucose after you have not eaten for at least 8 hours. It is often the first test done to check for prediabetes and diabetes.
  • Random blood sugar (RBS) measures blood glucose regardless of when you last ate.

Why is this test done?

Blood glucose tests are done to check for diabetes or to see how well treatment for diabetes is working.

How do you prepare for the test?

Fasting blood sugar (FBS)

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.

Random blood sugar (RBS)

No special preparation is needed before having a random blood sugar test.

How is the test done?

A health professional uses a needle to take a blood sample, usually from an arm.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

Go to https://www.healthwise.net/patientEd

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Care instructions adapted under license by your healthcare professional. If you have questions about a medical condition or this instruction, always ask your healthcare professional. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.