Blood Glucose Test

Why is a blood glucose test recommended?

Your doctor may order a blood glucose test to determine if you have prediabetes, type 1 diabetes, type 2 diabetes or gestational diabetes. Diabetic patients are not able to produce enough insulin — the hormone that controls the amount of sugar in your blood. If left untreated, high blood sugar levels can cause severe organ damage.

Your doctor may also order a blood glucose test if he suspects you are hypoglycemic — your glucose levels are too low.

How is a blood glucose test performed?

A blood glucose test involves taking a sample of blood from your finger and analyzing it in the lab. In some patients, a larger sample of blood is taken via a vessel in the arm.

How to prepare for a blood glucose test?

A blood glucose test can be performed after not eating food for a certain amount of time (fasting) or non-fasting.  

If you are having a fasting blood glucose test, you should not eat or drink within eight hours of the test. 

If you are having a non-fasting blood glucose test, you can eat or drink up until the time you have the test.
Fasting blood glucose tests are more accurate than non-fasting blood glucose test. If you have abnormal results on a non-fasting test, your doctor may repeat the test as a fasting test.

What are healthy blood glucose levels?

A healthy blood glucose range on a fasting test is between 70 and 100 milligrams per deciliter (mg/dL). A healthy blood glucose level on a non-fasting blood glucose test is under 125 mg/dL.

What are unhealthy blood glucose levels?

An unhealthy blood glucose level on a fasting test is above 100 mg/dL. If you have a blood glucose level between 100 and 125 mg/dL, you may have prediabetes. If your blood glucose level is 126 mg/dL or higher, you may have diabetes.

An unhealthy blood glucose level on a non-fasting test is above 140 mg/dL. If you have a blood glucose level between 140 - 199 mg/dL, you may have prediabetes. If you have a blood glucose level above 200, you may have diabetes.

How often do I have to be monitored if I have high blood glucose levels?

If you have high blood glucose, your doctor will work with you to develop a plan outlining how often you should check your blood sugar. He or she will take into consideration what type of diabetes you have and your treatment plan. 

If you have type 1 diabetes, you may need to check your own blood sugar as many as 10 times a day, including before and after eating or drinking.

Patients with type 2 diabetes will need to check their blood sugar a few times a day as well. Timing may be dependent on the type and amount of insulin you have been prescribed daily.

Some type 1 diabetic patients opt to have a continuous glucose monitor that can continuously monitor glucose levels and alert you when your blood sugar gets too high or too low.

Risks of a blood glucose test

There are very few risks associated with a blood glucose test. Risks may include:

• Excessive bleeding
• Fainting or lightheadedness
• Infection at the site where blood was drawn
• Hematoma if blood pools under the skin