Fasting for a blood sugar test measures the glucose(sugar) in the blood accurately. It is a safe, simple and common way to diagnose prediabetes, diabetes or gestational diabetes (during pregnancy).
If your health care provider has asked you to do a fasting before a blood test, it means you shouldn’t eat or drink anything except water for several hours (8 – 12 hours) before the test because if you do so the foods and beverages are absorbed into your bloodstream. This could affect the results of certain types of blood tests.
Tests requiring fasting before a Blood Test
Usually, the fasting time has to begin overnight, only then these tests will be scheduled early in the morning. Also, ensure to avoid medicines, smoking and activities like exercises as it can also affect your results.
There are no complications in fasting for a blood sugar test. The most common types of blood tests that require fasting include:
Glucose tests are done Glucose tests to measure blood sugar and to diagnose diabetes. There is one type of glucose test which is the glucose tolerance test where you need to do fasting before a blood test at least for 8 hours before arriving at the lab or health care facility.
- You will have your blood tested
- You will be asked to intake a special liquid containing glucose
- Your blood will be re-tested possibly between 1 – 3 hours later
Lipid tests are done by fasting for a blood sugar test. This test is to measure a type of waxy fat found in the bloodstream (triglycerides) and cholesterol in your blood and every cell of your body. High levels of triglycerides or cholesterol is called LDL which can put you at risk for heart diseases.
What can you expect on the day of the Blood Sugar Test?
Fasting for a blood sugar test is often done with a common blood draw. Your health care provider will
1. Clean the area inside the elbow to kill germs
2. Tie a band around the upper arm to help your veins in the arm fill with blood
3. Insert a clean needle into your vein (which makes you feel like a brief pinch)
4. Draw blood into a vial attached to a needle and labeled with your personal information
5. Remove the band and needle later
6. Put a little pressure on the needle insertion site to stop bleeding
7. Place a bandage on the tested area
After the test procedure is done, your health care provider will send the blood sample to the lab for testing. Only in rare cases, the health care provider will be able to test your blood sugar with a prick on the finger instead of inserting a needle in the vein. Then he/she uses a blood glucose monitor and test strip to check your blood glucose level.
When can you expect the test results?
The results of fasting for a blood sugar test are usually available quickly within days or hours. The level of blood sugar will come back as a number at the time of results.
1. 99 mg/dL or lower : a normal fasting blood sugar level.
2. 100–125 mg/dL : Fasting for a blood sugar test in this range typically indicates,prediabetes which means the blood sugar levels are higher than normal but not so high enough to be classified as diabetes.
3. 126 mg/dL or above : indicates high blood sugar which can be the main sign of diabetes.
Your healthcare provider may repeat the test when you have a high fasting blood sugar level. If the fasting for a blood sugar test reveals that you have prediabetes, he/she will recommend you to repeat the fasting blood sugar test every year or two. The results obtained on fasting before a blood test will help you know whether you are progressing to Type 2 diabetes.
Read also What is PCV in Blood Test.