Before You Come To The Laboratory

Blood tests help doctors check for certain health problems and find out how well your body is working. Doctors also use them to figure out how well treatments are working. You don't need to fast before all blood tests. Your doctor will tell you if you need to.These tests typically require fasting:

Fasting blood glucose measures the amount of glucose (sugar) in your blood to test for diabetes or prediabetes.

Typical fasting time: At least 8 hours

Lipid profile is used to check the level of cholesterol and other blood fats. High levels put you at risk for developing heart disease or having a stroke.

Typical fasting time: 9-12 hours

Basic or comprehensive metabolic panel is often part of a routine physical. The tests check your blood sugar, electrolyte and fluid balance, and kidney function. The comprehensive test checks your liver function, too.

Typical fasting time: 10-12 hours

Renal function panel is used to gauge the health of your kidneys and how well they're working.

Typical fasting time: 8-12 hours

Vitamin B12 test measures how much of the vitamin is in your blood. It can help diagnosis a specific type of anemia and other problems. Some medications can interfere with this test. Tell your doctor about all the drugs you take.

Typical fasting time: 6-8 hours

Iron tests are used to see if iron levels in your system are too low or too high.

Typical fasting time: 12 hours

Gamma-glutamyl transferase (GGT) shows the level of the GGT enzyme in your system. A high reading may indicate liver disease, bile duct problems, or alcohol abuse.
Your doctor may ask you to fast for at least 8 hours beforehand. You also may need to avoid alcohol and some prescription drugs the day before the test because they can affect GGT levels. Talk to your doctor before stopping any prescribed medicines.

It depends on the type of blood test you're having and what medication you take.
If you're not sure or you have any questions about your blood test, ask your healthcare professional for advice.
You should never stop taking prescribed medication unless advised to do so by your healthcare team.

As a general rule, patients should avoid eating or drinking anything other than water during the 12 hours prior to any blood test. Blood tests specifically prohibiting alcohol consumption in the 24 hours prior to the administration include the triglyceride test and the gamma glutamyl transferase (GGT) test.