Can You Eat Before a Blood Test?

Blood tests are highly sensitive tests that you doctor can order for a variety of reasons. To ensure accuracy, some blood tests require that you quick before testing. Prior to having a blood test, your doctor will supply you with particular instructions to follow.

Blood Tests That Require Fasting

Blood tests used to inspect your cholesterol, glucose or triglyceride levels, or amounts of vitamins or minerals in your blood, you will probably need to fast prior to the measurement, due to the fact that nutrients in food contribute to the quantities of these substances in your blood. A thorough metabolic panel, which tests for the presence of liver and kidney problems, in addition to diabetes, likewise requires fasting.

Blood Tests That Do Not Require Fasting

There are blood tests that do not need any unique preparation. For instance, you will not need to quick prior to undergoing a blood test that figures out if you are pregnant. Fasting is likewise not likely needed for a blood test that identifies your blood counts– such as a total blood count, or CBC. The number of blood cells in your body remains the same despite whether you eat anything.


If you are required to quick prior to your blood test, your doctor’s office will supply you with particular instructions. The majority of cholesterol and triglyceride blood tests need that you fast for 12 hours prior to your test. If you are having your glucose levels or vitamin levels checked, you will have to quickly for at least 8 hours prior to your test.

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Fasting Requirements

You are allowed to have water even when you quickly for a blood test. Depending upon the nature of your test, your doctor might likewise allow you to drink black coffee or tea prior to your test, otherwise you need to not take in any other type of liquid besides water. If you are needed to fast, you will not be permitted to have any food– this includes gum with sugar content. Talk to your doctor about taking medications prior to your blood test.


If you do eat when instructed to fast, it can considerably change the results of your blood test. For instance, you might have irregular test results when they might have been normal if you fasted. When asked if you have had anything to eat prior to having your blood test, be honest with the individual administering your test. Failure to be honest might result in your having to have a 2nd blood test.

Foods to Avoid Before Having a Blood Test

Fecal Occult Blood Test

A fecal occult blood test is used to measure blood in the feces for detection of colon and intestinal problems. Certain foods should be avoided several days prior to a fecal occult blood test, according to These include red meat, which can turn your test favorable; foods such as radishes, turnips, cabbage and cauliflower which contain a chemical that can turn the test favorable; and citrus fruits or vitamin C supplements that can turn your test wrongly unfavorable.

Blood drop - test

Lipid Blood Tests

Prior to a lipid blood test, a 12-hour fast is advised, mentions the Cleveland Clinic. According to, this is because of that triglycerides are abnormally high after meals. Since LDL, or “bad cholesterol,” is computed using fasting triglyceride levels, eating prior to a lipid blood test might affect LDL cholesterol results.

Blood Sugar Test

Blood sugar tests are used to determine the quantity of digested carb present in the blood. An online resource of the National Institutes of Health, blood glucose tests are generally performed when a person is thought to be at risk for diabetes. For a fasting blood sugar test, it is advised that you not drink or eat anything 8 hours before the test, unless the blood test is being done arbitrarily, which would be defined by your doctor.

Total Blood Count

A complete blood count, or CBC, is used to determine such blood parts as hemoglobin, hematocrit, red blood cells and white blood cells. No fasting or avoidance of foods is necessary prior to this particular blood test.


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