Why do you have to fast before a Blood Test?

The products from food digestion may pass on to the blood stream by having any food or beverages before a fasting blood test. The blood properties before and after consuming a meal differ, so one has to follow the fasting rules perfectly for having a successful fasting blood test. Food consumption affects glucose levels, lipid levels such as triglyceride, (LDL) and (HDL) and does not provide accurate results. Many of these also change from time to time. Obtaining exact results largely depends on the patient’s cooperation with the doctors and physicians and with it have appropriate medication.

Fasting For Blood Test

Some of the common tests that require fasting are:

• Cholesterol blood test
• Glucose blood test
• Vitamin blood test
• Triglyceride blood test

Fasting Blood Tests

Cholesterol Blood Test

American Heart Association recommends all people who are 20 years and above to have a cholesterol test every 5 years. The patient has to be on a fast for at least 12 hours to have this test. This test can be done at a laboratory or home using cholesterol monitoring device. With this test one can analyze lipoprotein panel profile of a person that details LDL or bad cholesterol, HDL or good cholesterol, total cholesterol and triglycerides. People with a total cholesterol of 200 mg/DL or more and good cholesterol of 40mg/DL or lower should have this test frequently until they get these in acceptable limits.

Glucose levels Blood Test

To check the glucose levels of the patient, fasting blood sugar test, postprandial glucose test, glucose tolerance test and random glucose test have to be done. This test is commonly used for testing diabetes or pre-diabetes. Doctors advise patients having diabetes to get this test done regularly. For fasting blood sugar test one should be on fast for 12 hours. A level of 70 to 100 mg/DL is normal anything more than that may need medical attention, as it may be pre-diabetes or diabetes.
 

Vitamin Blood Test

For vitamin tests, one needs fasting of around 8 hours to 12 hours. There are some things, which one has to avoid for having a successful blood test. Chewing gum with sugar and consuming any liquid other than water is an absolute no-no. One should also refrain from smoking prior to having a fasting blood test. Working out or exercises should also be avoided before a fasting blood test. For cholesterol tests, it is better if one can avoid consuming meat, eggs and other high fat foods over the week, though they do not drastically change the net result of the fasting blood test.