Importance of Fasting Before Blood Results

If you're wondering if fasting before blood tests is really important or not, you need to understand why you are being asked to fast. Not all blood tests require you to fast, but the ones that do make this a requirement do so for a reason.

If you are scheduled to have blood tests done and your doctor does not specify if you need to fast or not, you should find out what tests you will be having done and ask specifically if you will need to fast or not. Your doctor will probably give you a printed sheet of directions that will specify if you can eat or drink before the test, and at what time your fast will begin. Some blood tests do not require you to fast at all; if you are having one of these test, you can go ahead and even have a snack right before the test is performed, since this can keep you from feeling queasy. Some blood tests will require you to avoid certain foods, types of drinks or medications. It's important to ask your doctor for details so you will get accurate results.

There are two types of common blood tests that are significantly affected by fasting or not fasting. These are blood tests to determine lipids levels in the blood and blood sugar levels.

Your blood sugar levels and lipids levels vary throughout the day. These levels are directly tied to the food you eat and the beverages you drink. Every time you eat, your blood sugar level is affected, and your body responds by producing and releasing insulin to monitor your blood sugar level. Likewise your lipids level changes as you eat and drink. It is impossible to determine a baseline blood sugar level or lipids level without measuring these levels after a period of fasting.

Here's an example of why you need to stick to the fasting rules before you go for a blood test. If you are getting your baseline blood sugar level tested to determine if you have diabetes, but you sneak an English muffin in for breakfast before the test, your blood sugar level will register as too high for a fasting level, and you will be diagnosed as a diabetic. Likewise, fasting allows your blood lipids level to settle in to a measurable and comparable level, and you will get an inaccurate report if you ate in the hours prior to the test.

Be sure to ask your doctor for specifics about fasting requirements. If you can't stick to the requirements and you cheat that morning, confess and reschedule the blood test so you can get accurate measurements.

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