Fasting for Blood Work

If your doctor has prescribed blood work for you, you’ll need to know what blood test preparation is required. In some cases, you’ll have to do fasting for blood work. This article explains the fasting blood work rules and how to ensure your test results are accurate.

Why Am I Fasting Before a Blood Test?

Fasting before blood work isn’t always required. However, when your doctor says that it’s necessary, it’s important that you refrain from consuming anything other than water for the period specified. Eating or drinking can skew the results of your test, which can subsequently affect your diagnosis and/or treatment, if any. The two most common types of tests where fasting for blood work is required are glucose tests (which measure blood sugar) and lipid tests (which measure the amount of triglycerides and cholesterol in your blood).

How Long to Fast Before a Blood Test

How long should you fast before a blood test? That varies based on the type of test. Your doctor will let you know how many hours to fast before a blood test; typically, 8-12 hours. Fasting blood tests are generally scheduled early in the morning, which means that much of your caloric restriction occurs while you’re sleeping. In most cases, you can eat as soon as the testing is over. Consequently, you may want to bring food with you to your appointment if you anticipate being extremely hungry following the test.

What Can I Eat & Drink While Fasting Before a Blood Test?

A common question from patients is, “Can you drink coffee before a blood test?”. The answer—unless your doctor specifically tells you otherwise—is “no.” Some will also ask, “Can you drink water before a fasting blood test?”. Here, the answer generally is “yes.”

Other activities your doctor will likely have you refrain from include chewing gum, smoking and exercising. All can accelerate your digestion, which can adversely affect your results.

Important note: You should continue to take your prescribed medication while fasting unless your doctor specifically directs you not to.

Learn More About Fasting & Blood Work from Baptist Health

Learn more about fasting for blood work and the different types of blood tests with Baptist Health. If you feel you need blood work done, please schedule an appointment with Baptist Health today.

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