May 14, 2021

Everything You Need to Know About Fasting for Blood Work Tests

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.

What Blood Tests Require Fasting

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 Should I Fast Before a Blood Test?

How long to fast before blood work varies based on the type of test. Your doctor will let you know how many hours to fast before a blood test. Typically, you fast between 8-12 hours. Fasting blood tests are generally scheduled early in the morning because much of your caloric restriction occurs while you’re sleeping.

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.”

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.

Can you drink water when fasting for a blood test?

Water is fine to drink, but food and other liquids need to be avoided.

How soon can I eat after a blood test?

As soon as your blood test is over, you can begin eating and drinking. You might want to consider bringing a snack with you to eat as soon as the test is complete.

I Accidentally Ate Before a Fasting Blood Test. What Do I Do?

If you accidentally ate before a fasting blood test, please let your healthcare provider know right away so that you don’t receive incorrectly interpreted results. In some cases, you may still be able to receive your test as scheduled, but in other cases, you may need to reschedule your test to a different day.

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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