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Pathology and Laboratory Medicine
Specimen Collection Guidelines

​Fasting blood test guidelines

Fasting means you should not have anything to eat or drink for a minimum of 10 hours to a maximum of 14 hours before you go to the laboratory.



​May I drink water?​Yes, small amounts.
​Should I take my medications?​Yes, unless your doctor tells you not to.
​May I drink juice?​No.
​May I drink coffee or tea?​No, not even black without sugar.
​May I chew gum?​No, sorry, not even sugarless.
​During a tolerance test, may I smoke or exercise?​No, smoking or exercising can influence the tolerance test results.
​What time should I come to the lab?​Most people find it convenient to stop eating and drinking after
8 pm and to arrive at the laboratory early the next morning.
​May I brush my teeth?​Yes, brushing your teeth is permitted unless otherwise indicated by your physician, assuming you do not use large amounts of toothpaste and swallow the lather.
​May I take high dose vitamins and Biotin supplements?​No, high dose vitamins, supplements and biotin preparations interfere with common lab tests (such as thyroid tests). These should be avoided for 48 hours prior to lab testing.

Last Modified: Friday, June 1, 2018 |
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