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A 31-year-old male asked:

Is 35 hours before a blood test enough time for one to drink caffeine before a blood test? i dont want to mess up my results bc i drank caffeine.

3 doctor answers7 doctors weighed in
Dr. Hunter Handsfield
Infectious Disease 54 years experience
No problem: Caffeine has no effects on any blood tests. Drink as much coffee or other caffeine drinks as you like, right up until you are tested. It won't make any difference.
Dr. James Ferguson
Pediatrics 47 years experience
Depends on the test: Many tests are unaffected by intake coffee or meals. Some tests are based on comparing everyone who has fasted overnight, or a specified time frame. Since you did not mention the name of the test, it is hard to be specific. However, if the doc did not tell you to fast/avoid coffee I would not worry about such timing.
Dr. Gurmukh Singh
Pathology 50 years experience
A few tests: A few tests, especially for hormone levels maybe affected by caffeine intake. Your doctor should advise you about dietary restrictions for the test, Some tests require abstaining from aspirin or antacids. Even the tests that require fasting, an overnight fast of 12 hours is generally more than sufficient.
Last updated Apr 17, 2019

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