Q&A: What happens if you don’t fast before a blood test?

Data: 2020-12-03


What happens if you don’t fast before a blood test? Should you still do the test?


If you don’t fast before a test that requires it, the results may not be accurate. If you forget and eat or drink something, call your provider and ask if the test can still be done. Some tests can be analyzed with a notation that it isn’t fasting and results may vary. The main thing is to be honest. If you had a snack, a cup of coffee, or even a full breakfast, tell the technician when you have your blood drawn. They should make a note so that the results are reviewed with the food intake as a variable. And if fasting is an absolute must for meaningful results, they should stop and reschedule your blood draw. 
Deborah Weatherspoon, PhD, RN, CRNAAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.


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