can you drink coffee before a fasting blood test

You should generally avoid drinking coffee before a fasting blood test. Even black coffee, which contains no calories, can impact your test results due to its caffeine content and other compounds. Caffeine can raise blood glucose levels and affect cholesterol readings, which are commonly tested in fasting blood tests. Additionally, coffee is a diuretic, which can lead to dehydration, making it harder to draw blood and potentially affecting the accuracy of certain substances in your blood. Most healthcare providers recommend drinking only plain water during the fasting period (usually 8 to 12 hours before the test) to ensure accurate results. If you accidentally drink coffee before the test, inform your healthcare provider as they may need to take that into account or possibly reschedule the test. To play it safe, it is best to avoid coffee—including black coffee—before a fasting blood test unless your healthcare provider explicitly says otherwise.