minimum hours for fasting blood test
Fasting means that, from the night before the test, you must not eat anything and must. drink only water. Substances in tea, coffee or cola can affect some blood results, so even black coffee and sugar-. free (diet) drinks must be avoided. Likewise, chewing gum or smoking must be avoided on the. morning of the test. Fasting glucose Please fast for at least 8 hours. Oral glucose tolerance test Please fast for at least 8 hours. Note: this test takes a minimum of 2 hours.