how long do you have to before blood work
Report Abuse. 1  It depends on what the blood work is being drawn for. 2  Depending on the tests, he may need to fast for 12 hours before having the blood work done. 3  This depends on the lab work.  i have had a known practitioner say 10 hours and yet another known practitioner say 12 hours.
Quick Answer. As a general rule, patients should avoid eating or drinking anything other than water during the 12 hours prior to any blood test. Blood tests specifically prohibiting alcohol consumption in the 24 hours prior to the administration include the triglyceride test and the gamma glutamyl transferase (GGT) test.