how many hours are necessary for fasting for blood work?
<answer> 8 to 12 hours are necessary for fasting for blood test. <context> Usually, 6 hours is the minimum amount of time in which to perform any fasting test (at a hospital, anyway). But...the longer the better. usually blood tests are done in the morning in a fasting state meaning that you shouldn't eat anything 8-12 hours prior to the testing.