How to Fast Before a Blood Test
Many times your doctor will order a blood test and it will require that you fast before taking it. These could be, for example, a fasting glucose test to determine if you are a diabetic or it could be a test to measure cholesterol level. Eating or drinking can change the results of these tests and produce false positive or negative results. The amount of time you have to fast varies as does what you are not allowed to have, depending on the reason for the fast.
Calculate the time the fast begins. If the test is at 6 a.m. and you have to fast for six hours, stop eating at midnight.
Stop eating at the start time of your fast. This means do not eat anything, not even Jello.
Stop drinking anything at the start time of the fast. The sugar you add to your coffee, or the just sweetness of the milk can change the results.
Start drinking water if you are thirsty, unless your doctor has instructed otherwise.
Suck on an ice cube if you have been instructed not to drink water. This wets your mouth but does not break your fast. as long as you don’t swallow the melted ice cube water.