I'm going today for a complete blood series, which I have done as part of an annual checkup. They always tell me to fast for 14 hours and drink nothing but water if necessary. Right now, I'm starving!!
I think for glucose testing, it's 8 hours of fasting and drinking only water, but I've never had just that test done.
To give you a different answer...12 hours is the norm in the UK. I know this because only yesterday my doctor has referred me for fasting blood tests, and it says clearly on the forms to fast for 12 hours.
To be honest I don't think it should matter that much between 8 - 14 hours as I would think your blood sugar level would stabilise after that amount of time. My understanding is that it goes up after eating, then back down to a 'normal' level once your body has digested the food.
I know that sometimes doctors check cholesterol as well as glucose at the same time, and that you have to fast longer for the cholesterol. My blood glucose levels (using my home meter) vary from outside of normal in the morning at 8 hours but comes down to almost normal at 12 to 13. Are you having a cholesterol check as well as your glucose? It all gets so confusing! But, then I guess if it did make a major differance, they wouldn't do the tests together. Did I just answer my own question?
The usual answer I hear is at least 10 hours. Based on the variety of answers I am hearing from the group ranging anywhere from 8-12 hours, 10 sounds reasonable in a pinch. Apparantly, every Doctor has his/her preference. I am told I can have black coffee with a sugar substitute but no cream or creamer. However, I hate black coffee so I stick to good ole' water. I know my answer didn't really clear things up but hopefully you will at least settle on a number so you can get some sleep.
If you were going just for a fasting glucose (blood) test, then 8 hours fasting is required. If your blood work includes testing for cholesterol (LDL, HDL, Triglycerides, et al), then 12 hour fasting is required.
Since I get those and some others done regularly every three months, I get the whole shebang on one reqisition, so I fast for 12 hours.
P.S. I asked last time why there was a difference and the nurse said the cholesterol test requires 12 hours fasting.