Hi all- I have a blood test scheduled for 9:30am Saturday morning and was wondering what an optimal amount of time to fast before the draw would be. I've heard 8 hours recommended for glucose testing and 12+ for lipid testing. I imagine that fasting for too long might cause my blood sugar to eventually rise above its baseline level and that there would also be a hormonal reaction to a long fast.
For what it's worth, I'm having the following tests done: comprehensive metabolic w/ eGFR (minerals and kidney/liver markers, I believe), lipids, CBC, C-reactive protein, TSH, free T4, free T3, free/total testosterone, D,25-OH.
Additionally, are there are any important considerations regarding what I eat for my last meal before the fast? Thanks in advance for any help!
What did your doctor say when he ordered the test? You could call the blood lab and ask, too. I've always done at least 12 hours, sometimes more.
As for what to eat, I'd stick with your normal diet. I wouldn't want to slant the numbers one way or the other since I'd like to have good info rather than good numbers.
Your physician or the laboratory physician should tell you how long to fast. The best laboratory values will depend on the protocol for processing each test -- for example, no food after midnight is a typical protocol for an 8 am test, but your doc may tell you to FINISH your final meal by 8pm, so that digestion is complete by midnight, for example.
It may also be that your water intake may be restricted, so be sure to ask. And no mouthwash, no gum, no breath mints.
No exercise either.
If you have been low carbing (less than 50g/day) you may need to up those levels at least 3 days before the test, else your fasting glucose may give you a false reading.
Here's a few more tests to consider
Good luck and report back to us on the results...squeeze the ball...say ouch!