The FAA medical does not test for alcohol, but if you are hung over that can affect several other things:
- Blood Sugar (this is why you pee in a cup)
- Hearing/Vision may not be optimal
- And the biggy...heart rythym. A few irregularities on your EKG are usually normal, everybody has them daily or hourly. But since the FAA EKG only measures about 6 seconds, if an irregularity shows up they don't know if you are experiencing them daily, hourly, or every six seconds. Because of this uncertainty, you will have to spend thousands of dollars on special tests just to verify your cardiac health. You will not be grounded, but it's still an expensive PITA.
Caffeine is also likely to cause funny EKG results, so I schedule my medical first thing in the AM, skip the coffee, then hit starbucks on my way home.
Avoid these things:
1) Heavy booze several days prior (maybe one beer the night before)
2) Caffeine the day of
3) Strenuous exercise the day before
4) Massive dietary deviations the day before (don't eat 3 large garbage can pizzas for dinner)
5) Dehydration
6) Vitamins/supplements the day of.
If you are taking an airline employment physical, assume they test for everything, and clean up your act one week before. I don't know how serious they are about supplements, or if their tests can detect them...but they usually ask you about suplements.