Gastric bypass 6 months ago. is 2500 mcg b12/daily too much? will my kidneys jus flush out the excess essentially wasting it?

Yes, you are wasting: Daily requirement of B12 is less than 3 microg , even with gastric by gastric bypass you produce intrinsic and can absorb it in the distal ileum , any excess beyond liver storage capacity will be eliminated by the body . Vegans also need supplementation . Speak to your doctor , if you want your B12 levels could be checked.