if you donate a kidney is it true that you have to quit drinking alcohol??

No. Depnding on how much you drink. The average person needs only one kidney - the other is more like a spare. Consider this when we are infants both kidenys operate at 100%. 100+100=200% - the body only needs 20% function to function properly. Granted you lose function every day - the kidneys are in essence a sponge and it can only filter so much, so many times before it can't mop up anymore.

I would think if you are about to be a donor, there should be more important considerations then whether you can continue to imbibe.

i would say not to drink since it is hard on your kidneys.
I have a family memeber born with only one kidney
they never knew it untill there 50s when they passed a kidney stone
so for him what you dont know wont hurt you much

I agree with Hope. I didn't know I only had one until I was 38. I drank during college but never in excess as I was a "lightweight" though my ease of intoxication can have been due to the 1 kidney.