Question

how many vitamins can i use on one pokemon?

Answer 1

The MAXIMUM that you can use is: 51.
Vitamins give EVs, which a Pokemon can only have 510 of. Also, You cannot use more than 10 of 1 kind of Vitamin per stat. There are 6 Vitamins, meaning there could be 60 uses, but 510 is the maximum.
Meaning something like:
10 HP up+10 Carbos+10 Protein+10 Zinc+10 Calcium+1 Iron=51 Vitamins

But you cannot:
51 HP up
10 HP up+10 Carbos+10 Protein+10 Zinc+10 Calcium+10 Iron

Answer 2

You can only use 10 of each kind on one pokemon, and since, you can have a total of 510 total EVs on one pokemon(each drug gives 10 EVs), you could use 8 of each to come out with 480 EVs and put 3 more into different stats. Or 10 in 5 different stats and then add 1 to the last. However you're question isn't very specific... Hopefully this helps.

EDIT: and I was beaten to the punch, good answer Mew!

Comments

Drugs?

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Lol, haven't you seen the pokemon shoot em up?