When is it ideal to feed my pokemon vitamins?

During which part of my training should I feed my pokemon vitamins? When is it most beneficial?

I've been doing some serious EV training and have heard some people say that it's best to feed them as early as possible or as late as possible. Does that mean I should feed them as soon as I hatch from an egg or at a certain level?

When I've done it from egg hatching, I see barely any gain to my stats. I know it raises the base stat but shouldn't I still see some gain to my stats at that time?

Solution 1:

You have to feed the Vitamins to your Pokemon early. EVs in a given stat can go up to 255, but Vitamins can only boost EVs up to 100, and the rest must be gained manually. For that reason, it's generally easiest to feed the Pokemon 10 of whatever vitamin you want and then train up the rest of the way.

It doesn't exactly affect the "base stat" as you suggest. Rather, the bonus stats from the EVs are prorated per level. If you would get an additional 100 stat points at level 100, then you'll only get an extra 1 per level. Since the cap of additional stat points you can gain through EVs in a single stat is 63, you'll see less than one stat point per level. At level 1, you won't see anything. As you level up an EV trained Pokemon, however, the bonus will become more significant.

Bottom line: Use 10 vitamins right away, but don't expect to see the results of it until you start gaining levels.