Apparently it works as effectivley at lower doses.

Someone posted this a while back, and it goes into a lot of detail: https://www.lesswrong.com/posts/E4cKD9iTWHaE7f3AJ/melatonin-...

It's the correct dose. See https://slatestarcodex.com/2018/07/12/did-a-melatonin-patent... for the sad background.

TLDR: MIT did a study and patented Melatonin usage with reasonable dosages. Manufactures just increased the dose 10x to get around the patent. The patent is expired but the damage remains.

0.5mg of melatonin is a perfectly good dose. For many people, anything over 1mg means sleepiness on the next day. I suggest doing some research, including how to taper it down once you no longer feel it's right for you.