It's technically possible to take too much magnesium, so I think the maximum dose recommended in a supplement is no more than 600 mg, but I think most people take less than this.

The other thing to be cautious about is there are several different forms of magnesium supplements, and many of them have a laxative effect. That's a good thing if you're trying to stay regular or are prone to constipation, but not so great if that's nothing something you're going for!

If it helps: My PCP told me 300 mg of magnesium is the dose that's been studied for muscle cramping.

Magnesium Glycinate does not have a laxative effect and is associated with reducing anxiety, helping with sleep, and relaxing the muscles. It's more expensive, but I figured I'd rather go with what was studied a little more. I take 150 mg magnesium glycinate and 300 mg of magnesium citrate (which can have a laxative at a high enough dose), but this is because I have slowed motility related to autonomic neuropathy.

I used this as a guide while I was deciding what to take and how much: https://www.healthline.com/nutrition/magnesium-dosage