When I was a teenager I would get menstrual cramps so painful that I could cry. I had to constantly take pain killers during each period.

I started taking 150mg of magnesium citrate each day a couple of years ago, and I have NEVER had a menstrual cramp since. My periods are painless. In my case it was just a magnesium deficiency!

Also when I was a teenager I would eat a lot of dairy and not a lot of magnesium containing foods so I think that contributed to it. My diet is much better now.