Miriam and I read and posted about
the same study. It was 5 mg of melatonin, 225 mg of magnesium, and 11 mg of zinc. It was a pretty small study, so until a larger one confirms, I would not say it's gospel.
As Karen says though, do absolutely NOT take anything without discussing it with your doctor first. Somebody else's meds and OTC meds can interfere with meds you are currently taking. They can be dangerous to you.
You can get addicted to melatonin too. Your body can stop making its own, making you dependent on the pill.
I take melatonin, also Ambien sometimes, but not regularly. First I make sure to go to bed and get up at the same time every day. If I need a little help I take something for a couple of days. Then I find I feel sleepy at the right time all by myself. I make sure all my docs know what the others prescribe and the OTC meds I take.