I use it, and it works great! I've had major insomnia since I started dialysis, and a friend suggested I try melatonin, and it worked way better then I expected. I've been using it for about a year now and I've had very few nights where I've had trouble sleeping.
http://www.melatoninfaq.com/I'd check with my doctor first. There is some caution about use by people with kidney disease among others and also about potential interaction with prescription drugs such as BP meds. I do take some supplements but only after consultation with a conservative naturopath and my neph.