Melatonin is the hormone that regulates our sleep-wake cycle. Melatonin is not a universal sleeping aid that works for everyone. It's usually a good idea to begin with a very modest dose of melatonin and observe how you react. It is possible that as little as 1-3 mg will suffice. If it doesn't seem to be doing anything for you, try another smaller dose until you find one that does help you sleep.