Melatonin is one of those multi-purpose supplements that actually does a few good things for you, but by far it's best known and most-widely used as a sleep aid. That's one of melatonin's primary functions within the body; the pineal gland in our brain releases melatonin hormone to help regulate our sleep/wake cycle. But like most hormones, we release melatonin less efficiently as we age which is one reason why older folks so commonly have sleep difficulties. It's also one reason why folks over 40 so often get great results with melatonin supplements in terms of promoting better sleep, both in terms of falling asleep and staying asleep.Liquid melatonin supplements like this one from supplement powerhouse Natrol, are the fastest-acting type and may be a better choice for those using melatonin for the first time. Start with the recommended dose about 30-45 minutes before bed, some users need to take more or less to get the best results. Most people will get the best results somewhere between .5 and 5 mg.