Can you use melatonin to help your child sleep? If yes, then what dose for a 6 year old?

Usual starting... ...Dose would be 1 to 3 milligrams at bedtime; it can be increased to at least 6 if not effective at lower dosages.
Yes & no. Melatonin has not been well studied in children and there are no established guidelines on proper dosing. Many practitioners consider it relatively safe. Using the lowest available dose is prudent. Studies in adults show persistence of grogginess at higher doses.