Giving your child a tablet or capsule of melatonin before bedtime may help them sleep sooner and for longer. But there's a risk of side effects with this treatment.
The brand of melatonin that's available in the UK is only recommended for adults over the age of 55.  It's called Circadin. Doctors can prescribe melatonin to children, but they'll only tend to do this for serious sleep problems that can't be sorted out without drugs. Your child will probably need to see a specialist to get melatonin. 
Melatonin is a hormone. Hormones are chemicals your body makes naturally to control some of the things it does. For example, hormones can tell your body how to use energy, or when to go to sleep.
Melatonin is the hormone that controls your body clock. Normally, your brain produces melatonin during the night to help you sleep. Your body starts to make melatonin when it gets dark, and stops when it gets light. The melatonin that's sold as a treatment is a man-made version of this hormone.
We found one good-quality study (a randomised controlled trial), which looked at how well melatonin worked for children aged 6 to 12 years who had sleep problems. The children took melatonin before going to bed.  The study found that the children:
But the study also found that the children:
Another study found children slept better if they took 5 milligrams of melatonin before bedtime.  But this research may not be reliable because there were problems with how the study was done.
There hasn't been much research on the best dose of melatonin for children to take. For some children, high doses of melatonin don't help. Melatonin may be more helpful if your child has only a low dose.  
We also found two small studies that looked at children with epilepsy, and one study that looked at children with attention deficit hyperactivity disorder ( ADHD for short). Taking melatonin didn't make much difference to how well the children slept overall.   
We don't know how safe melatonin is for children, or how safe it is to take regularly for a long time. There hasn't been enough research to say.
The studies we looked at found that children did have some side effects. Some of the children who took melatonin felt cold or dizzy or they had a low mood. Some children also didn't feel hungry and had mild headaches.  
There's also some evidence that children may get epilepsy or worse fits if they take melatonin, but we don't know this for sure. In one study we looked at, one child had mild epilepsy after four months of taking melatonin.  But in another study, 4 in 6 children with epilepsy had more fits when they took melatonin.  And they got fits less often when they stopped taking the supplement.
Some studies also suggest melatonin could delay the start of puberty.