Most side effects of melatonin are mild. Common melatonin side effects include:
Headache.
Dizziness.
Nausea.
Drowsiness.
Timed-release melatonin can make you drowsy throughout the day, so use caution when driving or using heavy machinery. Children taking melatonin can have additional side effects. These include:
Increased bedwetting or urination at night.
Agitation or irritability.