If you have taken more melatonin than it said on the label, you must go somewhere safe with someone who can watch over you while you sleep off the effects. You should also let your doctor know what has happened.
Rarely, melatonin can cause serious side effects, such as allergic reactions (difficulty breathing, swelling of your face or throat, itching skin lumps). If you get these or other serious symptoms, then you must go to a hospital straight away, taking your medicine with you.
You might feel sleepy in the first few days after taking melatonin - this is normal. Do not drive a car, ride a bike or operate machines until you see how this affects you.
Use good contraception while you are taking melatonin. We do not know whether taking melatonin while pregnant can affect the developing baby. Talk to your doctor or midwife about this and get their help if you want to get pregnant or think you might be pregnant.