Like all medicines, melatonin can cause side effects, but most people will not have any side effects.
Common side effects
Melatonin does not have many common side effects but there are things you can do to help cope with them:
Feeling sleepy or tired in the daytime
Do not drive, cycle or use tools or machinery if you're feeling this way. Do not drink any alcohol as this will make you feel more tired.
If you're taking more than one 2mg tablet talk to your doctor to see if you can reduce your dose. If this does not help, talk to your doctor as melatonin may not be the right medicine for you.
Headache
Make sure you rest and drink plenty of fluids. Do not drink too much alcohol as it can make your headache worse, and it affects the way that melatonin works. Ask a pharmacist to recommend a painkiller.
Talk to a doctor if headaches last longer than a week or are severe.
Stomach ache
Try putting a heat pad or covered hot water bottle on your tummy. Talk to your doctor if the pain continues or is severe.
Feeling sick (nausea)
Take melatonin tablets or liquid after food. Stick to simple meals and do not eat rich or spicy food. It can help to eat and drink slowly and have smaller and more frequent meals.
Feeling dizzy
If taking melatonin makes you feel dizzy, stop what you're doing and sit or lie down until you feel better. Do not drive, cycle or use tools or machinery if you're feeling dizzy. Do not drink alcohol as it will make you feel worse.
Feeling irritable or restless
If this does not get better after a few days, stop taking the medicine and talk to your doctor.
Dry mouth
Chew sugar-free gum or suck sugar-free sweets.
Dry or itchy skin
Apply a moisturiser often. Try using an oil-free face moisturiser for sensitive skin.
If this does not get better after 1 week, stop taking the medicine and talk to your doctor.
Pains in your arms or legs
If this does not get better after a few days, stop taking the medicine and talk to your doctor.
Strange dreams or night sweats
If this does not get better after a few days, stop taking the medicine and talk to your doctor.
Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.
Serious side effects
Serious side effects are rare and happen to less than 1 in 1,000 people.
Speak to your doctor if you start feeling low or sad as this could be a sign of depression.
Call your doctor or call 111 now if you:
- get changes to your eyesight, such as blurred vision
- feel faint or pass out
- start feeling confused or dizzy, or things seem to be spinning around you (vertigo)
- have any bleeding that does not stop, unexplained bruising or blood in your urine
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to melatonin.
Immediate action required: Call 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Other side effects
These are not all the side effects of melatonin. For a full list, see the leaflet inside your medicine packet.
You can report any suspected side effect using the Yellow Card safety scheme.