Got a symptom but not sure what's causing it? Use our symptom checker to find out.

×
21st December, 20205 min read

How much melatonin should I take – and can I overdose?

Medical reviewer: Dr Ann Nainan
Author: Daniel Piggott
Last reviewed: 17/12/2020
Medically reviewed

All of Healthily's articles undergo medical safety checks to verify that the information is medically safe. View more details in our safety page, or read our editorial policy.

We all have times when we find it more difficult to sleep. It could be because of jet lag, which is when your body struggles to adjust to a new time zone after a long flight. Or if you’re a shift worker, you may find that working at night makes it hard for you to sleep during the day.

Worries, anxiety and mental health problems can also cause an inability to sleep (insomnia). Children with certain conditions, such as ADHD, may also get insomnia.

You may have heard that melatonin can help you get a better night’s sleep. But how much should you take? Read on to find out what melatonin is and how it works, how to take it safely, and if it’s possible to overdose.

What is melatonin and why would I take it?

Melatonin is a hormone that our body makes when it gets dark, to let our brain know it’s time to sleep. When it’s light, our body makes less melatonin, which helps us to wake up. So, our internal ‘body clock’ (known as our circadian rhythm) is partly controlled by the levels of melatonin in our body.

Because melatonin helps with our patterns of sleeping and waking, man-made melatonin supplements can help people who are having trouble sleeping in the short term.

How much melatonin should I take?

The right dose of melatonin mainly depends on which type of sleep problem it is taken for. But it can also be influenced by your age, weight, and whether you take other medications.

Here are some recommended doses:

  • adults with jet lag – 3mg once a day (increased to 6mg if needed), for up to 5 days. To be taken between 8pm and 4am, with the first dose taken at normal bedtime after arrival at destination
  • adults with insomnia – 2mg, once a day, for up to 13 weeks. To be taken 1 to 2 hours before bed (usually only prescribed for adults aged 55 or over)
  • children aged 6 to 14 years with ADHD – unlicensed 3 to 6mg, once a day, for 10 days to 4 weeks. To be taken at bedtime (usually under the supervision of a specialist)

Always speak to a doctor or pharmacist before taking a new supplement or medication, to check that it’s suitable for you. And remember to read any instructions carefully.

In some countries, including the USA, you can buy melatonin without a prescription, as a dietary supplement. It is available on prescription only in other countries, including the UK.

Can you overdose on melatonin?

As long as you follow the recommendations from your doctor, as well as the instructions on the packet, you will avoid taking too much melatonin.

Difficulty sleeping can be really hard to cope with, though, so some people may take more melatonin than they should. It’s unknown whether you can overdose on melatonin.

However, if you’ve taken more melatonin than you should and you start to feel unwell, you should seek medical advice straight away. If you need to go to hospital, ask someone to go with you and don’t drive, as you might start to feel very sleepy.

While overdosing is unlikely, taking any amount of melatonin can cause side effects, including:

  • tiredness during the day
  • headache
  • tummy ache or feeling sick
  • dizziness
  • feeling irritable (easily annoyed) or restless
  • dry mouth
  • dry or itchy skin
  • pain in arms or legs
  • odd dreams or night sweats

If any of these side effects is bothering you or doesn't go away, speak to your doctor.

Who shouldn’t take melatonin?

Also bear in mind that certain groups of people shouldn’t take melatonin, as it might not be safe for them. You should discuss it with your doctor if you have:

  • had an allergic reaction to melatonin or any other medicines in the past
  • liver and kidney problems
  • epilepsy
  • rheumatoid arthritis, multiple sclerosis, lupus or another autoimmune condition

It is best to avoid taking melatonin if you’re pregnant or breastfeeding, too, as it’s not known if it’s safe for you and your baby.

When to see a doctor

There are some rare but serious side effects connected to melatonin. Speak to your doctor as soon as possible if you:

  • start to feel sad or low (this could be depression)
  • have blurry vision or get watery eyes
  • feel faint or pass out
  • feel dizzy or confused, or feel like things are spinning (vertigo)
  • have any bleeding that doesn’t stop, unexplained bruising, or blood in your pee
  • get red, flaky skin (psoriasis)

Very rarely, melatonin can cause a serious allergic reaction called anaphylaxis, or chest pain and suddenly noticeable heart beats (heart palpitations). In these cases, you should call for emergency medical help.

Key points

  • our body produces melatonin when it’s dark, to help us sleep
  • if you’re having sleeps problems, such as insomnia or jet lag, melatonin supplements may help
  • talk to your doctor about how much melatonin to take, and to check it’s suitable for you
  • taking melatonin can cause side effects, which can occasionally be serious
  • it’s unknown if you can overdose on melatonin – but it’s unlikely if you follow the advice
  • if you’ve taken too much melatonin and you feel unwell, seek medical advice immediately
Was this article helpful?

We include references at the end of every article, so you know where we get our facts. We only ever take evidence from medically-recognised sources, approved by the UK National Health Service's The Information Standard, or certified by Health On the Net (HON). When we talk about popular health trends or claims, we'll always tell you if there's very little or no evidence to back them up. Our medical team also checks our sources, making sure they're appropriate and that we've interpreted the science correctly.

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.