A mother comforting her sad daughter

Your guide to medication Melatonin

Melatonin is a hormone that can be taken as a medication to help treat insomnia and sleep problems.

Medication name: Melatonin ("MEL-a-TOE-nin")
Brand names: Circadin¼ ("SER-ka-din"), Slenyto (“SLEN–e-toe”)
Medication type: Hormone

Ways to take melatonin
Tablets*: 1mg, 2mg, 3mg and 5mg strengths
Liquid**: 1mg in 1ml

*Some melatonin tablets are modified-release, meaning the medicine gets into your body more slowly over a few hours.

**It is also available as a sugar-free liquid.

There are other strengths and preparations available, including capsules, but they need to be ordered specially by the pharmacist.

What can it be used for?
Melatonin is licensed to treat sleep problems in adults over 55 years of age. It can also be prescribed in adults of all ages for treatment of jet-lag.

Children with certain medical conditions may be prescribed melatonin as a licensed product but much prescribing in children and young people will be ‘off-label’ if your doctor believes the potential benefits outweigh any risks.

Your doctor should discuss the reasons why they believe this is the right medication for you before you start taking it.

Read our guide to sleep problems

About melatonin

How melatonin works

Melatonin is a hormone that occurs naturally in the body. It helps regulate your body clock so you can sleep better.

Melatonin will usually be given to you by a specialist at a hospital at first.

Melatonin should be used alongside good “sleep hygiene” techniques. These include: 

  • making sure that your room is dark and the right temperature
  • avoiding looking at backlit screens around bedtime
  • doing exercise during the day (but not the last couple of hours before bed)
  • avoiding taking naps during the day

The aim of using melatonin is to establish a good sleeping pattern with the lowest effective dose.

Read our guide to sleep problems

Melatonin and everyday life

Frequently asked questions

Melatonin starts to work about an hour after you take the dose. However, it can take a few days of taking melatonin for its full effect to develop.

Melatonin will start helping your body to re-establish a normal sleep pattern after you have taken it for a week or so.

The effects of a dose of melatonin can last for around four to eight hours after taking it.

A side effect of melatonin can be weight gain.

It is classed as ‘uncommon’, which means it effects less than one in 100 people who take it.

Talk to your doctor about this if it worries you.

You may want to let your family and friends know you are taking melatonin so they can support you and help you look out for side effects.

For guidance on this, check out our page on getting support with your medication.

Most people get helpful effects from melatonin for their sleep.

In some people, there can be side effects that make their sleep worse, such as strange dreams/nightmares, and waking up early.

If melatonin is making your sleep worse, go back to your doctor to discuss trying something else.

Alcohol

If you drink alcohol while taking melatonin, the alcohol will stop the melatonin from working as well.

Alcohol reduces the quality of your sleep and may make you feel drowsy the next day.

This is very important if you need to drive, ride a bike, or operate machines.

Smoking

You may need to change your dose of melatonin if you stop or start smoking.

Chemicals in the smoke make your liver break down the melatonin more quickly.

If you smoke, you will probably need a higher dose of melatonin than someone who does not smoke.

Tell your doctor if you smoke before you start taking melatonin to make sure you get the right dose for you.

Go to your doctor for advice if you stop or start smoking.

There is no effect from 'stop-smoking products' or e-cigarettes (vapes) on melatonin.

Melatonin can interact with some other medicines and drugs.

Tell your doctor or pharmacist if you take any other medicines including those you buy over the counter for common illnesses or apply to the skin.

Avoid drinking too many caffeine drinks (coffee, cola or energy drinks) while you are taking melatonin - especially at bedtime.

Caffeine is a stimulant and therefore has the opposite effect of melatonin in your body, reducing its impact.

Caffeine can cause anxiety and sleep loss; stopping these drinks might help to improve your symptoms.

Let your pharmacist know if you have any food allergies or intolerances, and always check with them if you’re concerned about any of the ingredients in your medication.

Do not drive a car or ride a bike just after you start taking melatonin.

Taking melatonin may affect your eyesight and make you feel tired or dizzy when you start taking it.

This could affect you if you drive a car, ride a bike, or do anything else that needs a lot of focus. It might be best to stop doing these things for the first few days, until you know how it affects you.

Don't worry – most people do these things as normal while taking melatonin.

Pregnancy and post-natal

There is very little information available about the effect of melatonin on a developing or newborn baby.

If you are trying for a baby or become pregnant while taking melatonin please talk to your doctor.

Breastfeeding

Natural melatonin is passed to the baby in breastmilk. Some of the extra prescribed melatonin will pass to your baby but is not thought to be harmful.

If your baby was born early, then breastfeeding with extra melatonin on board is not recommended as your baby may not be able to safely get rid of the extra melatonin.

Stop breastfeeding and quickly seek medical advice if your baby becomes restless, very sleepy, or develops feeding problems.

For more guidance, talk to your doctor or midwife about your feeding options.

Sex

Melatonin can have side effects that may affect your sex life. These might include:

  • low mood, which makes you feel less like having sex
  • hot flushes and excessive sweating in women
  • increased libido (sex drive)

The good effects of melatonin may have a positive impact on your sex life as your sleep improves, and you can concentrate on your relationships.

Some of these effects may pass after the first couple of weeks. If they do not, and this is a problem for you, go back to the doctor and see what else you could try.

Fertility

There is no information available about whether melatonin can affect your ability to get pregnant, but it is unlikely as it is a natural hormone.

Melatonin is not a banned substance in sport.

You might find that melatonin makes you feel sleepier, so if you are doing sports where you must concentrate with intensity (like driving, gymnastics, shooting etc.) You might want to stop playing these sports until you know how melatonin affects you.

Don't worry – most people play sports as normal while taking melatonin.

Try not to take melatonin for the first time just before your exams.

Melatonin can cause tiredness, eyesight problems and headaches in some people.

You should talk to your doctor about any future exams if you are starting melatonin. You might decide together to delay starting it until you have done them. If they are more than a week away, however, you might find that it is better to start melatonin to improve your sleep and your ability to study.

Don't worry – most people take exams as normal while taking melatonin.

Your doctor should know

  • You need to talk to your doctor or pharmacist before starting treatment with melatonin if any of the following apply to you:

    • you have an autoimmune disease like juvenile arthritis, multiple sclerosis, lupus or type 1 diabetes
    • you have liver or kidney disease
    • you have allergies to melatonin or lactose

Uses, warnings, safety and side effects

Taking melatonin

How long will I need to take melatonin for?

You and your doctor should talk about how long you need to take melatonin before you begin treatment.

Some people taking melatonin to help with sleep may take it for up to 13 weeks (three months) to make sure a normal sleep pattern is established.

Some people may need to take melatonin for longer (on the advice of their doctor).

People with attention deficit hyperactivity disorder (ADHD) usually only need to take melatonin for three to four weeks to get a normal sleep pattern again.

To get the best effect from melatonin, it is best not to miss any doses.

Keep taking the melatonin until you and your doctor agree that it is no longer needed.

You should only take melatonin as agreed with your doctor

Make sure that you know your dose. If it is not written on the label, check with your pharmacist or doctor.

Take your melatonin one to two hours before you go to bed, and after some food. This can be a small snack before bedtime, like a biscuit or two, if you have your evening meal more than two hours before you go to bed.

Do not break or chew the modified-release tablets. This is because they have a special system in them to deliver the medicine into your body slowly, over a few hours. Swallow the tablet whole with at least half a glass of water while sitting or standing.

You should make sure that you do not watch TV or use a computer or mobile phone at least an hour before going to bed, as light from these can stop your body from making its own melatonin.

What if I miss a dose?

If you remember later during the evening, before you go to bed, take it as soon as possible.

If you forget to take it by bedtime, just start again the next evening.

Do not take a double dose.

What will happen if I forget to take my melatonin?

If you forget to take your tablets for a few days, you may get your old symptoms back. This means that you should talk to your doctor about it.

You do not get discontinuation or withdrawal symptoms if you forget to take melatonin.

Stopping the use of melatonin

You should not get any harmful discontinuation or withdrawal effects if you stop taking melatonin.

However, you may get your old symptoms back.

If you are on a high dose, then the doctor may wish to reduce the dose slowly before stopping it completely.

Warnings and safety

Safety headlines

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.

When to see your doctor

There have been no cases of harm in overdose with melatonin. If you have taken more melatonin than it said on the label, you might become very sleepy. Stay somewhere safe, with a friend or family member to watch you while you sleep off the effects. Tell your doctor or pharmacist as well. It should take about 12 hours for your body to deal with the extra doses. Do not try to drive or do anything that could be dangerous to yourself or others.

Stop taking melatonin and go to a doctor straight away if you get any of the following symptoms:

  • fainting or losing consciousness
  • dizziness or vertigo (which may feel like ‘spinning’)
  • feeling mixed up and confused (disorientated)
  • severe chest pain, or changes in heartbeat
  • depression (feeling low)
  • problems with your eyesight
  • blood in your wee
  • unusual bleeding or bruising
  • a flaky pink/red rash on your skin, particularly on your elbows and knees, called psoriasis

Side effects

Side effects

Please do not be worried by the side effects listed on this page. Many people take melatonin without any side effects or with only a few mild side effects. If you think you might be getting a side effect from melatonin, then you should discuss this with your doctor, nurse, or pharmacist.

Common side effects (affecting up to one in 10) people include:

  • headaches – speak to your pharmacist about pain relief (like paracetamol) if you experience this side effect
  • occasional muscle pain
  • changes in mood, feeling strange

Please look at the leaflet inside your medicine box, or ask a doctor or pharmacist, if you want to know whether you are getting a side effect from your medicine.

If you do get a side effect, please think about reporting it via the Yellow Card Scheme.

If you want to stop taking melatonin, speak to your doctor to discuss the options available to you.

Taking melatonin

How long will I need to take melatonin for?

You and your doctor should talk about how long you need to take melatonin before you begin treatment.

Some people taking melatonin to help with sleep may take it for up to 13 weeks (three months) to make sure a normal sleep pattern is established.

Some people may need to take melatonin for longer (on the advice of their doctor).

People with attention deficit hyperactivity disorder (ADHD) usually only need to take melatonin for three to four weeks to get a normal sleep pattern again.

To get the best effect from melatonin, it is best not to miss any doses.

Keep taking the melatonin until you and your doctor agree that it is no longer needed.

You should only take melatonin as agreed with your doctor

Make sure that you know your dose. If it is not written on the label, check with your pharmacist or doctor.

Take your melatonin one to two hours before you go to bed, and after some food. This can be a small snack before bedtime, like a biscuit or two, if you have your evening meal more than two hours before you go to bed.

Do not break or chew the modified-release tablets. This is because they have a special system in them to deliver the medicine into your body slowly, over a few hours. Swallow the tablet whole with at least half a glass of water while sitting or standing.

You should make sure that you do not watch TV or use a computer or mobile phone at least an hour before going to bed, as light from these can stop your body from making its own melatonin.

What if I miss a dose?

If you remember later during the evening, before you go to bed, take it as soon as possible.

If you forget to take it by bedtime, just start again the next evening.

Do not take a double dose.

What will happen if I forget to take my melatonin?

If you forget to take your tablets for a few days, you may get your old symptoms back. This means that you should talk to your doctor about it.

You do not get discontinuation or withdrawal symptoms if you forget to take melatonin.

Stopping the use of melatonin

You should not get any harmful discontinuation or withdrawal effects if you stop taking melatonin.

However, you may get your old symptoms back.

If you are on a high dose, then the doctor may wish to reduce the dose slowly before stopping it completely.

Warnings and safety

Safety headlines

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.

When to see your doctor

There have been no cases of harm in overdose with melatonin. If you have taken more melatonin than it said on the label, you might become very sleepy. Stay somewhere safe, with a friend or family member to watch you while you sleep off the effects. Tell your doctor or pharmacist as well. It should take about 12 hours for your body to deal with the extra doses. Do not try to drive or do anything that could be dangerous to yourself or others.

Stop taking melatonin and go to a doctor straight away if you get any of the following symptoms:

  • fainting or losing consciousness
  • dizziness or vertigo (which may feel like ‘spinning’)
  • feeling mixed up and confused (disorientated)
  • severe chest pain, or changes in heartbeat
  • depression (feeling low)
  • problems with your eyesight
  • blood in your wee
  • unusual bleeding or bruising
  • a flaky pink/red rash on your skin, particularly on your elbows and knees, called psoriasis

Side effects

Side effects

Please do not be worried by the side effects listed on this page. Many people take melatonin without any side effects or with only a few mild side effects. If you think you might be getting a side effect from melatonin, then you should discuss this with your doctor, nurse, or pharmacist.

Common side effects (affecting up to one in 10) people include:

  • headaches – speak to your pharmacist about pain relief (like paracetamol) if you experience this side effect
  • occasional muscle pain
  • changes in mood, feeling strange

Please look at the leaflet inside your medicine box, or ask a doctor or pharmacist, if you want to know whether you are getting a side effect from your medicine.

If you do get a side effect, please think about reporting it via the Yellow Card Scheme.

If you want to stop taking melatonin, speak to your doctor to discuss the options available to you.

About this information

The information on this page was reviewed by the College of Mental Health Pharmacy in March 2020.

Visit the CMHP website
college of mental health pharmacy logo

CMHP. College of Mental Health Pharmacy

Find out more about mental health medication

Taking medication for your mental health can feel daunting, but we have lots of information and advice that can really help.