Melatonin

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

• Cigarette smoke affects the amount of melatonin in your body.
• Chemicals in the smoke make your liver break down the melatonin more quickly in your liver.
• If you smoke, you will probably need a higher dose of melatonin than someone who does not smoke.
• Tell your doctor if you smoke, so that you get the right dose for you.
• If you stop smoking while taking melatonin, the level of melatonin rises and you might need to reduce your dose.
• If you (re)start smoking, you will probably need to increase it again
• Go to your doctor for advice if you stop or start smoking.
• There is no effect from stop smoking products or e-cigarettes on melatonin.

Melatonin does not mix well with street drugs or legal highs

• Melatonin may not mix well with street drugs or legal highs. There are no reports of extra problems with melatonin and street drugs but that doesn't mena they're safe. 
• The combined effects of melatonin and opiate street drugs like heroin and methadone are likely to make you very sleepy.

Stopping this medicine quickly, or reducing the dose too much at once, does not have any harmful effects, but your sleep problems may return

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

Melatonin is not addictive and you cannot become tolerant to its effects

• Melatonin is not addictive and you cannot become tolerant to its effects regardless of how long you take it for.

Do not drink alcohol while you are taking melatonin as it will stop it from working properly.

• 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.

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

• Taking melatonin may make you feel tired or dizzy, and may affect your eyesight, 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.

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 do exams as normal while taking melatonin.

Melatonin is not a banned substance in sport

• You might find that melatonin makes you feel more sleepy, so if you are doing sports where you have to focus, like driving, gymnastics, shooting etc, you might want to stop until you know how melatonin affects you
• Don't worry –most people do sports as normal while taking melatonin.

Your weight can be affected by melatonin

• A side-effect of melatonin can be weight gain
• It is classed as ‘uncommon’, which means it can affect up to 1 in 100 people who take it
• Talk to your doctor about this if it worries you

Melatonin may make you feel sleepy, but rarely may also make it hard to get to sleep

• 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 try something else

Let your family and friends know you are taking melatonin so they can support you and help you look out for side effects

• It might actually be a great idea to choose a good friend to tell about your medicine when you start taking it. (Or – even better – to take one with you to the doctor before you start taking it!)
• They could look at the medicine leaflet, or at this website.
• They could help you to understand whether the medicine changes your behaviour, or gives you side-effects (sometimes it’s hard for us to see it ourselves).
• Melatonin does not often cause side effects. However, some side effects could put a strain on your friendships and relationships.
• These side effects include headaches, dizziness, and feeling irritable, nervous, or low in mood.
• These side effects often get better after a few days, and you will start getting the good effects of melatonin. This should help improve your relationships.
• If the side effects don’t get better, or if you are worried about them, then you should discuss them with your doctor.

Melatonin can have side-effects that might affect your sex life

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

There are some side-effects that include:

• You might feel more like you want to have sex
• You may get a low mood and feel less like having sex
• Women might find they are getting hot flushes or sweats like going into the menopause
• You may not feel as sexy if you put on any weight, or if you get rashes on your skin from the medicine.

These effects should 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.

We do not know if melatonin can affect your ability to get pregnant (fertility)

• There is no information available about whether melatonin can affect your ability to get pregnant (fertility).

We do not know much about the effects of melatonin in pregnancy

If you take melatonin and you are thinking of becoming pregnant, or if you discover that you are pregnant, then you should speak to your doctor.

• There is only a little information available about the effect of melatonin on a developing or newborn baby.
• Animal studies did not show effects on the developing baby
• Animal studies showed a slight effect on the growth of a newborn baby, but only when extremely high doses (2000mg/day!) of melatonin were used.
• It is probably best not to use melatonin if you are pregnant, or trying to get pregnant.
• Melatonin is passed to the baby in breastmilk whether you take extra melatonin in tablet form or not. It is likely that melatonin from tablets is also passed on to the baby and so it is not recommended to breastfeed while taking medication.
• Talk to your doctor or midwife about your feeding options.

Avoid drinking too many caffeine drinks especially at bedtime while you are taking melatonin

• Caffeine is a stimulant and therefore has the opposite effect of melatonin in your body, and reduces the effect of the melatonin.
• Try to avoid drinking too many drinks with caffeine in (like coffee, cola or energy drinks) while you are taking melatonin especially at bedtime.
• Caffeine can cause anxiety and sleep loss – stopping these drinks might help to improve your symptoms.

Reference sources

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