Melatonin

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.