What is the circadian rhythm?

This is the technical term for the body's internal 'body clock', which regulates a lot of body functions, including hormone production especially melatonin and cortisol, kidney function, and the sleep/wake cycle. The clock is kept to time by the pineal gland in the brain which responds to the hours of daylight and darkness. It is the mismatch between the circadian rhythm and daylight/night in a new time zone which leads to symptoms of jet lag.

What is the role of cortisol in jet lag?

Cortisol is a hormone which is produced in the last few hours of our sleep, to wake us up for the day ahead. Lack of appropriately timed cortisol production plays a part in the symptoms of wakefulness during the night and lack of concentration, motivation and daytime drowsiness of jet lag. It takes a day per hour of time change for cortisol production to adjust to a new time zone.

What is the role of melatonin in jet lag?

Melatonin is a natural hormone made in the pineal gland in the brain. It is produced by the body to prepare the body for sleep. Melatonin helps to regulate the body clock and natural production is triggered by darkness. When travelling across time zones the body takes time to adjust melatonin production to the new light/dark cycle and this contributes to symptoms of jet lag. By taking extra synthetic melatonin as tablets at bedtime, the body is encouraged to sleep at appropriate times and this can help with body clock adjustment.

What are the symptoms of jet lag?

Jet lag is caused by the mismatch of the body clock with the local time zone. Symptoms can include difficulty dropping off or staying asleep, daytime sleepiness, loss of concentration and motivation, headaches, irritability, reduced appetite, and bloating. Symptoms tend to be worse after travelling across more time zones, especially if there is more than 5 hours difference. Symptoms are worse travelling East as the body struggles more to adapt to going ahead in time than backwards.

Why is jet lag worse when travelling to the East?

To adjust to new time zones the brain needs to adjust production of the hormones melatonin and cortisol to the new time zone. If heading West this means delaying production which is easier to do, than the speeding up of production needed when heading East. Without the sleep-inducing melatonin it is more difficult to sleep when not feeling tired if travelling to the East.

How should I take melatonin 3mg tablets to help with jet lag?

Melatonin 3mg tablets are licensed in the UK for jet lag. The dose is 1 or 2 tablets taken at bedtime on arrival at your destination for a maximum of 5 days. Start with 1 tablet and increase to 2 if it is not fully effective. The tablets should help you to sleep within a couple of hours of taking. Do not take melatonin before 8pm or after 4am. A missed dose can be taken during the night but not after 4am. Do not take 2 doses together. Do not have food within 2 hours of the dose (before or after the tablets).

Do I start to take melatonin before I leave home?

No. Melatonin should be started at bedtime on your first night in the new time zone.

What else can I do to help with jet lag?

  • Before you travel go to bed at a time closer to the destination bedtime. Make sure you have enough sleep in the days before you travel.
  • Keep as calm and relaxed as possible during travel.
  • Drink plenty to keep hydrated, especially during the flight.
  • Avoid alcohol.
  • Move around during the flight when you can.
  • Adjust the time on your watch to the destination time at the start of the flight.
  • Sleep during the journey only during 'night time hours' on destination time.
  • On arrival try to sleep and eat according to destination times.
  • Stay in a dark bedroom, even if you are awake, during the night.
  • Try to avoid naps during the day.
  • Spend time out of doors, especially in the afternoons if travelling west, and in the mornings if travelling east, as bright natural light helps with adjustment. Alternatively use a SAD light at these times.

How often can I take melatonin 3mg for jet lag?

A course of melatonin 3mg lasts 5 days, whether taking 1 or 2 tablets each night. The manufacturer recommends taking no more than 16 courses per year. At least 3 weeks should usually be left between courses of melatonin for jet lag. The body needs time to adjust its own production of melatonin to a new time zone, and repeated time zone changes using synthetic melatonin is very disruptive.

Is melatonin available on the NHS?

Melatonin 3mg tablets are only licensed for treating and preventing jet lag in the UK and as they are travel medicines, they are not available on the NHS. Melatonin 2mg slow release capsules (Circadin) are available in certain cases on the NHS for treating insomnia.

Why can't I buy melatonin supplements in health food shops in the UK?

Melatonin is a prescription-only drug in the UK, not a health supplement. In many other countries it is classed as a health supplement and is available to buy in health food shops.

Can I buy melatonin from abroad and get them delivered to me in the UK?

Melatonin sold as health supplements is less well regulated than prescription medicine. If buying from abroad, the melatonin supplements may contain varying amounts of active melatonin, no melatonin at all, or even potentially hazardous ingredients not listed on the label according to a 2017 study. As melatonin is a prescription-only medicine in the UK, it is illegal to sell or redistribute imported melatonin.

Can I drink alcohol while taking melatonin?

No. It is not recommended to drink alcohol when taking melatonin as alcohol can disturb sleep. It also worsens symptoms of jet lag.

What about food and drink with melatonin?

Melatonin tablets should not be taken within 2 hours of food, so eat your evening meal well before going to bed and don't get up and snack in the night. Caffeine in drinks is a stimulant and will work against melatonin at night, but can be taken in the mornings.

Do melatonin 3mg tablets contain lactose?


Is melatonin safe to use?

There have been many studies about short-term use of prescription melatonin for jet lag and it appears to be safe. There are a few people who cannot take melatonin because of health issues or other medications. At present there is no safety data if melatonin is taken for prolonged periods.

Can I take melatonin when pregnant or breastfeeding?

Melatonin is found in breast milk and also reaches an unborn child through the placenta. The effect of this is not known and so melatonin should not be used if pregnant, trying to get pregnant, or if breastfeeding.

Does melatonin cause sleepwalking?

No. But if you are known to sleepwalk you may be more at risk from sleepwalking in a strange environment after travelling.

Is melatonin addictive?

Melatonin is not a sleeping tablet (hypnotic) so there is no addiction risk.

Is it safe to drive, ride a bicycle, or operate machinery after taking melatonin?

Melatonin will make you drowsy in the hours after taking it and you should not drive, ride a bicycle, or operate machinery. Jet lag may also make it unsafe if you are troubled by daytime drowsiness. Think twice about driving immediately after arriving in any new time zone.

What medication affects melatonin?

The effect of melatonin is increased and these medications should not be taken at the same time as melatonin:

  • Fluvoxamine for depression, OCD (obsessive compulsive disorder).
  • Psoralen as part of PUVA light treatment for skin conditions like psoriasis.
  • Cimetidine rarely used for stomach acid.
  • Oestrogen in combined contraceptives or HRT (hormone replacement).
  • Quinolone antibiotics rarely used, e.g. ciprofloxacin, moxifloxacin.
  • Other sleeping tablets or remedies.

The following medications decrease the effect of melatonin and should not be taken at the same time:

  • Rifampicin antibiotic for tuberculosis.
  • Carbamazepine for epilepsy, bipolar disorder, and trigeminal neuralgia.

Warfarin may be affected by melatonin, but newer NOAC anticoagulants like dabigatran and apixaban are not affected. Discuss with your GP.

Do recreational drugs affect melatonin?

Stimulant drugs will prevent melatonin from working and others may cause problems by adding to drowsiness. They should not be used at the same time as taking melatonin.

Will melatonin affect my contraception?

Contraceptives will still work, but melatonin levels are increased by oestrogen in combined hormonal contraceptives, and in HRT. Progesterone only methods of contraception and barrier methods are not affected. If planning to take melatonin, discuss with your GP or contraceptive provider in plenty of time before travel.

Does melatonin prevent or treat COVID-19?

No. There is no evidence that melatonin helps in any way with COVID-19.

Can melatonin be used to treat other conditions?

Melatonin has been studied as a treatment for a variety of other conditions. These include Gastroesophageal reflux disease (GERD), as a support to cancer treatments (e.g. radiotherapy, chemotherapy), endometriosis, high blood pressure, menstrual pain, general insomnia, shift work related insomnia, frequent urination at night (nocturia), migraine prevention, anxiety before surgery, sunburn prevention, jaw pain from temporomandibular joint problems, age related macular degeneration in the eyes, winter depression (SAD), Alzheimer's disease, tinnitus, and COVID-19.

Unfortunately, many of the studies have been in very small numbers of patients and have been unreliable. At present there is no UK licence for melatonin to be used to treat anything except jet lag and short term insomnia.

Do coloured glasses help with jet lag?

Melatonin production is affected by light and dark, and is especially reduced by blue light. By wearing glasses that block blue light it may help to increase natural melatonin production. They should be worn for a couple of hours before bedtime, once at your destination.

What should I do about jet lag if only travelling to a new time zone for 2 or 3 days then returning?

If you will only be in a different time zone for a very short time, then it is recommended to maintain the sleep/eat times of your normal time zone, rather than encouraging your body to adjust to the new zone.

Do exercise and outdoor light help with jet lag?

Exercise can stimulate cortisol production and bright light reduces melatonin production, so this can be used to good effect to help with symptoms of jet lag.

If travelling East, exercising in the mornings especially outdoors may help. Bright natural light in the afternoons if travelling West, or mornings if travelling East, is also helpful. Some people find that using a SAD light to simulate bright outdoor light at these times will also help.

What is a SAD light?

SAD lights were originally developed to help people who suffer from Seasonal Affective Disorder (SAD). Depression develops during the dark winter months of lower light levels. The SAD light is a bright light box which is used for several hours a day to boost the body's light exposure and so helps lift the depression. As jet lag is also related to changes in light exposure, a SAD light can be used to encourage the body to adjust. Sitting in front of the light during the new mornings after travelling East and the new afternoons when travelling West, encourages the reprogramming of the body's internal clock to the new time zone. The light is absorbed through the eyes so despite its brightness, sunglasses or eye masks should not be worn.

Dr Amanda Wood

Authored 12 January 2022 by Dr A. Wood
MB ChB Manchester University 1984. Former NHS GP in Bristol. GMC no. 2855422

Reviewed by Dr C. Pugh, Dr B. Babor
Last reviewed 12 January 2022
Last updated 19 July 2024