Jet lag

Medical information

Written and reviewed by a team of doctors. Dr Fox is regulated by the CQC & GPhC.

About jet lag and melatonin treatment

Melatonin 3mg tablets are licensed in the UK to treat and prevent jet lag. Melatonin is a natural hormone that helps regulate the body's day night rhythm - the body clock. In jet lag, the internal body clock is out of sync with the actual time zone, due to rapid travel between time zones.

How does melatonin work?

Taking extra melatonin at bedtime, can help the body clock to adjust more quickly. By replacing the usual surge of melatonin the body produces before sleep, so the symptoms of jet lag can be reduced. Melatonin should encourage sleep but it is not a sleeping tablet.

Who can benefit from jet lag treatment?

Melatonin 3mg is for use by adults only (over 18s). Travellers crossing five or more time zones, particularly on eastbound flights (for example, from the UK to Asia or Australia), where jet lag tends to be more noticeable.

It may be especially helpful if you:

• Have difficulty falling asleep at your destination.
• Need to be alert soon after arriving, such as for work or an event.
• Have experienced troublesome jet lag on previous trips.
• Are staying for several days or longer and want to adjust to the new time zone more quickly.

Dr Fox can only prescribe melatonin for jet lag not for other conditions such as chronic insomnia or shift work.

How to take melatonin for jet lag

Once arrived at your destination, take one or two 3mg tablets daily at bed-time. Go to bed at the same time in your new time zone as your usual bedtime.

Take two tablets if one does not work. Do not take before 8pm or after 4am. Best taken with liquid (not alcohol) preferably on an empty stomach (no food for 2 hours before and after). Forgotten tablets can be taken late, but not after 4am. Do not take double doses to make up for a missed dose.

A full course is 5 days, but you can stop early if symptoms have settled.

Taking more than the recommended dose (overdose) is likely to cause drowsiness, headache, dizziness, and nausea. Seek medical advice if you do not feel well.

A pack of 30 melatonin 3mg tablets is sufficient to treat between 3 and 6 episodes of jet lag, depending on whether one or two tablets are taken each day. The maximum number of treatments is 16 per 12 months (160 tablets).

Who should NOT take melatonin?

Some people with pre-existing medical conditions or taking certain medications should not take melatonin. This includes people with epilepsy, autoimmune disease, diabetes and kidney and liver impairment. A full list of interacting medicines can be found in the patient information leaflet supplied with the melatonin tablets. Checks for suitability are carried out in the online consultation which is part of the ordering process.

Possible side effects of melatonin and cautions

As with all medicines, some people experience side effects, although in most cases these are not serious.

Contact a doctor immediately if you develop any of these uncommon but serious side effects:

• Chest pain (uncommon affecting 1 in 100).
• Palpitations, fainting, disorientation, visual symptoms (1 in 1000).
• Allergic reactions including swelling of the tongue and mouth.

Rarely (1 in 1000) there can be effects on the blood leading to fewer white blood cells or platelets and this may cause bruising, bleeding or blood in the urine, or an increased infection risk. Contact a doctor if you develop any of these symptoms.

Up to 1 in 10 people may experience headache or daytime drowsiness. Sometimes women, and occasionally men, may experience milk leakage from the breasts. More information on side effects is found in the manufacturer's patient information leaflet.

Melatonin and pregnancy, or breastfeeding

The effects of melatonin on unborn babies and breast-fed infants is unknown and therefore melatonin should not be taken in pregnancy or when breastfeeding. Women who could become pregnant whilst taking melatonin must use effective contraception.

Other measures to help with jet lag

• Before you travel try going 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 of water 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 at destination times.
• Stay in a dark bedroom during the night, even if you are awake.
• 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 (Seasonal Affective Disorder) light at these times.

Dr Fox pharmacy supplies melatonin 3mg medication on prescription – you are required to answer a short medical questionnaire before your order can be completed.

Authored 14 February 2020 by Dr Tony Steele
MB ChB Sheffield University 1983. Former hospital doctor and GP. GMC no. 2825328

Reviewed by Dr J. Tweedie, Dr C. Pugh, Dr B. Babor
Last reviewed 17 July 2026
Last updated 21 September 2026
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