Frequently asked questions
What causes jet lag?
Jet lag happens when your body's internal clock, or circadian rhythm, falls out of sync with the time zone you have travelled to. This clock is normally set by light and darkness, and controls when you feel sleepy or alert, hungry or full. Crossing several time zones quickly, particularly by air, means your body has not had time to adjust, so it is still working to your old schedule while the world around you has moved on. The greater the number of time zones crossed, the longer it typically takes for your body clock to catch up.
Can jet lag be dangerous, or is it just unpleasant?
No, jet lag is not dangerous and does not pose a serious risk to health. It is a temporary disruption to your sleep-wake cycle rather than an illness, and for most people the main issues are tiredness, poor concentration and feeling generally out of sorts. Jet lag can make it harder to enjoy the first few days of a trip or perform well at work, but symptoms resolve on their own as your body clock adjusts. If you have an underlying health condition that jet lag is making harder to manage, or you are concerned, speak to a pharmacist or GP for advice.
What are the symptoms of jet lag?
The most common symptoms are fatigue, difficulty falling or staying asleep, and daytime sleepiness at your destination. Many people also notice poor concentration, irritability, mild headaches and a general feeling of being disorientated or "foggy". Digestive changes, such as constipation or an upset stomach, are also common, as your gut has its own internal clock that is disrupted alongside your sleep-wake cycle. Symptoms are usually most noticeable in the first two or three days after arrival and gradually ease as your body adjusts to the new time zone.
Will jet lag go away on its own without treatment?
Yes, jet lag will usually resolve without treatment as your circadian rhythm gradually re-syncs with the new time zone, though this can take several days. As a rough guide, your body clock adjusts by around one day for every time zone crossed, so a long-haul flight across eight or nine time zones could mean over a week of disrupted sleep. Melatonin can help speed this process up by signalling to your body that it is time to sleep at your new bedtime, which is why it is often used to shorten the duration and severity of jet lag on shorter trips.
Does everyone get jet lag, or are some people more affected than others?
Most people experience some degree of jet lag after crossing three or more time zones, but how badly you are affected varies from person to person. Age can play a role, as older adults sometimes take longer to adjust than younger travellers. The number of time zones crossed, the direction of travel and your sleep habits before flying all make a difference too. People who are already sleep-deprived before their flight, or who have a naturally rigid sleep schedule, often notice symptoms more than those who adapt their routine easily.
Does the direction you fly affect how bad your jet lag is?
Yes, most people find jet lag worse when travelling east than when travelling west. This is because eastward travel shortens your day, requiring you to fall asleep earlier than your body is used to, which is generally harder for the body clock to adjust to than staying awake later. Westward travel lengthens your day instead, and most people find it easier to delay their bedtime than to bring it forward. This is why the same length of flight can feel very different depending on whether you are flying towards or away from home.
How many days can you take melatonin for jet lag?
Melatonin for jet lag is usually taken as a 3mg tablet once a day, for up to five days, starting with your first dose at your normal bedtime on arrival at your destination. If needed, this can be increased to two tablets, but you should not use more than sixteen treatment courses of melatonin in a year. Melatonin is a prescription-only medicine in the UK for jet lag, so it needs to be prescribed following an online consultation or by your GP, who can confirm the correct dose and duration for you.
Can jet lag cause symptoms besides tiredness, such as digestive problems or mood changes?
Yes, while fatigue and disrupted sleep are the most recognised symptoms, jet lag can also affect your digestion, mood and concentration. Constipation, diarrhoea and general stomach discomfort are common, as your digestive system follows its own circadian rhythm that is thrown off alongside your sleep pattern. Irritability, low mood and difficulty focusing are also frequently reported, particularly in the first few days after a long-haul flight. These symptoms usually improve together with your sleep as your body clock adjusts to the new time zone.