What should you know about really bad jet lag?

Your internal clock may still signal sleep or wakefulness according to your departure time. This mismatch can cause difficulty sleeping at the local bedtime, early waking, daytime sleepiness, poor concentration, headache, appetite changes and low mood. Symptoms can feel stronger after a long journey, several time-zone changes, dehydration, illness or sleep loss. Jet lag is different from an infection, although travel can happen alongside one.

Persistent symptoms may need assessment for insomnia, medication effects or another health problem rather than being attributed to travel alone.

Follow local time for meals, light exposure and sleep as soon as practical. Seek outdoor daylight at a useful local time, keep naps short or skip them if they prevent night sleep, drink water, eat lightly if your stomach is unsettled, and use gentle movement. Keep the bedroom dark and quiet. Avoid alcohol and do not drive, swim alone or operate machinery while very sleepy. A travel-health clinician can advise about timing strategies and medicines for your itinerary.

Seek medical advice if symptoms are severe, continue after your body clock should have adjusted, or stop you functioning safely. Get urgent help for chest pain, fainting, severe breathlessness, new confusion, weakness on one side, a sudden severe headache, or thoughts of self-harm. Fever, persistent vomiting or signs of dehydration also deserve prompt assessment.

Ask how to time light, sleep and any recommended treatment for your travel direction and schedule. Tell the clinician about pregnancy, chronic conditions, prescribed medicines, supplements, alcohol use and whether you must drive or work immediately after arrival.