Tiredness at altitude: causes and warning signs

At higher elevations, each breath delivers less oxygen to the body. Faster breathing, a higher workload during activity, disrupted sleep and the effort of travel can all reduce energy while acclimatisation develops.

Expected exertional fatigue usually eases with rest and does not steadily worsen. Fatigue that begins after ascent and comes with headache, poor appetite, nausea, dizziness or restless sleep can occur with acute mountain sickness.

Dehydration can also present with tiredness, thirst, dry mouth and darker urine. Anaemia and other health problems may become more noticeable during exertion at altitude, so persistent symptoms after returning lower deserve assessment.

Reduce exertion, eat regular meals, drink according to thirst and avoid alcohol or sedating medicines unless prescribed. Keep warm and allow time for sleep, but do not use sleep as a reason to ignore worsening symptoms.

Pause further ascent when unexplained fatigue appears. If it accompanies other altitude-sickness symptoms, remain at the same elevation until fully improved; descend if the symptoms become worse or fail to settle.

Seek urgent help and descend with assistance for confusion, fainting, inability to walk steadily, breathlessness at rest, blue or grey lips, chest pain, a wet cough or unusual difficulty staying awake. These are not features to manage by simply sleeping longer.

Medical review is also appropriate when fatigue continues at low elevation, repeatedly limits ordinary activity, or comes with bleeding, fever, unexplained weight change or persistent breathlessness.

Describe the highest sleeping elevation, ascent speed, symptom timing, medicines, fluid intake and whether rest or descent helped. Ask whether a blood count, oxygen assessment or review of heart and lung health is appropriate before another trip.