What should you know about high altitude tiredness?

At altitude, the air contains less available oxygen with each breath. Your body may respond with faster breathing and a quicker heartbeat, leaving you unusually tired during walking or routine tasks. Travel, cold, poor appetite and unfamiliar sleep conditions can add to the strain.

Mild tiredness may improve after rest and time to acclimatise. Headache, nausea, dizziness or breathlessness at rest can signal altitude illness rather than ordinary exertion. Fatigue that continues after returning to lower ground may have another cause, such as [Dehydration](/conditions/dehydration/) or [Anaemia](/conditions/anaemia/).

Reduce exertion, rest, keep warm and drink regularly. Avoid alcohol while symptoms are present, and do not climb higher if you feel unwell. Allow gradual acclimatisation before strenuous activity; travelling down is the key response if symptoms are worsening.

Record when the tiredness began, your approximate altitude, recent activity, fluid intake and any accompanying symptoms. A clinician can also consider conditions such as [COVID-19](/conditions/covid-19/) or [Chronic Fatigue Syndrome](/conditions/chronic-fatigue-syndrome/) when fatigue does not fit the altitude pattern.

Seek urgent medical help for breathlessness at rest, confusion, difficulty walking, fainting, blue-tinged lips, severe headache, repeated vomiting or a cough producing frothy sputum. Move to a lower altitude with assistance if altitude illness is suspected, and do not wait for symptoms to become extreme.

Ask whether your symptoms fit acclimatisation, whether medicines or existing conditions affect altitude travel, and what warning signs should prompt descent. Mention sleep disruption, alcohol use, snoring, recent illness and symptoms that remain at sea level.