What should you know about sudden extreme fatigue?

The word extreme describes how strongly fatigue affects you, not a diagnosis. A sudden crash may accompany a viral infection, COVID-19, poor sleep, heat exposure, dehydration or a missed meal. Longer-lasting tiredness can occur with anaemia, coeliac disease, chronic kidney disease, burnout, chronic fatigue syndrome or alcohol use disorder. A condition can present with fatigue, but fatigue by itself does not establish which condition is present.

Record the change from your usual energy. Note sleep quality, recent stress, new medicines, alcohol, appetite, fluid intake, pain, fever, cough, bowel changes and breathlessness. This information helps separate a short-lived trigger from a problem requiring tests.

Sit or lie down if standing feels difficult. Sip fluids, rest in a cool and quiet place, and have food if you have not eaten and can swallow safely. Do not use extra caffeine or someone else’s medicine to push through the episode. Avoid driving, swimming alone or operating equipment until your alertness returns. Contact a clinician if the fatigue remains intense, returns repeatedly or stops you managing basic activities.

Call emergency services for extreme fatigue with trouble breathing, chest pressure, fainting, new confusion, difficulty speaking, sudden weakness, a severe allergic reaction or blue lips. Seek same-day advice if you cannot keep fluids down, are passing very little urine, have a severe infection-like illness or are rapidly deteriorating. A person who is difficult to wake needs emergency help.

Ask whether your symptoms suggest an infection, anaemia, a metabolic problem, sleep disruption or another cause; whether testing is appropriate; and how to manage activity while recovering. Tell the clinician exactly what you were doing when the fatigue began.