What should you know about viruses that cause extreme fatigue?

During an infection, inflammation, disrupted sleep, reduced appetite and dehydration can all lower energy. COVID-19 may include fatigue alongside fever, cough, sore throat or changes in smell and taste, but symptoms vary. Extreme tiredness can also occur with [Anaemia](/conditions/anaemia/), [Coeliac Disease](/conditions/coeliac-disease/) or [Dehydration](/conditions/dehydration/), so fatigue alone cannot identify its cause. A clinician may ask about sleep, mood, medicines, diet, bleeding and recent illness.

Rest between essential activities, drink regularly, eat simple nourishing meals if able, and return to activity gradually as energy improves. Avoid driving or hazardous work when drowsiness affects concentration. Keep a brief record of when fatigue began, associated symptoms and how activity changes it. Do not use stimulants to push through marked exhaustion without advice. If fatigue continues, a clinician can consider causes such as [Chronic Fatigue Syndrome](/conditions/chronic-fatigue-syndrome/) or [Chronic Kidney Disease](/conditions/chronic-kidney-disease/) alongside infection.

Seek urgent help for severe breathing difficulty, chest pain, fainting, new confusion, inability to stay awake, or inability to keep fluids down. Arrange a medical review when fatigue is worsening, interferes with basic tasks, follows unexplained weight change, or persists after other symptoms settle. Ask for support promptly if low energy is accompanied by hopelessness or thoughts of self-harm.

Ask which symptoms point toward infection, whether blood tests or other checks are appropriate, and how to pace activity safely. Mention alcohol intake, sleep quality, stress and any recent medication changes; [Burnout](/conditions/burnout/) and [Alcohol Use Disorder](/conditions/alcohol-use-disorder/) can also affect energy.