What should you know about sudden tiredness during the day?

A poor night, disrupted sleep schedule, emotional strain or Burnout can reduce alertness. Dehydration may cause thirst, headache and low energy, while COVID-19 can cause tiredness with fever, cough or aches. Anaemia may bring fatigue, breathlessness or paleness; Coeliac Disease can cause digestive symptoms alongside low energy. Chronic Kidney Disease may be associated with tiredness and changes in urination. Alcohol Use Disorder can disrupt sleep and affect energy between periods of drinking. Chronic Fatigue Syndrome involves persistent, disabling fatigue with other characteristic symptoms and needs clinical assessment rather than self-diagnosis.

Pause demanding tasks, drink fluids, eat a balanced meal and get daylight and gentle movement if you feel steady. Keep a consistent bedtime and avoid alcohol as a way to induce sleep. Review any new medicines with a pharmacist or clinician, but do not stop prescribed treatment suddenly. Write down sleep, meals, fluids, alcohol, mood, illness symptoms and when the tiredness appears. Do not drive or operate machinery if you might nod off. Book an appointment when fatigue is unexplained, recurring or affecting work, study or daily care.

Seek emergency help for sudden tiredness with chest pain, severe breathlessness, fainting, confusion, new weakness, trouble speaking, a severe headache or inability to stay awake. Get prompt medical advice for black stools, unusual bleeding, persistent vomiting, marked thirst with frequent urination, or fatigue that is rapidly worsening. Arrange assessment for ongoing tiredness with weight change, fever, swollen glands or significant mood changes.

Could sleep, mood, hydration, alcohol, infection, anaemia or another condition explain my fatigue? Should I review medicines or have blood and urine tests? What changes would make this urgent?