What should you know about unexplained weight loss fatigue?

Fatigue can follow poor sleep, stress, low mood, under-eating, or an illness. When it occurs with unplanned weight loss, possible causes include coeliac disease, Crohn's disease, hyperthyroidism, depression, tuberculosis, HIV infection, or type 1 or type 2 diabetes. Anaemia and medicine effects may also be relevant even when they are not the only explanation. The pattern is not specific: the combination does not identify one condition without a history and examination.

Arrange a primary-care review, particularly if symptoms are continuing or affecting work, study, movement, or eating. Record your appetite, sleep, mood, thirst, urination, bowel changes, fever, pain, and the timing of weight change. Take your medicine and supplement list. Try regular meals, fluids, and manageable activity without pushing through marked exhaustion. A clinician may consider an examination and targeted tests based on your pattern.

Seek urgent help for fainting, confusion, severe weakness, inability to keep fluids down, breathing difficulty, severe abdominal pain, or signs of dehydration. Weight loss and fatigue with marked thirst and frequent urination, persistent fever, night sweats, or rapidly worsening illness needs prompt medical attention.

Could the fatigue and weight loss share one cause? Should we check blood count, thyroid function, blood sugar, nutrition, infection, or digestion? How should I pace activity and maintain food and fluid intake while waiting for results?