Causes of unexplained weight loss

Weight can fall when you eat less, absorb fewer nutrients, use more energy, or lose fluid. Dental problems, nausea, medication effects, depression and ongoing stress can reduce intake. Diarrhoea, abdominal pain or bloating may suggest a digestive condition such as coeliac disease or Crohn's disease. Increased thirst and urination can occur with diabetes, while heat intolerance, tremor or a racing heartbeat can accompany hyperthyroidism. Persistent fever, cough or night sweats require assessment for infection, including tuberculosis or HIV infection.

Record your weight trend, appetite, meals, bowel symptoms, thirst, medicines and emotional wellbeing. Book a clinical review if the loss is continuing, unplanned or accompanied by other symptoms. A clinician may examine you and choose blood, urine or imaging tests according to the pattern. Continue nourishing meals and fluids if you can, but avoid relying on supplements to mask a cause. Mention any restrictive eating, swallowing difficulty or access to food.

Seek prompt medical advice for ongoing loss, persistent diarrhoea or vomiting, difficulty swallowing, blood in stool, prolonged fever, drenching night sweats, marked thirst or severe low mood. Urgent care is needed for confusion, fainting, severe dehydration, intense abdominal pain or inability to keep fluids down. Weight loss alone does not identify one diagnosis; the accompanying pattern guides assessment.

What pattern in my symptoms is most useful to investigate? Could medicines, mood, digestion, thyroid or blood sugar be involved? Which tests are appropriate now? How can I maintain nutrition safely while we look for the cause?