What causes unexplained weight loss?

Weight may fall when the body takes in fewer calories, absorbs less nutrition, or uses more energy during illness. Mouth pain, difficulty swallowing, nausea, diarrhoea, dental problems, depression, and medicine side effects can all reduce intake. Cancer cachexia is a complex process involving inflammation, muscle loss, appetite changes, and altered metabolism. Weight loss can accompany cancers such as bowel, lung, oesophageal, blood, or lymphoma conditions, but it does not identify cancer on its own.

Arrange a clinical review if weight is falling without a planned change. Bring a list of medicines, eating changes, bowel symptoms, swallowing difficulties, pain, stress, and recent infections. Your clinician may examine you and request blood tests, scans, or digestive investigations according to the pattern. A dietitian can suggest nourishing foods, texture changes, or symptom support; do not start restrictive diets while the cause is being investigated.

Seek prompt medical care for ongoing loss with trouble swallowing, repeated vomiting, blood in stool or vomit, persistent abdominal or chest pain, a new lump, prolonged fever, drenching sweats, or marked fatigue. Seek urgent help for severe dehydration, fainting, confusion, or inability to keep fluids down. The urgency depends on the symptoms alongside the weight change, not on weight loss alone.

What could explain my change in weight and appetite? Do I need blood tests or imaging? Could a medicine, swallowing issue, or digestive problem be contributing? Would a dietitian help? Which symptoms should make me seek urgent care?