Unexplained weight loss

Category: General & Whole-Body Symptoms · All general symptoms

What it can feel like

Unexplained weight loss means losing a noticeable amount of weight without trying — clothes becoming loose over a few months without any change in eating or activity. Because it is not explained by diet or exercise, clinicians always take it seriously and look for a cause.

Possible causes

A symptom can have many causes, and most are not serious. The lists below group conditions this symptom can be associated with — common causes first. They are possibilities to discuss with a clinician, not a diagnosis.

Common causes

Weight loss can be associated with stress, anxiety or low mood affecting appetite, with an overactive thyroid, with diabetes that is not yet controlled, and with long-term infections or recovery from illness.

Other possible causes

It can also be associated with conditions of the stomach and bowel that reduce absorption, with chronic lung, heart or kidney disease, and with cancers — which is why new unexplained weight loss should always be discussed with a clinician.

Red flags — when to seek help promptly

Weight loss with persistent fever, night sweats or swollen glands
Weight loss with blood in the stool, a persistent change in bowel habit or vomiting
Weight loss with a new lump anywhere in the body
Rapid weight loss with extreme thirst and passing lots of urine
Weight loss in someone who has lost interest in food entirely

What a clinician may do

A clinician will weigh you and compare with previous records, ask about appetite, bowels, mood and other symptoms, and examine you. Blood tests, urine tests and sometimes a chest X-ray are usual first steps; imaging or referral to a specialist depends on what is found.

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Frequently asked questions

How much weight loss matters?

Losing around 5% of your body weight over six to twelve months without trying is the level clinicians usually want to investigate. The trend matters more than any single weighing, so older weights from clinic records are useful.

Does weight loss always mean something serious?

No — stress, thyroid problems, diabetes and treatable bowel conditions are all common explanations. But because the list also includes serious causes, it should always be checked rather than watched indefinitely.

Related symptoms — General & Whole-Body Symptoms

Chills Excessive sweating Excessive thirst Fatigue Feeling cold all the time Feeling generally unwell (malaise)

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Please note: This page is educational information about a symptom. A symptom alone cannot diagnose any condition, and the causes listed here are possibilities, not a diagnosis. If you are worried about a symptom — especially one that is new, severe, getting worse or not going away — please see your own clinician, who can examine you and arrange tests. In an emergency, call your local emergency number.