Unexplained weight loss

Unexplained weight loss is losing a noticeable amount of weight – officially, 5% of your body weight - without dieting or taking more exercise.

By Wallace Health I Medically reviewed by Adrian Roberts.
Page last reviewed: October 2018 I Next review due: October 2023


Unexplained weight loss, which is sometimes called unintentional weight loss, can affect anyone at any age. If you’re older, any unexplained or sudden weight loss, no matter how little, may be significant.

Unexplained weight loss can be triggered by stress but can also be a symptom of an underlying health condition. Sudden, noticeable, unexplained weight loss should always be checked out by your GP so any underlying causes can be treated.

Causes of unexplained weight loss

Unexplained weight loss is often caused by a stressful event, such as bereavement, redundancy or moving to a new house.

It can be a symptom of many different health conditions, including:

  • Depression or anxiety
  • Eating disorders such as anorexia and bulimia
  • Overactive thyroid (hyperthyroidism) – a condition which is 10 times more common in women than men
  • Malnutrition - caused by poor diet, dental problems or swallowing problems (dysphagia)
  • Cancer
  • Type 1 diabetes
  • Undiagnosed type 2 diabetes – diabetes weight loss is more likely if you’re over the age or 40
  • Ovarian cancer
  • Diarrhoea

Occasionally, unexplained weight loss can be a symptom of:

Talk to your doctor if you’re concerned about symptoms

You can book an appointment with a Spire private GP today.

Getting a diagnosis for unexplained weight loss

To diagnose the cause of your unexplained weight loss, your GP will discuss your weight and general health. They’ll also ask if you’ve noticed any other symptoms, perhaps including:

  • Hair loss
  • Tiredness
  • stomach problems
  • Increased thirst

Your GP may also examine you, weigh you and test your blood. This should enable them to identify any causes of weight loss and arrange the necessary treatment for you.

In some cases, your GP may suggest waiting for a few months before undergoing further tests.

Your GP may refer you to a consultant – such as a gastroenterologist, geriatrician or endocrinologist – for further assessment.

Treatments for unexplained weight loss

If stress is the reason for your unexplained weight loss, your weight should return to normal as your stress reduces. If stress is making life difficult for you, your GP or consultant may refer you to a counsellor.

If an eating disorder is at the root of your unexplained weight loss, your GP will arrange the relevant treatment.

If an underlying condition’s responsible for your unexplained weight loss, the treatment your doctor recommends will depend on your diagnosis.

Your doctor may also refer you to a dietitian. A dietitian will give you nutritional advice and, if required, a special diet to prevent further weight loss.