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Unintentional weight loss

Sudden, noticeable weight loss can happen after a stressful event. But it can also be a sign of a serious illness.


It's normal to lose weight after the stress of changing jobs, divorce, redundancy or bereavement.

Your weight often returns to normal when you start to feel better. You may need time to grieve or get used to the change. You can get counselling and support to help with this.

Eating disorder

A big weight loss can be the result of an eating disorder, such as anorexia or bulimia.

If you think you have an eating disorder, talk to someone you trust and think about contacting your GP.

Bodywhys provides information and support about eating disorders.

Non-urgent advice: Contact your GP if:

  • you do not know the cause of your weight loss or
  • you did not lose the weight through dieting or exercising.

You may have an illness that needs treatment.

When weight loss is a concern

Your body weight can change often. But the continued, unintentional loss of more than 5% of your weight over 6 to 12 months is often a cause for concern.

Losing this much weight can be a sign of malnutrition. This is where a person's diet does not have the right amount of nutrients.

Contact your GP if you have other symptoms, such as:

  • tiredness
  • loss of appetite
  • a change in your toilet habits
  • an increase in illnesses or infections

Causes of unexpected weight loss

Unintentional weight loss does not always have an underlying cause, such as a stressful event or eating disorder.

But other common causes include:

Less common causes of unexpected weight loss

Less often, unexpected weight loss may be the result of:

  • the side effects of certain medications
  • drug misuse or alcohol misuse
  • heart, kidney, lung or liver disease
  • a problem with the glands that secrete hormones – such as Addison's disease or undiagnosed diabetes
  • a long-term inflammatory condition, such as rheumatoid arthritis or lupus
  • dental problems – such as losing teeth, having new orthodontics (such as braces) or mouth ulcers
  • a condition that causes dysphagia (swallowing problems)
  • a problem with the gut, such as a stomach ulcer, Crohn's disease, ulcerative colitis or coeliac disease
  • a bacterial, viral or parasitic infection, such as tuberculosis (TB), HIV and AIDS, or persistent gastroenteritis
  • dementia, people with dementia may be unable to tell you their eating needs

Content supplied by the NHS and adapted for Ireland by the HSE

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 25 March 2021
Next review due: 25 March 2024