Unintentional Weight Loss: Why It Matters
Losing weight without trying can have many causes, from stress to medical conditions. Learn the common reasons, what a clinician may ask, and why to get it checked.
Content last updated . This page has not been medically reviewed.
Safety first
Losing weight when you are not trying to lose weight is a reason to see a doctor. NHS says unintentional weight loss can be a sign of stress or a serious illness and advises seeing a GP just in case; it says that if you keep losing weight without changing your diet or exercise routine, you should see a GP, and as soon as possible if you also have other symptoms, because the earlier the cause is found, the sooner it can be treated. [1] If you think the loss could be related to an eating disorder, see Eating disorders and disordered eating for urgent help options.What counts as significant
MedlinePlus defines unintentional weight loss as a loss of 10 pounds (4.5 kg) or 5% of your normal body weight over 6 to 12 months or less without knowing the reason, and advises contacting a provider in that situation or if you have other symptoms. [2] Weight loss that is intended, for example through a program or medicine, is covered on other pages such as Healthy weight basics.Common causes
The sources list many possible causes. This does not mean any of them applies to you.| Area | Examples from the sources |
|---|---|
| Stress and mental health | Stressful events such as divorce, job loss or bereavement; depression, anxiety, eating disorders and obsessive compulsive disorder. [1] |
| Digestion | Celiac disease, inflammatory bowel disease; long-lasting infections; overuse of laxatives; removal of part of the small intestine. [1][2] |
| Hormones and metabolism | Overactive thyroid; type 1 diabetes; undiagnosed diabetes. [1][2] |
| Heart and other chronic illness | Heart failure; chronic illnesses such as COPD or Parkinson disease. [1][2] |
| Nutrition and appetite | Poor nutrition or lack of appetite, though weight can fall even when diet and appetite have not changed. [1] |
| Medicines | Side effects of some medicines such as levothyroxine; MedlinePlus also lists chemotherapy and thyroid medicines. [1][2] |
| Substances | MedlinePlus lists drug use such as amphetamines and cocaine. [2] |
| Cancer | Sometimes weight loss and loss of appetite can be caused by cancer, which is why it is important to get it checked. [1] |
NIDDK also notes that people with type 1 diabetes may have unexplained weight loss along with increased urination and thirst. [3] See Celiac disease and gluten-related symptoms, Thyroid problems and fatigue and Appetite changes and unintended weight loss in older adults.
What to expect at a visit
NHS says a GP will ask about your health and may arrange tests or scans, then advise on ways to help, treat any condition causing it, or refer you to a specialist. [1] MedlinePlus says a provider will do a physical exam, check your weight and ask about things such as how much weight you lost, how fast, eating and exercise changes, stress, vomiting, medicines and mood. [2] Bring a list of your medicines and supplements.What to avoid
- Getting the cause checked comes first. The sources advise a visit to a clinician, not self-treatment with supplements, weight-gain products or restrictive diets. [1][2]
- Ignoring it because the change feels welcome. NHS advises getting it checked when you are losing weight without trying. [1]
When to get help
See a clinician if you have lost weight without trying, especially if you have other symptoms, are losing weight over months, or are unsure why. [1][2]Frequently asked questions
How much weight loss is too much?
MedlinePlus uses 10 pounds (4.5 kg) or 5% of normal body weight over 6 to 12 months or less, without a known reason, as a point to contact a provider, and also advises contacting one if you have other symptoms along with the weight loss. [2]
Can stress cause weight loss?
Yes, NHS lists stressful events and mental health conditions among causes. [1] It is still sensible to have it checked.
Is unexplained weight loss always serious?
No, but NHS says it can be a sign of serious illness, so a check is advised. [1]
References
- NHS. Unintentional weight loss. Read 2026-10-22.
- MedlinePlus. Weight loss - unintentional. Read 2026-10-22.
- NIDDK. Symptoms and causes of diabetes. Read 2026-10-22.