How common is unexplained weight gain in hypothyroidism?

Thyroid hormones help regulate energy use and many body processes. When levels are low, the body may use energy more slowly. Weight change may also reflect fluid shifts, constipation, lower activity, or changes in appetite. The amount of change differs between people.

Other conditions and medicines can cause similar symptoms. A blood test is usually needed to assess thyroid function, and the result is interpreted with your symptoms, medical history, and any treatment already in use.

Arrange a medical appointment if weight gain comes with persistent tiredness, cold intolerance, constipation, dry skin, hair changes, or a slower-than-usual heartbeat. Bring a list of medicines and note when symptoms began. If thyroid treatment is prescribed, take it exactly as directed and attend planned blood-test reviews.

Avoid taking thyroid products or supplements without advice. They can interfere with testing or treatment and may not address the actual cause of weight change.

Seek urgent care for severe drowsiness, confusion, difficulty breathing, chest pain, or fainting. Contact your clinician sooner if symptoms worsen quickly, you are pregnant, or you have a known thyroid condition and cannot take your medicine.

Ask which thyroid tests are suitable, whether another condition or medicine could explain the change, when results should be reviewed, and how progress will be monitored.