Can I use weight loss injections (known as ’GLP-1’ medications) if I have a thyroid condition?

Weight loss injections and thyroid conditions

Medications are available to help people with obesity or who are overweight lose weight. Some of the most commonly used are called ‘Glucagon-like peptide-1 receptor agonists (GLP1-RA)’ or 'GLP-1s' for short. These medications are used to treat diabetes and to support weight loss in people with obesity or who are overweight with weight-related health problems. In all groups of patients, they should be used alongside a reduced-calorie diet and regular exercise.

In the UK, there are three licensed GLP1-RA medications: Semaglutide (also called Wegovy, Ozempic and Rybelsus), tirzepatide (this medication also activates the GIP receptor and is Mounjaro) and liraglutide (sold under various brand names). You should only use weight loss injections if they have been prescribed for you by a healthcare professional after a full discussion about the benefits and risks of these treatments based on your individual circumstances.

There are no specific reasons why people with benign (not cancerous) thyroid conditions should not use weight loss injections, although it may be advisable to avoid them until your thyroid hormone levels are normal (euthyroid).

Studies using some GLP1-RA medications in rats have shown they may cause a rare thyroid cancer called medullary thyroid cancer. Studies using weight loss injections in the short to medium term in humans have not shown that their use is associated with an increased risk of thyroid cancer.  

GLP1-RA medications should not be used if there is a personal or family history of a thyroid cancer called medullary thyroid carcinoma (MTC). This also applies to anyone with a personal or family history of Multiple Endocrine Neoplasia Syndrome type 2 (MEN 2), a condition in which almost 100% of people develop MTC before the age of 40.

Patients with a history of other types of thyroid cancer should discuss the potential risks and benefits with their doctor before starting treatment; however, are often able to take these medications on completion of their thyroid cancer treatment.

If you are taking levothyroxine to treat hypothyroidism (underactive thyroid), you may need to have your thyroid function checked approximately 2-3 months following substantial weight loss. This is to establish whether your levothyroxine dose needs adjusting. Patients on antithyroid medications (carbimazole, propylthiouracil) may need additional monitoring and it would be sensible to let your endocrinologist and GP know that you are taking or thinking about taking weight loss injections.

Please consult your healthcare professional, the manufacturer’s patient information leaflet and The Medicines and Healthcare products Regulatory Agency (MHRA) for up-to-date information about benefits and risks and how to use these medicines safely.

Guidance updated April 2026

This is a rapidly developing area; therefore, please consult a healthcare professional for the latest information and guidance.

Further information

Medicines and Healthcare products Regulatory Agency (MHRA)

Yellow Card reporting site