Weight loss drugs have been linked to hair loss, a new study has claimed.
People on GLP-1 agonist drugs, such as Mounjaro, Ozempic and Wegovy, have been reporting hair loss to regulators and a new study on around 50,000 people appears to support the link.
GLP-1s are primarily used to treat diabetes and obesity by mimicking hormones to regulate blood sugar and reduce appetite.
Experts used data to compare rates of alopecia hair loss in adults using GLP-1s to manage diabetes with those on other drugs.
The team from the University of Pennsylvania Health System noted that regulators in the US have been informed of the link between the drugs and hair loss, particularly for semaglutide (Wegovy and Ozempic) and tirzepatide (Mounjaro).
So far in 2026, the UK Medicines and Healthcare products Regulatory Agency (MHRA) has received 399 reports of hair loss relating to tirzepatide, alongside 541 last year.
It has also received 148 reports of hair loss linked to semaglutide, alongside 164 reports last year.
For the new study, the team looked at people with type 2 diabetes on GLP-1 receptor agonists or other types of diabetes drugs known as SGLT-2 inhibitors, or DPP-4 inhibitors.
In total, 12,004 patients using GLP-1s were compared with 15,221 using SGLT-2 inhibitors and a further 11,964 GLP-1 users were compared with 11,233 DPP-4 inhibitor users.
After adjusting for factors that could influence the results, such as age and weight, researchers found using GLP-1 drugs were associated with a 37% higher risk of alopecia than use of SGLT-2 inhibitors.
GLP-1s were also linked to a 68% higher risk of hair loss than use of DPP-4 inhibitors.
Further analysis suggested the link related to non-scarring alopecia (where hair follicles remain intact, leaving the potential for hair to regrow).
The researchers, including from the University of Pennsylvania in the US, wrote in the British Medical Journal (BMJ): “Case reports and analyses of the US Food and Drug Administration (FDA)’s Adverse Event Reporting System have described occurrences of hair loss following initiation of a GLP-1 receptor agonist, particularly semaglutide (Wegovy and Ozempic) and tirzepatide (Mounjaro).
“In response, the FDA has indicated that it is evaluating this potential safety signal.
“Although hair loss does not typically result in physical harm, it may have significant psychosocial consequences, affecting self-esteem, quality of life, and adherence to treatment.”
On the reasons why people may suffer hair loss while on the drugs, the team said the “most likely mechanism” relates to weight loss and “reduced caloric intake”, though more research is needed.
They said restricting calories may “contribute to physiological stress and micronutrient deficiencies (for example, iron, zinc, biotin), which can disrupt the hair growth cycle”.
Other factors may include the “metabolic, hormonal, and immunological effects attributed to GLP-1 receptor agonists that may influence hair follicle growth and cycling”.
For example, GLP-1 receptor agonists have been associated with changes in thyroid function, and delayed gastric emptying may alter the absorption of orally administered drugs, including thyroid hormone or sex hormone therapies, they said.
“Such changes could influence hair growth through endocrine mechanisms, particularly in individuals with underlying hormonal conditions.”
The team concluded: “Our findings extend previous anecdotal safety signals and provide more systematic evidence to inform clinical awareness of this potential adverse effect.”
On Wednesday it was revealed the drugs have also been linked to a fall in the number of people who are dependent on alcohol being admitted to hospital.
Studies suggest the medication could help curb alcohol consumption.
However, researchers in the US said the evidence “remains limited and mixed”.
