Popular diabetes and weight loss medicines including Mounjaro, Ozempic and Wegovy may be linked to a higher risk of hair loss, according to new research involving nearly 50,000 patients.
The study found that people taking GLP-1 receptor agonists were more likely to develop alopecia than patients using other classes of diabetes medicines. The findings add to reports already submitted to drug regulators about hair loss among people taking semaglutide and tirzepatide.
Researchers from the University of Pennsylvania examined electronic health records from adults with type 2 diabetes. They compared patients taking GLP-1 drugs with those using SGLT-2 inhibitors and DPP-4 inhibitors.
One comparison included 12,004 GLP-1 users and 15,221 patients taking SGLT-2 inhibitors. A second involved 11,964 GLP-1 users and 11,233 people using DPP-4 inhibitors.
After accounting for factors including age and body weight, the researchers found that GLP-1 use was associated with a 37 per cent higher risk of alopecia compared with SGLT-2 inhibitors. The risk was 68 per cent higher when GLP-1 drugs were compared with DPP-4 inhibitors.
The analysis suggested that the hair loss was mainly non-scarring alopecia, meaning the hair follicles remain intact and hair may regrow.
Regulators have already received reports of hair loss linked to the medicines. In the UK, the Medicines and Healthcare products Regulatory Agency has received 399 reports related to tirzepatide so far in 2026, following 541 reports last year. It has also received 148 reports associated with semaglutide this year, compared with 164 in 2025.
The researchers said the most likely explanation could involve rapid weight loss and reduced calorie intake. Significant dietary restriction can place the body under physiological stress and may lead to shortages of nutrients such as iron, zinc and biotin, which are important for healthy hair growth.
The researchers also said the medicines could affect hair through metabolic, hormonal and immune-related changes. GLP-1 drugs have been linked to changes in thyroid function, while delayed stomach emptying may affect how some oral medicines are absorbed.
Writing in the British Medical Journal, the researchers said hair loss is generally not physically harmful but can affect self-esteem, quality of life and a person’s willingness to continue treatment.
They said the findings provide more systematic evidence of a possible side effect previously identified through individual reports and regulator safety data.
The researchers stressed that further work is needed to understand the exact biological mechanisms behind the association and determine how factors such as the amount and speed of weight loss may influence the risk.
