- Researchers found GLP-1 drugs were associated with up to a 68 per cent higher risk of hair loss than some other diabetes medicines.
- UK regulators have received more than 1,200 reports of hair loss linked to semaglutide and tirzepatide since last year.
- Experts say rapid weight loss may be the most likely explanation, but further research is needed.
Popular GLP-1 weight loss drugs such as Mounjaro, Ozempic and Wegovy are under fresh scrutiny after a major study found they may be linked to a higher risk of hair loss. The findings add to a growing number of reports already being reviewed by health regulators in both the UK and the US, although researchers say more evidence is needed before any direct link can be confirmed.
The study, published in the British Medical Journal (BMJ), analysed health records from around 50,000 adults and compared people taking GLP-1 receptor agonists with those using other medicines to manage type 2 diabetes. Researchers found that people using GLP-1 drugs had a 37 per cent higher risk of developing alopecia than those taking SGLT-2 inhibitors, while the risk was 68 per cent higher compared with people using DPP-4 inhibitors.
Patient reports are now backed by larger evidence
Researchers from the University of Pennsylvania examined data from the University's Health System, comparing 12,004 people taking GLP-1 medicines with 15,221 patients using SGLT-2 inhibitors. They also compared 11,964 GLP-1 users with 11,233 people taking DPP-4 inhibitors.
After accounting for factors such as age and body weight, the higher rates of hair loss remained consistent.
The researchers noted that similar concerns have already been reported to regulators. According to the study, the US Food and Drug Administration is continuing to evaluate hair loss as a potential safety signal, particularly for semaglutide, sold as Ozempic and Wegovy, and tirzepatide, marketed as Mounjaro.
The UK's Medicines and Healthcare Products Regulatory Agency (MHRA) has also received a growing number of reports. The regulator recorded around 400 reports of hair loss linked to tirzepatide during 2026, following 541 reports in 2025. It also received 148 reports involving semaglutide this year, after 164 reports were submitted last year.
Researchers say rapid weight loss may be the key factor
The researchers stressed that the findings show an association rather than proving the medicines directly cause hair loss. They suggested the most likely explanation is the rapid weight loss experienced by many people taking GLP-1 medicines.
According to the study, eating fewer calories during significant weight loss can place the body under physiological stress and contribute to deficiencies in nutrients such as iron, zinc and biotin, all of which are important for healthy hair growth. The medicines' metabolic, hormonal and immune-related effects may also influence the normal hair growth cycle, although the researchers said further studies are needed to better understand those mechanisms.
Writing in the BMJ, the researchers reportedly said hair loss may not cause physical harm, but it can have "significant psychosocial consequences", affecting self-esteem, quality of life and even whether people continue taking their medication, as quoted in a news report.
While the findings strengthen concerns that have been raised by patients and regulators, the researchers emphasised that more research is needed to determine whether the medicines themselves increase the risk of hair loss, or whether the effect is largely linked to the rapid weight loss that often accompanies treatment.
