The drug class includes semaglutide, sold under brand names such as Ozempic and Wegovy, and tirzepatide, sold as Mounjaro and Zepbound. Researchers found that adults with type 2 diabetes who used GLP-1 receptor agonists developed alopecia more often than patients taking two other common types of diabetes medication.

Although the relative increase was significant, the researchers emphasized that the absolute risk of hair loss remained low. Still, knowing about the possible side effect could help patients and clinicians make more informed treatment decisions together.

Hair Loss Reports Linked to Ozempic and Similar Drugs

Hair loss has previously been reported as a possible side effect of GLP-1 receptor agonists, particularly medications containing semaglutide or tirzepatide. However, there has been limited research directly comparing the risk among GLP-1 users with the risk among patients taking other diabetes treatments.

To investigate, researchers analyzed electronic health records from the University of Pennsylvania Health System (Penn Medicine). They compared alopecia rates among adults with type 2 diabetes who began treatment with GLP-1 receptor agonists, SGLT-2 inhibitors, or DPP-4 inhibitors.

The analysis covered patients treated between January 2019 and September 2024. One comparison included 12,004 people taking GLP-1 receptor agonists and 15,221 taking SGLT-2 inhibitors. A separate comparison included 11,964 GLP-1 users and 11,233 people taking DPP-4 inhibitors.

Researchers Accounted for Differences Between Patients

The groups differed in several important ways before the researchers adjusted the results.

Compared with people taking SGLT-2 inhibitors, GLP-1 users were younger (mean age 58 v 65), had a higher body mass index (36.2 v 32.3), and had lower rates of cardiovascular disease and chronic kidney disease.

A similar pattern appeared in the comparison with DPP-4 inhibitors. GLP-1 users were younger (mean age 58 v 67) and had a higher body mass index (36.2 v 31.3).

The researchers adjusted for factors that might affect the findings, including age, sex, ethnicity, pre-existing conditions, use of other medications, and body mass index.

GLP-1 Users Had Higher Alopecia Rates

After those adjustments, GLP-1 receptor agonist use was associated with a 37% higher risk of alopecia compared with SGLT-2 inhibitor use (6.91 v 5.04 per 1,000 person years).

The risk was 68% higher when GLP-1 users were compared with people taking DPP-4 inhibitors (6.53 v 3.89 per 1,000 person years).

Further analysis suggested that the connection was limited to non-scarring alopecia (where hair follicles remain intact, leaving the potential for regrowth). The risk of this form of hair loss was 53% higher among GLP-1 users than among SGLT-2 inhibitor users and 72% higher than among DPP-4 inhibitor users.

Rapid Weight Loss Could Affect the Hair Cycle

The study did not establish why GLP-1 drugs might be connected to hair loss. However, the authors pointed to several possible explanations.

Rapid weight loss is a well established cause of increased hair shedding. It may also contribute to iron or zinc deficiencies, both of which can interfere with the normal hair growth cycle. Hormonal changes related to weight loss or treatment could also play a role, although additional research will be needed to identify the underlying mechanisms.

Important Questions Remain

The researchers acknowledged several limitations. Available clinical records did not provide enough detail to determine the severity, extent, or duration of the alopecia. The team also could not assess whether hair grew back after patients stopped taking the medication.

In addition, the observational study cannot prove that GLP-1 drugs directly caused the hair loss. Other factors that were not measured could have affected the results.

Even so, the authors described the research as rigorous and noted that it used high quality data from a large and representative group of patients. The findings also remained consistent across additional analyses, supporting their reliability.

The researchers concluded: "Our findings extend previous anecdotal safety signals and provide more systematic evidence to inform clinical awareness of this potential adverse effect."