GLP-1 Weight Loss Drugs Linked to Hair Loss Risk, BMJ Study Finds July 24

A new study published in The BMJ on July 23 found that adults taking GLP-1 receptor agonists like semaglutide and tirzepatide face a significantly higher risk of hair loss than patients on other diabetes medications. Researchers at the University of Pennsylvania analysed 50,000 patient records and found GLP-1 users had a 37% higher risk of alopecia versus SGLT-2 inhibitors and 68% higher versus DPP-4 inhibitors. The absolute risk remains low, affecting 3-9 people per 1,000 annually, but the finding matters for investors in Eli Lilly (LLY) and Novo Nordisk (NVO), which dominate the GLP-1 market.

What the study found

Researchers compared GLP-1 users with patients taking SGLT-2 and DPP-4 inhibitors between January 2019 and September 2024. GLP-1 users showed 37% higher alopecia risk versus SGLT-2 inhibitors and 68% higher versus DPP-4 inhibitors. The hair loss was primarily non-scarring, meaning follicles remained intact and regrowth was possible. Most observed cases were reversible, according to the study authors.

Why GLP-1 drugs may trigger hair loss

The researchers believe rapid weight loss and reduced calorie intake are the main culprits. These trigger telogen effluvium, a temporary shedding phase. Nutritional deficiencies in iron, zinc and biotin from caloric restriction may also play a role. Hormonal and metabolic changes caused by the drugs could contribute, though further research is needed to clarify the exact mechanisms.

Real-world reports and regulatory data

The UK’s Medicines and Healthcare products Regulatory Agency received 940 hair loss reports linked to tirzepatide since January 2025 and 312 reports involving semaglutide. Researchers emphasised that the absolute risk remained low, but the findings provide stronger evidence than previous anecdotal reports. The effect appeared strongest around one year after starting treatment, particularly in women.

What this means for investors

With Meyka grading LLY a B+ and NVO a B, and both stocks facing potential patient adherence concerns, the data cuts both ways. LLY trades at a 41.9x PE ratio with 11 analyst Buy ratings, while NVO trades at 11.6x PE with one Buy and two Hold ratings. Patient satisfaction and treatment continuation could be affected if hair loss becomes a widely known side effect, though the low absolute risk may limit commercial impact.

Final Thoughts

The BMJ study confirms a real but low-risk link between GLP-1 drugs and hair loss. For LLY and NVO investors, the key question is whether awareness of this side effect will deter patients or simply shift them to dose adjustments and nutritional support. The reversible nature of most cases may contain reputational damage.

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The content shared by Meyka AI PTY LTD is solely for research and informational purposes.  Meyka is not a financial advisory service, and the information provided should not be considered investment or trading advice.