Dr Charles Taïeb, a dermatologist at Necker University Hospital in Paris and a study author, said clinicians had previously had little beyond anecdotal reports of nail changes during GLP-1 treatment. He said the results showed an association, while warning that a problem arising during treatment cannot automatically be attributed to the medication.
Researchers assessed 575 people taking GLP-1 medicines against 1,329 people with type 2 diabetes, obesity or both who had never used the drugs. The participants were recruited in France, the United States, Brazil and Mexico, and medication users had been taking them for an average of 18.5 months.
The medicines included Ozempic, Wegovy, Mounjaro, Zepbound, Victoza and Trulicity. The findings were presented at the European Academy of Dermatology and Venereology (EADV) Congress 2026.
Nail detachment, where a fingernail separates from the tissue beneath it, was reported by 39% of GLP-1 users and 9% of people who had never taken the drugs. GLP-1 users were more than four times as likely to report the condition.
Overall, 66% of users reported at least one nail disorder, compared with 53% of the control group. Nail discoloration was reported by 46% of users and 17% of nonusers.
The gap persisted when researchers adjusted for weight loss. After also accounting for pre-existing skin conditions and nutritional deficiencies, nail detachment and discoloration remained approximately two to three times more common among GLP-1 users.
The hair and scalp results also differed between the groups. Half of GLP-1 users reported unusual hair loss, compared with 34% of nonusers. Reduced hair volume or density affected 42% of users and 19% of the control group, while 26% of users reported hair loss beginning after treatment started, compared with 12% of nonusers.
Scalp redness was approximately three times more frequent among GLP-1 users. Dr Bruno Halioua, a study author, said the scalp changes could reflect inflammation as well as the shedding commonly seen after rapid weight loss.
Researchers are planning long-term clinical trials to follow side effects from the first dose. The studies presented so far have not undergone formal peer review.
Experts said patients should seek advice from a medical professional before stopping medication. Research conducted by University College London estimated that 1.6 million adults in the UK use, or have previously used, weight loss drugs.
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