In the studies the FDA reviewed before approving Wegovy, about 1 in 33 people on the peptide had extra hair shedding. In the placebo group, the rate was about 1 in 100.

So the peptide does add some hair shedding. A real difference, but a small one. The same pattern showed up in the tirzepatide research behind Mounjaro and Zepbound.

The hair loss isn't caused by the peptide acting on hair. It's caused by the fast weight loss the peptide produces. The same shedding pattern shows up in any rapid weight loss: bariatric surgery, very-low-calorie diets, illness.

Dermatologists have a name for it: telogen effluvium, the synchronized shedding phase the body shifts into about two to four months after a metabolic shock. The hair grows back once weight stabilizes, usually over the next several months.