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Why does GLP-1 cause hair loss

You are dealing with a symptom and want to know if it is expected.

Reference and calculator, not medical advice. This page explains how something works; it does not tell you what to take. Last reviewed August 2026.

The honest answer is that the labels do not explain the mechanism. They state an association and stop. Both Wegovy and Zepbound use the identical formulation: hair loss reactions "were associated with weight reduction". No pathway, no biology, no further claim.

That restraint is meaningful rather than evasive. The manufacturers had the trial data and the regulatory incentive to characterise this precisely, and what they were willing to put in a legally binding document was an association with weight loss. Every mechanistic explanation you will read elsewhere is an inference on top of that sentence, not something the evidence in these documents establishes.

The clearest number in any of the labels

Wegovy trials, women only, same measurement across three arms. Rate rises with dose while the label attributes the effect to weight reduction rather than to the drug.

Men in the same trials: 0% · 0% · 0.2%. The sex difference is larger than the dose difference, which is the part almost no summary of this topic mentions.

Why the women’s figure for 2.4 mg differs from the table above: these three arms come from the 7.2 mg trial programme, while the other figure is pooled from three earlier weight-management trials. Both are in the label and both report 3.3% overall at 2.4 mg — the sex split differs because the trial populations do. Both are shown rather than picking the more striking one.

What the data does support is a pattern. The rate rises with dose, the rate is far higher in women, and the rate is not zero in people taking placebo. A mechanism that explains all three would need to account for a strong sex effect and a background level in untreated people — which is a harder problem than most confident explanations acknowledge.

What each label actually reports

Incidence figures come from the adverse-reaction sections of the prescribing information. The two weight-management products report trial data; the diabetes products list alopecia only as a postmarketing report.

ProductReported inWomenMen
Wegovy SemaglutideClinical trials4%0.9%
Zepbound TirzepatideClinical trials7.1%0.5%
Ozempic SemaglutidePostmarketing reports onlyno denominatorno denominator
Mounjaro TirzepatidePostmarketing reports onlyno denominatorno denominator
Rybelsus Semaglutide (oral)Postmarketing reports onlyno denominatorno denominator
Saxenda LiraglutidePostmarketing reports onlyno denominatorno denominator
Trulicity DulaglutidePostmarketing reports onlyno denominatorno denominator

A postmarketing entry means the reaction has been reported after approval but the label gives no rate, because spontaneous reports have no denominator. It is not evidence that the rate is lower — only that it was not measured. Every figure above is checked against the label linked at the foot of this page.

Common questions

Is it a nutrient deficiency?
The labels do not say so, and the trials did not report nutrient status alongside these reactions. It is a plausible-sounding idea with no support in these documents either way. A blood test answers it for you personally in a way that speculation cannot.
Why would higher doses matter if it is the weight loss?
Because higher doses also produce more weight loss. The dose-response curve is consistent with both readings, and the trials were not designed to separate them. That ambiguity is real and worth stating plainly.
Why do the diabetes versions not report a rate?
They list alopecia only as a postmarketing report, with no denominator. Their trials were designed around glycaemic outcomes in populations losing much less weight, which is consistent with the labels attributing the effect to weight reduction — but consistency is not proof.

Sources and last review

This page is general reference rather than a dosing table, so it quotes no figures from a label. Nothing here is reviewed by a clinician, and this site does not employ one — which is exactly why what I do publish stays traceable to its source.

Transcribed from the labels above and checked by me — Gavin, who builds this site, takes a GLP-1, and is not a clinician. Last reviewed August 2026. Found an error? [email protected] — I treat corrections as bugs. How this site is built and funded.

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