A FAERS analysis finds tirzepatide negatively associated with hair loss reporting

A study published March 26, 2026, in Diabetes/Metabolism Research and Reviews looked at reports of alopecia and reproductive or hormone-related adverse events tied to six GLP-1 receptor agonists in the FDA's Adverse Event Reporting System, or FAERS ^[1]. The analysis covered reports filed from the second quarter of 2022 through the second quarter of 2025, a window chosen to start after tirzepatide's approval so all six drugs could be compared over the same period ^[1].

Using adjusted reporting odds ratios, or aROR, which try to account for age, sex, indication, reporting country, and who filed the report, the researchers found semaglutide positively associated with alopecia, with an aROR of 1.23 ^[1]. Tirzepatide, by contrast, was negatively associated with several reproductive outcomes, and the summary of this development places its overall alopecia-related aROR at 0.78, meaning reports of hair loss were less common for tirzepatide than would be expected compared with other drugs in the dataset ^[1]. The study also found semaglutide linked to reproductive or hormonal signals, including a much larger aROR of 6.59 for polycystic ovary syndrome reports, while dulaglutide and tirzepatide showed lower reporting for outcomes such as dysmenorrhea, amenorrhea, and heavy menstrual bleeding ^[1].

The study identified 1,276 alopecia-related cases and 759 reproductive or endocrine-related cases across the six drugs during the study period, after cleaning FAERS data to remove duplicate case reports and keeping only cases where the GLP-1 drug was listed as the primary suspect ^[1]. The authors ran sensitivity checks using positive and negative control drugs, which they say supported the consistency of their findings ^[1].

This result stands apart from other pharmacovigilance work that has grouped tirzepatide with semaglutide as the two GLP-1 drugs carrying the strongest hair-loss signals, according to the development summary describing this contradiction. The paper itself does not resolve why its tirzepatide finding runs opposite to that pattern, and the provided source material does not include a discussion section explaining the discrepancy. The study's introduction does note that earlier real-world work, including a large multicenter cohort study and accumulating case reports, has linked GLP-1 drugs broadly to hair loss, particularly telogen effluvium and androgenic alopecia ^[1].

Why it matters for patients

FAERS is a spontaneous reporting system, not a controlled trial, so a negative or positive association in this database does not prove a drug causes or prevents hair loss. Reporting patterns can be shaped by how doctors and patients notice and report side effects, not just by biology. For someone taking Mounjaro or Zepbound (tirzepatide) or Ozempic, Wegovy, or Rybelsus (semaglutide) and weighing hair loss as a possible side effect, this study adds a data point that conflicts with other signals rather than settling the question. Patients who have experienced hair thinning while on either drug class may find that the scientific record on this specific symptom is still inconsistent between studies using the same kind of database.

The conflicting results also underscore a broader limitation of pharmacovigilance research: two studies can use similar FAERS data but reach different conclusions depending on the time window, adjustment methods, and case definitions used. The authors of this study frame their findings as evidence for "agent-specific differences" in safety profiles that could support more personalized drug selection, but they also call for continued pharmacovigilance, language that signals the picture is not yet complete ^[1].

What happens next

The source material provided does not describe planned follow-up studies, FDA action, or a timeline for reconciling this finding with other analyses that have linked tirzepatide to hair loss. It is not yet known when or whether additional research will resolve the disagreement between this study and prior work on tirzepatide and alopecia reporting.