Ask whether GLP-1 medicines work differently in men and women and you get two confident answers online: "women lose more" and "it makes no difference". Both are in the official record, and they are not contradictions — they answer different questions. This page reads the labels, the posted trial data and the one meta-analysis built to answer the question, as of 28 September 2026.
What the labels say
The two big weight labels use the same wording:
- Zepbound: "A reduction in body weight was observed with ZEPBOUND irrespective of age, sex, race, ethnicity, baseline BMI, and glycemic status." Sex does "not have a clinically relevant effect on the PK of tirzepatide."
- Wegovy: weight reduction "irrespective of age, sex, race, ethnicity"; "no clinically significant differences in semaglutide pharmacokinetics were observed based on … sex".
"Irrespective of sex" means both sexes lost weight compared with placebo. It does not mean they lost the same amount. And the pharmacokinetic sentence means the drug reaches similar levels in the blood — so if women lose more, it is not simply because the same dose is a bigger dose for them.
Do women lose more? The evidence
The meta-analysis. A 2025 systematic review searched for randomised trials that reported weight change separately by sex and found 14, covering dulaglutide, exenatide, liraglutide, semaglutide and retatrutide (J Diabetes 2025):
| Finding | Result |
|---|---|
| Women vs men, weight lost | 1.04 kg more (95% CI 0.70–1.38) |
| Women vs men, % of body weight | 1.69 points more (95% CI 0.78–2.61) |
| Gap in trials of weight-loss indications | 4.21 kg |
| Gap by drug | significant for dulaglutide and semaglutide; none found for exenatide |
| Pattern | the more weight a drug produced, the larger the sex gap |
Tirzepatide was not among the drugs in that analysis.
A real-world cohort for tirzepatide. Mayo Clinic followed 1,039 adults who started tirzepatide between June 2022 and May 2024 and stayed on it at least 12 months (Obesity 2026). At 15 months, women had lost 15.1% against 10.7% for men. In the adjusted analysis, female sex, not having type 2 diabetes, no prior obesity medicine and a higher dose were each associated with more weight loss; age was not. It is a single-centre, retrospective study of people who stayed on the drug, so it describes that group, not everyone who starts.
Women by life stage. A post-hoc analysis of women in SURMOUNT-1 found similar losses on tirzepatide before, around and after menopause (26%, 23% and 23% against 2–3% on placebo; Obesity 2025). The menopause question in more depth is on GLP-1 and menopause.
Who the trials enrolled — an original count
The balance of men and women in a trial decides how confidently its average applies to each. We read the baseline tables posted on ClinicalTrials.gov for eight pivotal trials:
| Trial | Drug | What it tested | Women | Men | % women |
|---|---|---|---|---|---|
| OASIS 4 | Wegovy pill | weight | 242 | 65 | 78.8% |
| SCALE Obesity | Saxenda | weight | 2,928 | 803 | 78.5% |
| STEP 1 | Wegovy | weight | 1,453 | 508 | 74.1% |
| SURMOUNT-1 | Zepbound | weight | 1,714 | 825 | 67.5% |
| SURMOUNT-5 | Zepbound vs Wegovy | weight | 485 | 265 | 64.7% |
| ATTAIN-1 | Foundayo | weight | 2,009 | 1,118 | 64.2% |
| SURMOUNT-OSA | Zepbound | sleep apnoea | 142 | 327 | 30.3% |
| SELECT | Wegovy | heart attacks, strokes | 4,872 | 12,732 | 27.7% |
The pattern is clean: every weight trial was majority women, and both outcome trials were majority men. The headline weight-loss percentages on every label are therefore mostly women's results, while the heart and sleep-apnoea indications rest mostly on men. The labels report that the heart benefit in SELECT "was not impacted by … sex", but a subgroup of 4,872 women is where that sentence comes from.
Side effects by sex
The labels publish sex-split figures for only a few reactions:
| Reaction | Drug | Women | Men | Placebo women / men |
|---|---|---|---|---|
| Hair loss | Zepbound (pooled trials 1–2) | 7.1% | 0.5% | 1.3% / 0% |
| Hair loss | Wegovy 2.4 mg (pooled studies 2–4) | 4% | 0.9% | 2% / 0% |
| Hair loss | Wegovy 7.2 mg | 8.4% | 0.2% | 1.5% / 0% |
| Hip and pelvis fracture | Wegovy (SELECT) | 1.0% (24/2,448) | — | 0.2% (5/2,424) |
Hair loss is covered in depth on GLP-1 hair loss; both labels link it to the weight loss itself. The fracture line is the label's own subgroup statement for women; it also reports more fractures in people aged 75 and over (2.4% against 0.6%).
Nausea, vomiting and other stomach effects are not published by sex in the current Zepbound or Wegovy labels. An analysis of 37,827 US adverse-event reports for tirzepatide found different reporting patterns — gastrointestinal terms more prominent among men's reports, administration-site and general terms among women's (Front Pharmacol 2024) — but a reporting database measures who files reports, not how often an effect happens. The class-wide side-effect record is on GLP-1 side effects.
Who is using them
A study of US commercial insurance claims (MarketScan, 2019–2024) found men and women used GLP-1 medicines at similar rates until Wegovy's weight approval in June 2021, after which women's use rose faster. By January 2024, adult women used them at 2.68 times the rate of men (163 against 61 users per 10,000), and for Wegovy specifically 4.03 times (Diabetes Obes Metab 2026).
What is not established
- Why women lose more on average. Pharmacokinetics do not explain it; nothing else has been tested directly.
- Whether side-effect rates beyond hair loss differ by sex. The labels do not say.
- Whether men should expect less. Averages overlap heavily; in every trial many men lost more than many women.
- Tirzepatide in the meta-analysis. The randomised sex-split evidence for tirzepatide is post-hoc or observational.
This page reports what the labels and studies found; it does not suggest a drug or a dose for anyone. Individual decisions belong with the prescriber. The trial results in full are on GLP-1 before and after; the drugs compared on best GLP-1 for weight loss.
Sources
- ZEPBOUND prescribing information, Eli Lilly, effective 2026-08-28 (DailyMed setid 487cd7e7-434c-4925-99fa-aa80b1cc776b): sections 6.1 (hair loss), 12.3 (specific populations), 14.
- WEGOVY prescribing information, Novo Nordisk, effective 2026-06-18 (DailyMed setid ee06186f-2aa3-4990-a760-757579d8f77b): sections 6.1 (hair loss, fractures), 12.3, 14.1–14.2.
- Sex differences in the efficacy of GLP-1 receptor agonists for weight reduction: a systematic review and meta-analysis. J Diabetes 2025 (PMID 40040445).
- Sex, not age, predicts weight loss outcomes with tirzepatide: a retrospective analysis. Obesity 2026 (PMID 42290037).
- Body weight reduction in women treated with tirzepatide by reproductive stage: post hoc analysis from SURMOUNT. Obesity 2025 (PMID 40074721).
- Sex-specific changes in GLP-1RA trends (2019–2024). Diabetes Obes Metab 2026 (PMID 41669827).
- Analysis of tirzepatide in FAERS: overall and sex-specific subgroups. Front Pharmacol 2024 (PMID 39568578).
- ClinicalTrials.gov posted baseline characteristics, read 28 September 2026: NCT05564117, NCT01272219, NCT03548935, NCT04184622, NCT05822830, NCT05869903, NCT05412004, NCT03574597.