Tirzepatide for Women: What the SURMOUNT Trials Report by Sex
Women lost more weight than men on tirzepatide in Lilly's pooled analysis, and also reported more nausea, vomiting and hair loss. Here is what the numbers say, where they come from, and how much weight to put on them.
Women in the SURMOUNT trials lost more weight on tirzepatide (Zepbound) than men did, on average, and they also reported more gastrointestinal side effects and much more hair loss. The sex data come from post hoc subgroup analyses, not from trials designed to compare women and men, so the direction of the difference is more reliable than the exact size. The practical takeaway: women tend to respond well to tirzepatide and should expect a rougher first few months with GI symptoms.
The SURMOUNT program in one paragraph
SURMOUNT is Lilly's set of phase 3 trials of tirzepatide for weight management. The first, SURMOUNT-1 (Jastreboff et al., NEJM 2022), enrolled 2,539 adults with obesity or overweight without diabetes and ran for 72 weeks. Mean weight change was roughly 15% to 21% across the three tirzepatide doses, versus 3.1% with placebo, and between 85% and 91% of people on tirzepatide lost at least 5% of their body weight, compared with 35% on placebo. Later trials tested people with type 2 diabetes (SURMOUNT-2), people who first went through an intensive lifestyle program (SURMOUNT-3), and what happens when people stop the drug after a run-in period (SURMOUNT-4).
None of these trials was built to compare women with men. Sex was one of many characteristics recorded, and the analyses below slice the data afterwards.
What the sex-subgroup analyses found
Weight loss: women lost more
Lilly researchers presented a pooled analysis of four SURMOUNT trials at the European Association for the Study of Diabetes meeting in September 2024. As reported by HealthDay, it included nearly 3,000 women and 1,700 men and found:
- All tirzepatide doses reduced weight in both women and men.
- Women lost up to about 24.6% of initial body weight, versus about 18.1% in men.
- Compared with placebo, women lost roughly 12% to 28% more weight across trials and doses; men lost roughly 9% to 19% more.
A separate Lilly subgroup analysis by sex across SURMOUNT-1 to -4 (Chao et al., Lilly medical poster, 2024) labels itself post hoc and exploratory. It compared tirzepatide with placebo within each sex; it did not report a formal test of whether the treatment effect differed between women and men.
Side effects: women reported more nausea, vomiting and hair loss
- Nausea and vomiting: the Chao poster states these were consistently reported more often in females than males across studies. It does not give the percentages in its public summary.
- Hair loss: the Zepbound prescribing information reports hair loss in 7.1% of women versus 0.5% of men taking tirzepatide in the weight-reduction trials. Our guide to GLP-1 hair shedding covers why this happens and what helps.
- Overall safety: the EASD presentation described the overall safety profile as similar between sexes.
Drug levels: sex doesn't change them meaningfully
The label states that sex has no clinically relevant effect on tirzepatide's pharmacokinetics. In other words, women don't simply end up with more drug in their blood at the same dose, at least not enough to matter by the label's standard. Why women lose more weight is not established. The EASD presenters said more research is needed on the mechanism.
Why might women lose more? Hypotheses, not answers
Researchers have floated several explanations, none confirmed for tirzepatide:
- Body composition. Women generally carry a higher share of body weight as fat. If a drug mostly reduces fat mass, the percentage change on the scale can look different between sexes even when the underlying effect is similar.
- Body size and exposure. Women are, on average, smaller, and every participant on a given dose received the same fixed amount. The label says sex itself has no clinically relevant effect on drug levels, but body weight does affect exposure for many drugs.
- Hormones and appetite. Estrogen interacts with appetite and energy-balance signaling, and GLP-1 pathways are part of that system. Whether this changes the response to tirzepatide hasn't been tested directly.
- Side effects and eating. If women experience more nausea, they may eat less in the early months. That could add to weight loss, but it is a trade-off, not a benefit.
Any of these could contribute. None should be quoted as "the reason" yet.
What happens when treatment stops
SURMOUNT-4 put everyone on tirzepatide for an initial period, then randomly assigned people to keep taking it or switch to placebo. Those switched to placebo regained a substantial share of the weight they had lost, while those who continued kept losing or held steady. The Chao poster's sex analysis includes SURMOUNT-4, and the regain pattern is the part most women ask about: tirzepatide works while you take it, and stopping is a decision to plan with your prescriber rather than a finish line.
How much to trust these numbers
| Strength | Limitation |
|---|---|
| Large numbers of women: nearly 3,000 in the pooled analysis | Post hoc and exploratory; trials weren't designed to compare sexes |
| Consistent direction across four trials and all doses | Presented at a conference and funded by the manufacturer; peer-reviewed publication should be checked |
| Placebo-controlled comparisons within each sex | Women and men differ in body composition, which makes percent-weight comparisons harder to interpret |
| Label data on hair loss come from FDA-reviewed trial data | Side-effect reporting can differ by sex for reasons other than biology (who notices, who reports) |
A fair summary: women in these trials did at least as well as men, probably better, and had a more uncomfortable ride. That's useful for setting expectations. It isn't a reason to expect a specific number for yourself.
What this means if you're a woman considering tirzepatide
Expect GI side effects, and plan for them
In the label's pooled weight-reduction trials, nausea was reported by 25% to 29% of people on tirzepatide (by dose) versus 8% on placebo, constipation by 11% to 17% versus 5%, and vomiting by 8% to 13% versus 2%. If women report these more often, a plan for the first months matters: smaller meals, stopping at the first sign of fullness, fluids, and knowing which symptoms mean "call now."
Check your contraception
The Zepbound label says tirzepatide may reduce the effectiveness of birth control pills and advises a non-oral method or an added barrier method for 4 weeks after starting and after each dose increase. With weight loss, ovulation can also return in women whose cycles were irregular. See GLP-1s and your period for what to watch.
Protect muscle while you lose fat
Big weight loss means losing some lean mass along with fat. For women heading into or through menopause, when muscle and bone are already under pressure, protein intake and resistance training matter. Our guide to GLP-1 muscle loss in women goes through the evidence.
Dosing is your prescriber's call
Some women wonder whether a stronger response means they need a lower dose. That is a reasonable question to ask, and it is the prescriber's decision. Dosing for prescription peptides is set by the prescribing clinician. Our GLP-1 dosing overview for women explains how titration works in general terms.
Questions to bring to your appointment
- Given that women report more nausea and vomiting, what's our plan if I can't tolerate a dose increase?
- Do I need to change my birth control, and for how long?
- How will we track muscle, not just weight?
- If I'm planning a pregnancy in the next year or two, how does that change things?
- How does tirzepatide compare with semaglutide for someone like me? (See our semaglutide vs tirzepatide comparison.)
Prescription Option (Telehealth)
Brand-name tirzepatide is FDA-approved as Zepbound and Mounjaro. Some telehealth services prescribe compounded versions instead.
HealthRX offers prescription telehealth. A licensed clinician reviews your intake and decides whether a medication is appropriate. Compounded tirzepatide is not FDA-approved, and results vary.
The bottom line
The SURMOUNT data suggest women respond well to tirzepatide, with larger average weight loss than men, and that women carry more of the side-effect burden, especially nausea, vomiting and hair loss. Those findings come from analyses done after the fact, so they set expectations rather than predict your result. For more on tirzepatide itself, see our tirzepatide profile.
Sources
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022.
- Chao A, Taylor R, Mojdami D, et al. Body weight reduction associated with tirzepatide by sex: a subgroup analysis of the SURMOUNT clinical trials. Eli Lilly medical poster, 2024.
- HealthDay. Weight-Loss Drug Zepbound May Work Better in Women Than Men. September 12, 2024 (reporting the EASD 2024 presentation).
- Eli Lilly. Zepbound (tirzepatide) prescribing information.