Who was in the trials, and what is split by sex
Weight-management trials enrolled mostly women, while the type 2 diabetes trials behind Ozempic® and Mounjaro® enrolled slightly more men [1][3][6]. The table shows the share of women in each label’s main safety pool and the results the label reports separately for women.
- The Wegovy®, Ozempic®, Mounjaro® and Foundayo™ labels say sex had no clinically meaningful effect on drug levels [1][3][5][6].
- Ozempic® and Mounjaro® effectiveness did not differ by gender, and Wegovy®’s heart benefit was not affected by sex [1][3][6].
| Label and pool | Women | Reported by sex |
|---|---|---|
| Wegovy® 2.4 mg injection, weight trials [1] | 71% | Hair loss 4% of women vs 0.9% of men (placebo 2% vs 0%); fractures in the heart outcomes trial |
| Wegovy® 7.2 mg injection [1] | 70% | Hair loss 8.4% of women vs 0.2% of men |
| Wegovy® tablets [1] | 76% | Not split by sex |
| Zepbound®, two weight trials [2] | 63% | Hair loss 7.1% vs 0.5% (placebo 1.3% vs 0%) |
| Foundayo™, two trials [5] | 59% | Hair loss 7% vs 0.9% (placebo 3% vs 0.7%) |
| Saxenda®, adult trials [4] | 71% | Breast cancer 0.7% vs 0.2% on placebo in women |
| Ozempic®, placebo-controlled pool [6] | 45% | Not split by sex |
| Mounjaro®, placebo-controlled pool [3] | 46% | Not split by sex |
Side effects the labels report for women
- Hair loss: more frequent in women in every label that splits it, and linked by the labels to weight reduction [1][2][5]. The hair loss article covers rates, timing and other causes in detail.
- Fractures: in the Wegovy® heart outcomes trial, hip and pelvis fractures were reported in 1% of women on semaglutide (24 of 2,448) against 0.2% on placebo (5 of 2,424); the same pattern appeared in people aged 75 and over [1]. The label does not give a cause.
- Breast cancer: in Saxenda® adult trials, confirmed breast cancer was reported in 0.7% of women on liraglutide (17 of 2,379) against 0.2% on placebo (3 of 1,300), mostly hormone-receptor positive. The label says there were too few cases to tell whether they were related to the medicine, and too little data on existing breast tumours [4].
- Animal fertility findings: in rats, semaglutide lengthened the estrous cycle and tirzepatide prolonged one phase of it, which the labels put down to reduced food intake and body weight [1][2]. Orforglipron showed no effect on rat fertility [5]. The labels report no effect on human fertility.
What studies report on stomach side effects
A post hoc analysis of SUSTAIN 7, which compared semaglutide with dulaglutide in about 1,200 adults with type 2 diabetes, found that stomach side effects were reported by more women than men with both medicines; with semaglutide they also became less frequent as body mass index rose [7]. A patient-level analysis of trials comparing weekly exenatide with twice-daily exenatide or with liraglutide found the same within every treatment group: more women than men reported stomach side effects, mostly mild and early [8].
A narrative review of sex differences with GLP-1 medicines concludes that differences have been seen in blood sugar response, weight loss and side effect frequency, and that the reasons are still being studied [9]. These analyses were not designed to test sex differences, and they cannot separate sex from body size, dose per kilogram or reporting habits. None looked at tirzepatide or the newest weight-management doses.
Why differences may appear
- Supported by the labels: hair loss is tied to weight reduction, and the female share of trial populations means most label data already reflect women [1][2].
- Proposed but not measured: the Saxenda® label reports that women clear liraglutide about 24% more slowly once body weight is accounted for, and the Ozempic® label says semaglutide exposure falls as body weight rises [4][6]. Higher exposure in lighter people could play a part in the stomach findings above, but neither label links these facts to side effects [4][6][7].
- General: osteoporosis is more common in older women, with the drop in estrogen at menopause and low body weight among the risk factors MedlinePlus lists [12]. That background may matter when reading the fracture finding, though the label does not explain it [1][12].
Birth control, pregnancy and breastfeeding, in brief
The Mounjaro® and Zepbound® labels say tirzepatide may make birth control pills less effective, with set windows after starting and after each dose increase; the Foundayo™ label uses longer windows and also asks women who could become pregnant to use effective contraception [2][3][5]. The semaglutide and liraglutide labels do not carry this instruction. The article on oral contraceptives and GLP-1 medicines goes through each label and section 8.3 in turn.
The weight-management labels say weight loss offers no benefit in pregnancy and treatment should stop once a pregnancy is recognised, and the semaglutide labels ask for a gap of at least two months before a planned pregnancy [1][2][6]. The pregnancy article covers sections 8.1 to 8.3 for every label, and the postpartum topic page covers breastfeeding.
What else could it be
Nausea in a woman of childbearing age has a cause that matters more than usual on these medicines: MedlinePlus lists morning sickness in pregnancy among the common causes, and asks whether you could be pregnant when assessing nausea [10]. Because the tirzepatide and orforglipron labels warn that pill effectiveness can drop at certain times, mention any chance of pregnancy when you report new or unexpected nausea [2][5][10].
Hair shedding can follow childbirth, crash dieting, severe stress, thyroid disease or anemia, and some medicines including birth control pills, according to MedlinePlus [11]. Cycle changes, hot flashes and tiredness have many causes too; the periods and menopause topic pages look at those alongside GLP-1 treatment.
What to raise with your prescriber
A few dates make these conversations easier: when you started, each date the dose went up, your contraception method, cycle dates if you track them, and the date you first noticed hair shedding or any other change. If you have had breast cancer, mention it, since the Saxenda® label notes too little data on existing breast tumours [4]. If you are older or have had a fracture, bone health is worth raising given the Wegovy® finding [1][12].
Ozempic®, Wegovy® and Saxenda® are registered trademarks of Novo Nordisk A/S. Mounjaro® and Zepbound® are registered trademarks and Foundayo™ is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Novo Nordisk or Eli Lilly and Company.
When to get help
| Sign | Who to contact | How fast | Source |
|---|---|---|---|
| A positive pregnancy test, or a possible pregnancy, while on a weight-management GLP-1 | Your prescriber, to discuss stopping | Today | Wegovy® and Zepbound® labels, section 8.1 [1][2] |
| New or unexpected nausea with a missed period while using birth control pills | Your prescriber or pharmacist | Today | Zepbound® label, section 8.3 [2]; MedlinePlus [10] |
| Hair loss that is rapid, patchy, or comes with acne, facial hair or an irregular cycle | Your clinician | At your next appointment | MedlinePlus Hair loss [11] |
| Planning a pregnancy in the coming months | Your prescriber | At your next appointment | Ozempic® and Wegovy® labels, section 8.3 [1][6] |
| A history of breast cancer or of fractures before or during treatment | Your prescriber | At your next appointment | Saxenda® and Wegovy® labels [1][4] |
