Most side effects are the same for women and menThe label's side-effect table is not split by sex; it comes from trials in which 63% of participants were women (37% were men).[1] Women-specific findings are below. The full table is on Zepbound side effects.
Zepbound side effects hair loss: why women see it more
Hair loss was reported in 7.1% of women and 0.5% of men taking Zepbound in the pooled weight trials, against 1.3% of women and 0% of men on placebo.[1]
- 7.1%women on Zepbound with hair loss
- 0.5%men on Zepbound with hair loss
- 1.3%women on placebo
The label says these hair loss reports “were associated with weight reduction,” and no Zepbound-treated patient stopped treatment because of hair loss.[1] By dose, hair loss overall was 5% at 5 mg, 4% at 10 mg and 5% at 15 mg, versus 1% on placebo.[1]
Zepbound and birth control pills
Zepbound can make birth control pills less reliable, so the label advises a switch to a non-oral method, or adding a barrier method, for 4 weeks after starting and for 4 weeks after each dose increase.[1] The reason is slowed stomach emptying, which “is largest after the first dose and diminishes over time.” After a single 5 mg dose, peak levels of the pill hormone ethinyl estradiol fell by 59% and total exposure by 20%.[1]
| Event | Week | Backup needed through week |
|---|---|---|
| Start at 2.5 mg | 1 | 4 |
| Increase to 5 mg | 5 | 8 |
| Increase to 7.5 mg | 9 | 12 |
| Increase to 10 mg | 13 | 16 |
| Increase to 12.5 mg | 17 | 20 |
| Increase to 15 mg | 21 | 24 |
Arithmetic: if every step is taken at the earliest point, the 4-week windows join up, and backup contraception is needed continuously from week 1 to week 24. Staying on a dose longer ends the window sooner. Mounjaro carries the same advice.[2]
Zepbound and pregnancy
The label says Zepbound “may cause fetal harm” and should be stopped when a pregnancy is recognized.[1] It explains that weight loss “offers no benefit to a pregnant patient,” and that data in pregnant women are insufficient to judge the risk of birth defects or miscarriage. In animal studies, fetal growth reductions and abnormalities occurred at clinically relevant exposures.[1] Lilly runs a pregnancy exposure registry for people who become pregnant while taking it.[1]
Breastfeeding
In a study of 11 breastfeeding women given a single 5 mg dose, tirzepatide was undetectable in 164 of 171 breast-milk samples, and the total amount found was less than 0.02% of the dose.[1] There are no data on effects on the breastfed infant or on milk production, so the label asks that the benefits of breastfeeding be weighed against the mother's need for Zepbound.[1]
The common side effects, for everyone
Nausea (25–29%), diarrhea (19–23%), vomiting (8–13%) and constipation (11–17%) were the most common side effects across the 5, 10 and 15 mg doses, and most came while the dose was being increased.[1][3] How long they last is covered on how long do Zepbound side effects last, and dose steps on the tirzepatide dosage chart.
Related
- Zepbound side effectsThe full label tables by dose
- Tirzepatide half-lifeHow long it stays in the body
- Zepbound vs MounjaroSame drug, two labels
Frequently asked questions
Does Zepbound cause hair loss in women?
Hair loss was reported in 7.1% of women on Zepbound versus 1.3% on placebo, and the label links it to weight reduction. No one stopped Zepbound because of it in the trials.[1]
Does Zepbound affect birth control pills?
Yes, it can make them less effective. The label advises a non-oral or added barrier method for 4 weeks after starting and after each dose increase.[1]
Can you take Zepbound while pregnant?
No. The label says it may cause fetal harm and should be stopped when pregnancy is recognized.[1]
Can you take Zepbound while breastfeeding?
The label has limited data: very little tirzepatide reached breast milk in a small study, and effects on infants are unknown. It is a decision to make with a prescriber.[1]