Mounjaro side effects in women: what is common and what is urgent

SASian Anderson, Writer and editor, MyGLP. Sources checked 5 November 2026.

The most common side effects of Mounjaro in women are nausea, diarrhoea, vomiting, constipation and stomach pain, each affecting more than 1 in 10 people according to the patient leaflet. Most are mild to moderate and happen while the dose is being stepped up. Hair loss, injection site redness and gallstones are listed as common, up to 1 in 10.

The leaflet lists side effects for everyone, with no split by sex. Below are the frequency bands, the trial figures behind them, the signs to act on fast, and what is known about women in particular.

Side effects by how often they happen

You can read the full list in the Mounjaro patient leaflet. The NHS tirzepatide page gives the same common side effects and advice on coping with each.

Stomach side effects in the SURMOUNT-1 trial

In SURMOUNT-1, the 72-week trial of 2,539 adults where 67.5% were women, stomach side effects were the most common by far. The authors describe them as mostly mild to moderate and short-lived, and most happened during the 20 weeks when the dose was going up.

Read the placebo column with care. Nearly 1 in 10 people on a dummy injection reported nausea. Some of what you feel in the first weeks comes from eating less and eating differently, and our nausea-friendly meals guide has food that stays down. For constipation, see fibre and constipation.

Do women get more side effects than men?

There is no good answer yet, and the gap is worth naming. SURMOUNT-1 recruited more than 1,700 women, yet the published paper gives no side effect figures split by sex. Women made up most of the trial and the results still treat everyone as one group.

The only published look at sex comes from reports sent to the US drug regulator. A 2024 study in Frontiers in Pharmacology found 68.8% of the 37,827 tirzepatide reports came from women. Stomach symptoms stood out more strongly in the reports from men, and injection site rash and hives stood out in the reports from women. The authors warn that reports of this kind cannot measure risk, since nobody knows how many people took the medicine, and women may report more often. So the honest position is that nobody has shown women get more stomach side effects on Mounjaro. If your side effects are stopping you living normally, you have every right to be taken seriously.

Dehydration

Vomiting and diarrhoea drain fluid. The leaflet warns that fluid loss can reduce kidney function, and says to drink plenty of fluids when you start. The MHRA adds that severe dehydration can need a hospital visit. Our hydration guide has practical targets.

Hair loss and injection site reactions

Hair loss is a common side effect for weight management. The usual cause is fast weight loss, and the hair grows back. Our hair loss guide covers the timing and the blood tests worth asking for. Itching or redness where you inject is also common.

Gallbladder problems

Gallstones and gallbladder inflammation (cholecystitis) are listed as common, mainly in people using Mounjaro for weight loss. In SURMOUNT-1, gallbladder disease was reported by 0.8% to 1.7% of people on tirzepatide and 0.8% on placebo. The NHS lists severe tummy pain as the warning sign of gallbladder trouble and says to call 111 if you think you have a serious side effect.

Pancreatitis

Acute pancreatitis is an uncommon side effect, up to 1 in 100 people. In January 2026 the MHRA strengthened its warning. Between 2007 and October 2025 it received 1,296 Yellow Card reports of pancreatitis linked to GLP-1 and GLP-1/GIP medicines, 19 of them fatal, against around 25.4 million packs dispensed over five years.

The sign to know is severe stomach pain that does not go away. The pain may spread to your back and may come with nausea and vomiting. Early symptoms can look like ordinary side effects, so trust your sense that something is wrong. If pancreatitis is confirmed, the medicine is not restarted. Tell any doctor you see that you take Mounjaro, since a private prescription may not show in your GP record.

The pill and dose rises

Mounjaro slows your stomach, which may reduce how much of the pill you absorb. The MHRA says to use a barrier method such as condoms and not rely on the pill alone, above all for 4 weeks after starting and after each dose increase. Our contraception guide sets out every method.

Before each dose rise

1. Look back at the last 4 weeks. Note which side effects you had, on which days after the injection, and how bad they were.
2. Tell your prescriber about anything that stopped you eating, working or sleeping.
3. Ask whether to move up now or stay on your current dose for longer.
4. If you take the pill, plan a barrier method for the 4 weeks after the rise.
5. Keep fluids up in the days after the new dose.

Periods

Period changes are not listed in the leaflet, but many women notice a shift as their weight falls. Our periods guide explains why and when to see your GP.

Side effects tend to peak after a dose rise. Your prescriber can hold you at a dose for longer if you are struggling, so do not change your dose on your own. For the wider picture of what Mounjaro does, start with Mounjaro for women. Prices at every dose are on our Mounjaro price page.

Sources

1. Mounjaro KwikPen patient information leaflet (Eli Lilly, via the electronic medicines compendium)
2. Tirzepatide (NHS)
3. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1) (Jastreboff et al, New England Journal of Medicine, 2022)
4. Analysis of tirzepatide in the US FDA adverse event reporting system, including sex-specific subgroups (Ou et al, Frontiers in Pharmacology, 2024)
5. GLP-1 receptor agonists and dual GLP-1/GIP receptor agonists: strengthened warnings on acute pancreatitis (MHRA Drug Safety Update, January 2026)
6. GLP-1 medicines for weight loss and diabetes: what you need to know (MHRA, GOV.UK)
7. Women on skinny jabs must use effective contraception, MHRA urges (MHRA, GOV.UK)