The best weight loss injection for women: Mounjaro or Wegovy?

One trial has put Mounjaro and Wegovy side by side, and most of the people in it were women. Here is what it found, and what else should shape your choice.

By Sian Anderson. Published 5 November 2026. 7 minute read. Information, not medical advice.

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

Mounjaro (tirzepatide) leads to more weight loss than Wegovy (semaglutide). In SURMOUNT-5, the head-to-head trial, people on Mounjaro lost 20.2% of their body weight over 72 weeks, against 13.7% on Wegovy. Wegovy has the stronger heart evidence. The best one for you is the one you can take, keep taking and afford.

SURMOUNT-5: both medicines in the same trial

SURMOUNT-5, published in the New England Journal of Medicine in 2025, enrolled 751 adults with obesity and no type 2 diabetes. 64.7% were women. Each person took the highest dose they could tolerate, once a week, for 72 weeks. For Mounjaro that was 10mg or 15mg. For Wegovy it was 1.7mg or 2.4mg.

SURMOUNT-5, Aronne et al, New England Journal of Medicine, 2025. Highest tolerated dose of each medicine.
Result at 72 weeks	Mounjaro	Wegovy
Average weight lost	20.2%	13.7%
Average weight lost in kg	22.8 kg	15.0 kg
Average drop in waist size	18.4 cm	13.0 cm
Lost at least 10% of body weight	81.6%	60.5%
Lost at least 15%	64.6%	40.1%
Lost at least 20%	48.4%	27.3%
Lost at least 25%	31.6%	16.1%

The paper also reports weight loss about 6% greater in women than in men on both medicines. Our guide on whether women lose more weight on Mounjaro looks at that finding and the research behind it.

What the earlier placebo trials found

Before SURMOUNT-5, each medicine was tested against a dummy injection. STEP 1 tested Wegovy in 1,961 adults, 74.1% of them women. SURMOUNT-1 tested Mounjaro in 2,539 adults at three doses. The two trials used different people over different lengths of time, so set side by side they give a rough guide only. SURMOUNT-5 is the fair comparison.

Wilding et al, NEJM 2021. Jastreboff et al, NEJM 2022. Doses are the trial doses, given as facts and not as advice.
Trial	Medicine	Length	Average loss on medicine	Average loss on placebo
STEP 1 (2021)	Wegovy 2.4mg	68 weeks	14.9%	2.4%
SURMOUNT-1 (2022)	Mounjaro 5mg	72 weeks	15.0%	3.1%
SURMOUNT-1 (2022)	Mounjaro 10mg	72 weeks	19.5%	3.1%
SURMOUNT-1 (2022)	Mounjaro 15mg	72 weeks	20.9%	3.1%

For the early weeks on Mounjaro, including the 2.5mg starting dose, see our guide to Mounjaro weight loss in the first month.

Side effects: closer than the weight figures

Stomach side effects were common on both medicines in SURMOUNT-5, and the rates were close. Vomiting was the clear difference. Fewer people stopped Mounjaro because of side effects.

SURMOUNT-5, Aronne et al, New England Journal of Medicine, 2025.
Side effect in SURMOUNT-5	Mounjaro	Wegovy
Nausea	43.6%	44.4%
Constipation	27.0%	28.5%
Diarrhoea	23.5%	23.4%
Vomiting	15.0%	21.3%
Stopped treatment because of side effects	6.1%	8.0%

The patient leaflets list the same group as very common, meaning more than 1 in 10 people. The Mounjaro leaflet names nausea, diarrhoea, vomiting, stomach pain, constipation, tiredness and lower appetite. The Wegovy leaflet adds headache. Hair loss and gallstones appear in the Mounjaro leaflet as common, up to 1 in 10. Our guide to Mounjaro side effects in women goes through each, and our nausea-friendly meals help with the first weeks.

How often you inject, and the tablet options

Both pens are once a week, on the same day each week if you can.

If needles put you off, two daily tablets are licensed in the UK: the Wegovy pill (semaglutide) and Foundayo (orforglipron). The Wegovy tablet leaflet sets firm rules. You take the tablet on an empty stomach after at least 8 hours without food, swallow it with a sip of water of up to 120ml, and wait at least 30 minutes before eating, drinking or taking other tablets. Neither pill is available on the NHS at present, so both are private only. You can set all four medicines side by side on our compare page.

Heart evidence: where Wegovy leads

The SELECT trial gave semaglutide or placebo to 17,604 adults aged 45 or over with existing heart or circulation disease, a BMI of 27 or more and no diabetes. Heart attack, stroke or heart death happened to 6.5% of people on semaglutide and 8.0% on placebo, a 20% lower risk. SELECT tested people who already had heart disease, so the result does not apply to everyone. If heart disease is part of your history, that result may matter more to you than a few extra kilos. Our heart health after menopause guide covers SELECT and your own heart numbers.

Points women ask about first

The pill and Mounjaro. The NHS advises extra barrier contraception, such as condoms, for 4 weeks after starting and 4 weeks after each dose increase. Our contraception guide sets out your options.
Planning a pregnancy. The NHS says to stop Mounjaro at least 4 weeks before you start trying. The Wegovy leaflet says to stop at least two months before. See our fertility and pregnancy guide.
Breastfeeding. The Wegovy leaflet says not to use the medicine while breastfeeding. Talk to your GP or health visitor before starting either one after a birth.
PCOS and the menopause. For how each condition fits with the medicines, see our PCOS guide and perimenopause guide.

Which one you can get on the NHS

NICE has approved both injections for weight loss, with different rules. Wegovy comes through NICE TA875. Mounjaro comes through NICE TA1026, which NHS England is rolling out in phases.

NICE TA875 and NHS England interim commissioning guidance for NICE TA1026.
NHS rule	Wegovy (NICE TA875)	Mounjaro (NICE TA1026)
Headline criteria	BMI of 35 or more with at least 1 weight-related condition, or BMI 30 to 34.9 and meeting the criteria for specialist referral	BMI of 35 or more with at least 1 weight-related condition
Where you get it	A specialist weight management service	Specialist services and, in phases, GP surgeries
Who gets it first	Set by the criteria above	In GP care, year 1 covers a BMI of 40 or more with at least 4 qualifying conditions
Time limit or rollout	Up to 2 years	Full rollout over up to 12 years, about 220,000 people in the first 3 years

Both sets of rules use lower BMI thresholds, usually 2.5 lower, for people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family backgrounds. If you do not qualify yet, private prescriptions are the other way in. Current prices for every dose are on our Mounjaro price page.

How to weigh up your choice

Decide how much the size of the weight loss matters to you. SURMOUNT-5 favours Mounjaro.
Check your heart history. If you have heart disease, ask about the SELECT evidence for Wegovy.
Think about side effects you have had before. Vomiting was less common on Mounjaro in SURMOUNT-5.
Choose between a weekly injection and a daily tablet with fasting rules.
Check what you can afford each month, for as long as you plan to take the medicine. Compare all four on our compare page.

Call NHS 111 if you take either medicine and get severe pain in your stomach or back which does not go away, or severe tummy pain. The NHS tirzepatide page lists these as possible signs of pancreatitis or gallbladder problems.

Paying for your own medicine? The lowest first-order prices today, with delivery included: Mounjaro from £89.00, Wegovy from £44.00, Wegovy pill from £52.99, Foundayo from £49.00.

Compare every price Discount codes

Sources

Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5) (Aronne et al, New England Journal of Medicine, 2025 (author manuscript, Weill Cornell eCommons))
Once-weekly semaglutide in adults with overweight or obesity (STEP 1) (Wilding et al, New England Journal of Medicine, 2021 (open access copy, University of Leicester))
Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1) (Jastreboff et al, New England Journal of Medicine, 2022 (abstract, Weill Cornell))
Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT) (Lincoff et al, New England Journal of Medicine, 2023 (open access copy, UCL Discovery))
Mounjaro KwikPen patient information leaflet (Electronic Medicines Compendium)
Wegovy pen patient information leaflet (Electronic Medicines Compendium)
Wegovy tablets patient information leaflet (Electronic Medicines Compendium)
Semaglutide for managing overweight and obesity (TA875) (NICE)
Interim commissioning guidance: implementation of NICE TA1026 (tirzepatide) (NHS England)
Tirzepatide (NHS)

Sian Anderson

Sian writes the health and nutrition guides on MyGLP. Every clinical claim links to the NHS, NICE, a medical royal college, a regulator or a peer-reviewed paper, and the pages carry no medical advice.

Questions

Is Mounjaro better than Wegovy for women?

For weight loss, yes on average. In SURMOUNT-5, where 64.7% of people were women, Mounjaro led to 20.2% weight loss over 72 weeks against 13.7% on Wegovy. Wegovy has heart outcome evidence from SELECT in people with existing heart disease.

Which weight loss injection has the fewest side effects?

In SURMOUNT-5 the rates of nausea, constipation and diarrhoea were close on both. Vomiting affected 15.0% on Mounjaro and 21.3% on Wegovy, and 6.1% against 8.0% stopped because of side effects.

How often do you inject Mounjaro and Wegovy?

Both are injected once a week, on the same day each week if you can. The Wegovy pill and Foundayo are daily tablets instead, and neither is available on the NHS at present.

Can I get Mounjaro or Wegovy on the NHS?

Both are NICE approved with strict criteria. Wegovy is prescribed through specialist weight management services for up to 2 years. Mounjaro is being rolled out in phases, starting in GP care with people who have a BMI of 40 or more and at least 4 qualifying conditions.

Is there a weight loss pill instead of an injection?

Yes. The Wegovy pill and Foundayo are licensed daily tablets in the UK. The Wegovy pill must be taken on an empty stomach with a small sip of water. Both are private only at present.