Mounjaro vs Wegovy for Women: Which GLP-1 is Right for You?

If you've spent any time researching GLP-1 medications, you'll have noticed that Mounjaro (tirzepatide) produces more weight loss on average than Wegovy (semaglutide). The numbers in the trials are not subtle. So why isn't Mounjaro simply the obvious choice for everyone?

Because efficacy data is only part of the picture. NHS availability, cost, safety profile, and women-specific considerations, particularly around PCOS and perimenopause, all feed into a decision that should be tailored rather than defaulted.

This article compares the two head to head with women's health front and centre.

The Mechanism Difference Matters

Wegovy is a GLP-1 receptor agonist. It works by mimicking the action of the naturally occurring hormone GLP-1, which is released from the gut in response to food. This slows gastric emptying, stimulates insulin secretion, suppresses glucagon, and, crucially for weight management, acts on the hypothalamus to reduce appetite and food intake.

Mounjaro is a dual GIP/GLP-1 receptor agonist. It does everything semaglutide does through the GLP-1 pathway, and additionally activates GIP (glucose-dependent insulinotropic polypeptide) receptors. GIP is another gut hormone with roles in insulin secretion and, more importantly for body weight, fat metabolism and energy expenditure. The dual mechanism appears to produce synergistic effects on weight loss that go beyond what either pathway alone achieves.

This mechanistic difference is why the weight loss numbers differ so substantially in clinical trials.

Head-to-Head Efficacy: The Trial Data

The relevant trials are SURMOUNT-1 for Mounjaro and STEP 1 for Wegovy. They used different populations and designs, so direct comparison has limitations, but the numbers are instructive.

A direct head-to-head trial (SURMOUNT-5) confirmed what the separate trial data suggested: tirzepatide produced approximately 20% weight loss versus 14% for semaglutide over 72 weeks in the same trial population.

NHS Availability: A Critical Practical Difference

This is where the comparison shifts considerably.

Wegovy (semaglutide 2.4 mg) received NICE approval (TA875) for NHS use in obesity in 2023. It is available through specialist NHS weight management services, subject to BMI criteria. The waiting lists are long (12 to 24 months in most areas), but the NHS pathway exists. See the full guide to NHS Wegovy eligibility in 2026 for current criteria.

Mounjaro (tirzepatide) received NICE approval for obesity treatment (TA1026) in 2025, but NHS rollout for obesity is still in its early stages as of mid-2026. It is available via NHS for type 2 diabetes management, but the obesity pathway through specialist weight management services is only beginning to come online in some areas.

If your goal is NHS-funded treatment for obesity, Wegovy remains the more reliably available option in most parts of England.

Full Comparison

Women-Specific Considerations: PCOS

PCOS is the most common hormonal disorder in women of reproductive age in the UK, affecting around 1 in 10. Insulin resistance is central to its pathology in the majority of cases. GLP-1 medications improve insulin sensitivity both directly and via weight loss, which is why they have become a significant treatment option.

The evidence base for semaglutide in PCOS is stronger and more established than for tirzepatide. Multiple trials have now examined semaglutide specifically in women with PCOS, with consistent findings around androgen reduction, menstrual cycle normalisation, and metabolic improvement.

For tirzepatide, the PCOS-specific research is less mature. Its superior weight loss and the additional GIP mechanism (which may have independent effects on adipose tissue and ovarian function) make it an attractive theoretical candidate. But as of 2026, women with PCOS seeking evidence-based prescribing will find more clinical support for semaglutide.

For a comprehensive guide to GLP-1 medications in PCOS, see GLP-1 and PCOS: what the research shows.

Women-Specific Considerations: Perimenopause and Menopause

The hormonal changes of perimenopause, particularly the decline in oestrogen, cause significant shifts in body composition. Visceral fat accumulates, metabolic rate decreases, and insulin sensitivity often worsens. This is why the years around menopause are associated with weight gain that feels qualitatively different from earlier life.

Neither Mounjaro nor Wegovy has been specifically studied in peri or postmenopausal women as a primary trial population. However, subgroup analyses and real-world data suggest both medications work in this demographic, with the same efficacy patterns seen in the broader population.

The more relevant consideration for perimenopausal women may be the interaction with HRT. Both GLP-1 medications and HRT can be used simultaneously, and evidence suggests they address different aspects of the menopausal weight gain problem. HRT improves the hormonal environment; GLP-1 medications address appetite and energy regulation. The combination appears complementary. This is explored in detail in GLP-1 and menopause: can they help with midlife weight gain.

Muscle Loss Risk

Both medications carry a risk of lean mass loss alongside fat loss. This is a concern across all GLP-1 medications, particularly in women over 40 where muscle preservation is important for long-term metabolic health, bone density, and physical function.

Preliminary evidence suggests tirzepatide may have a slightly more favourable lean mass to fat mass loss ratio than semaglutide, possibly due to the GIP mechanism. This is not yet confirmed in dedicated trials in women. In practice, the most effective mitigation for both medications is adequate protein intake and resistance training. See the full guide on muscle loss prevention on GLP-1 for women for specifics.

Side Effect Profiles Compared

The GI side effects of both medications are similar in nature: nausea, vomiting, diarrhoea, and constipation, particularly in the early weeks of dose escalation. Both typically improve significantly after the first 4 to 8 weeks.

In comparative trial data, the two profiles are broadly similar in frequency at equivalent efficacy doses. Some analyses have suggested slightly higher rates of nausea with tirzepatide at the higher doses (10 mg and 15 mg), though this is not a consistent finding across all studies.

The key practical difference: because tirzepatide is more potent and produces more weight loss, it may also produce more pronounced GI effects during dose escalation. Careful dose titration is important with both medications.

For the full side effect picture, see the GLP-1 side effects guide.

Price: What You'll Actually Pay Privately

NHS pricing aside, here is what private treatment typically costs in the UK as of mid-2026:

Wegovy (semaglutide):

• Starting dose (0.25 mg): £120-160/month
• Maintenance dose (2.4 mg): £180-260/month
• Varies significantly by clinic and whether consultation fees are included

Mounjaro (tirzepatide):

• Starting dose (2.5 mg): £130-180/month
• Maintenance dose (10-15 mg): £220-300/month
• Again varies by clinic

These are rough ranges. Prices have fallen from 2023 peaks as supply improved, but Mounjaro remains more expensive on average.

Choosing a Private Clinic

Whichever medication you choose, the clinic matters as much as the medication. A good clinic will take a full medical history, run baseline bloods, check contraindications, and provide genuine follow-up. Red flags include clinics that issue prescriptions without assessment or that cannot answer questions about side effects and monitoring.

For a full breakdown of how to evaluate private GLP-1 clinics in the UK, see best GLP-1 clinic UK 2026.

The Honest Recommendation

If you are accessing medication privately with no significant budget constraint: Mounjaro has better efficacy data and may suit women who have struggled to lose weight on other interventions. The gap between 15% and 22% body weight loss is substantial.

If you are on the NHS or near the eligibility threshold: Wegovy is the realistic option and 15% body weight loss is a clinically meaningful, life-changing result.

If you have PCOS as a primary concern: semaglutide (Wegovy, or the lower-dose Ozempic) has more direct evidence in this population. Tirzepatide may well be as good or better, but the evidence base is not yet there.

If perimenopause weight gain is your main concern: both medications are relevant. The HRT interaction is worth discussing with a prescriber. See the menopause article for a more detailed breakdown.