Tier 1: Proven in large outcome trials
Cardiovascular protection (semaglutide 2.4 mg. SELECT)
The landmark. In the SELECT trial (17,600 people with existing cardiovascular disease and overweight/obesity, but no diabetes), Wegovy cut major cardiovascular events (heart attack, stroke and cardiovascular death) by 20% over roughly three years versus placebo. Crucially, benefits appeared before major weight loss, suggesting direct effects on blood vessels and inflammation, not just kilograms. NICE responded with TA1152, recommending semaglutide for reducing cardiovascular risk in this exact group. Making Wegovy the first weight-management medicine recommended by NICE to prevent heart events.
Kidney protection (semaglutide. FLOW)
In people with type 2 diabetes and chronic kidney disease, semaglutide (diabetes doses) reduced the risk of major kidney outcomes. Kidney failure, substantial decline in kidney function, and kidney- or cardiovascular-related death. By 24% in the FLOW trial. The trial was stopped early because the benefit was so clear.
Obstructive sleep apnoea (tirzepatide. SURMOUNT-OSA)
In adults with obesity and moderate-to-severe sleep apnoea, tirzepatide reduced the number of apnoea events per hour by roughly half to two-thirds versus placebo, and many participants no longer met the threshold for moderate disease. Sleep apnoea is a driver of blood pressure, arrhythmia and daytime exhaustion. This is a quality-of-life result, not just a statistic.
Heart failure with preserved ejection fraction (HFpEF)
Both molecules now have positive HFpEF trials. STEP-HFpEF (semaglutide) and SUMMIT (tirzepatide) showed big improvements in symptoms and physical function. SUMMIT also reduced the combined risk of cardiovascular death and worsening heart-failure events. For a condition with few effective treatments, cardiologists have taken notice.
Tier 2: Strong, consistent evidence
Prediabetes reversal
Across the SURMOUNT and STEP programmes, the overwhelming majority of participants with prediabetes reverted to normal blood sugar on treatment. Over 95% in some tirzepatide cohorts. For people on the trajectory to type 2 diabetes, that is the closest thing medicine has to a U-turn.
Blood pressure, lipids and inflammation
Consistent, meaningful improvements: systolic blood pressure down typically 5 to 10 mmHg, triglycerides down, HDL up, and the inflammation marker hsCRP down by around 40% in SELECT. Each individually modest; together, a materially better cardiometabolic profile.
MASH (fatty liver disease)
In the ESSENCE trial (semaglutide) and SYNERGY-NASH (tirzepatide), a majority of participants with MASH achieved resolution of the inflammatory liver disease without worsening fibrosis, and fibrosis itself improved in a substantial minority. No licensed MASH-specific indication yet in the UK, but the evidence is among the strongest in hepatology right now.
Tier 3: Promising. Not yet proven
- Knee osteoarthritis. STEP 9 (semaglutide) significantly reduced pain and improved function in people with obesity and knee OA. Plausibly mechanical (less load) plus anti-inflammatory.
- PCOS. Smaller studies show weight loss, improved cycles and reduced androgens, but no large outcome trials yet, and these medicines are avoided in pregnancy.
- Addiction pathways. Early observational signals around reduced alcohol and substance use are genuinely interesting, and nowhere near proven. Treat headlines accordingly.
Keeping perspective
1. Most benefits shrink when treatment stops. The SELECT-era evidence supports these as long-term therapies, and stopping usually means losing both weight and metabolic gains (see maintenance after Mounjaro). 2. "Proven" applies to specific studied populations. SELECT enrolled people with existing heart disease, FLOW people with diabetes and kidney disease. 3. Serious risks exist alongside benefits. Pancreatitis warnings, gallbladder disease, and the MHRA's NAION signal for semaglutide are covered in our side effects guide. Benefits and risks are always weighed together with a prescriber.
And a practical note: these benefits only materialise with genuine medicine, taken consistently. If you are comparing providers, Monj.co.uk (Mounjaro) and iGovy.co.uk (Wegovy) manually verify pharmacies so the medicine in your pen is the medicine in these trials.
Monj.co.uk
An independent UK service that manually checks every pharmacy it lists. That means GPhC registration, proper prescribing and reliable cold-chain delivery, all confirmed before a pharmacy is recommended for Mounjaro.
Check verified providers → Manually verified For Wegovy injectionsiGovy.co.uk
An independent UK service that manually checks Wegovy providers. GPhC registration, genuine Novo Nordisk stock and proper refrigerated delivery are all confirmed before a provider is listed.
Check verified providers →Frequently asked questions
Do Mounjaro and Wegovy protect the heart? +
Wegovy has the strongest proof: the SELECT trial showed a 20% reduction in major cardiovascular events in people with existing heart disease and obesity, leading to NICE TA1152. Tirzepatide's dedicated cardiovascular outcomes trial (SURMOUNT-MMO) is still ongoing.
Can GLP-1 medicines help sleep apnoea? +
Yes. In SURMOUNT-OSA, tirzepatide roughly halved to two-thirds the number of apnoea events per hour in people with obesity and moderate-to-severe obstructive sleep apnoea. It does not replace CPAP where that is prescribed.
Do these medicines reverse prediabetes? +
In the major trials, the large majority of participants with prediabetes returned to normal blood glucose on treatment. Over 95% in some tirzepatide cohorts. Reversal persists mainly while treatment (and the weight loss it produces) continues.
Are the benefits just from losing weight? +
Partly, but not entirely. In SELECT, cardiovascular benefit appeared before substantial weight loss, and inflammation markers fell sharply, suggesting direct effects on blood vessels and inflammation beyond kilograms lost.
Which is better for overall health. Mounjaro or Wegovy? +
Wegovy currently has the broader completed outcomes evidence (SELECT, FLOW, STEP-HFpEF). Mounjaro produces greater average weight loss and has positive sleep apnoea and HFpEF data, with its big cardiovascular outcomes trial still running. Our Mounjaro vs Wegovy comparison goes deeper.
References & official sources
Show all 7 cited sources, with study authors +
- Lincoff AM et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). NEJM 2023: www.nejm.org/doi/full/10.1056/NEJMoa2307563
- Perkovic V et al. Effects of Semaglutide on Chronic Kidney Disease in Patients with Type 2 Diabetes (FLOW). NEJM 2024: www.nejm.org/doi/full/10.1056/NEJMoa2403347
- Malhotra A et al. Tirzepatide for the Treatment of Obstructive Sleep Apnea and Obesity (SURMOUNT-OSA). NEJM 2024: www.nejm.org/doi/full/10.1056/NEJMoa2404881
- Packer M et al. Tirzepatide for Heart Failure with Preserved Ejection Fraction and Obesity (SUMMIT). NEJM 2025: www.nejm.org/doi/full/10.1056/NEJMoa2410027
- NICE TA1152. Semaglutide for reducing the risk of major adverse cardiovascular events: www.nice.org.uk/guidance/ta1152
- NICE TA1026. Tirzepatide for managing overweight and obesity: www.nice.org.uk/guidance/ta1026
- NICE TA875. Semaglutide for managing overweight and obesity: www.nice.org.uk/guidance/ta875