SURMOUNT-OSA Tirzepatide Weight Loss Percentage Explained (October 2026)

01 · The core answer

What SURMOUNT-OSA showed about weight loss

SURMOUNT-OSA enrolled adults living with both obesity and obstructive sleep apnoea and compared tirzepatide with placebo.¹⁶ Weight loss was a key measure, alongside changes in the number of breathing interruptions per hour of sleep. Tirzepatide substantially reduced the severity of obstructive sleep apnoea in adults with obesity — on average, breathing interruptions fell by around half or more over a year.¹⁶

If you want a deeper look at the breathing measures, our guide to the apnoea-hypopnoea index reduction covers how that outcome is measured.

02 · Your decision

Is the SURMOUNT-OSA result relevant to you?

It is relevant if you have obesity and sleep apnoea and are weighing up treatment, but it does not replace a conversation with your sleep clinician. Mounjaro's UK licence covers weight management in adults and type 2 diabetes.¹ Whether it suits you depends on your health history, your current sleep-apnoea care and your goals.

Treatment is used alongside a reduced-calorie diet and increased physical activity, and individual results vary.¹ Tirzepatide is not a substitute for any breathing treatment you have been prescribed. Do not change or stop sleep-apnoea therapy without speaking to the clinician who manages it.

If you are ready to explore treatment for weight, you can start with our free consultation for the Mounjaro pen, reviewed by a GPhC-registered prescriber, or read our wider weight loss clinic overview first.

03 · SURMOUNT-1 averages

SURMOUNT-1 tirzepatide weight-loss averages

For exact tirzepatide weight-loss percentages, SURMOUNT-1 gives the averages over 72 weeks. In the SURMOUNT-1 trial of 2,539 adults, people taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.²

These are trial averages — individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight. Half of participants on 10mg and 57% on 15mg lost at least 20% of their body weight.²

SURMOUNT-1 did not select people for sleep apnoea, so it answers a different question from SURMOUNT-OSA. It is a different trial from SURMOUNT-OSA. More trial comparisons sit in our guide to tirzepatide weight loss percentages across trials, and the full SURMOUNT-1 results have their own page.

04 · SURMOUNT-2 and others

SURMOUNT-2 and other trials: do not mix them up

SURMOUNT-2 is not SURMOUNT-OSA, and its figures should never be quoted as if they were. Each trial in the SURMOUNT programme enrolled a different population and asked a different question.

A few rules keep you safe when reading around:

• Match the trial name to the population. OSA means sleep apnoea. Other trials cover other groups.
• Match the dose. A 15mg average is not a 5mg average.
• Match the duration. Results at different time points are not interchangeable.
• Never set the numbers from separate trials side by side as if they were a head-to-head contest.

SURMOUNT-5 is the first large head-to-head trial of tirzepatide and semaglutide for weight loss. In that trial, adults took tirzepatide or semaglutide 2.4mg for 72 weeks, and average loss was 22.8 kg on tirzepatide against 15.0 kg on semaglutide.¹⁵ That is a separate population from sleep apnoea.

05 · Weight loss and sleep apnoea

Does sleep apnoea go away with weight loss?

For some people sleep apnoea improves with weight loss, but whether it resolves depends on the person, and a sleep clinician is the right judge. SURMOUNT-OSA looked at exactly this relationship, measuring how breathing disruptions changed alongside weight.¹⁶

Our AHI reduction guide explains the breathing index.

Practical points if you have sleep apnoea:

• Keep using prescribed breathing equipment until your sleep team advises otherwise.
• Ask for a repeat sleep assessment if your weight changes significantly.
• Tell the prescriber about your sleep apnoea during any weight-loss consultation.

06 · Pace and review

Pace of results and what a review looks like

Weight loss on Mounjaro is gradual by design. The first weeks on 2.5mg are an adjustment phase and losses are usually modest; most measurable progress builds from 5mg onward, month by month.

Everyone starts on 2.5mg once a week. After at least 4 weeks the dose increases to 5mg, and can then step up by 2.5mg at a minimum of 4-week intervals up to a maximum of 15mg weekly, depending on how you respond and tolerate it. Many people settle at a maintenance dose of 5mg, 10mg or 15mg — higher is not automatically better.

Your prescriber reviews response over time. If you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, your prescriber will discuss whether continuing or stopping is right for you. Think in months, not days, and judge progress by trend rather than individual weigh-ins.

07 · Safety and side effects

Safety and side effects to know about

Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle. Serious side effects are uncommon but need urgent attention. Seek immediate medical help for: severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. For anything else that worries you, speak to your prescriber.

You can report any suspected side effect through the MHRA Yellow Card scheme.¹⁹ You can read more in our Mounjaro adverse events guide.

Mounjaro (tirzepatide) is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. Individual results vary. This page is information, not a substitute for medical advice.

08 · Getting access

Getting access on the NHS or privately

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

Privately, our service starts with a free online consultation reviewed by a GPhC-registered prescriber. We supply genuine KwikPens through official LillyDirect supply, with free next-day tracked delivery in temperature-controlled packaging. All six doses are in stock, and same-day dispatch applies when you order by 3pm. Ongoing monthly clinical reviews are included.