Ozempic Switch to Mounjaro: How It Works in the UK (October 2026)

01 · The short verdict

Should you switch from Ozempic to Mounjaro?

Switching suits people whose prescriber agrees tirzepatide is a better fit than semaglutide for their goals, health profile or tolerance. It is a prescriber decision, not a DIY one. Both medicines are effective, licensed treatments, and neither is right for everyone.

The most common reason people ask is weight loss. Here the licensing point matters: Ozempic is semaglutide licensed for type 2 diabetes. It is not a UK weight-loss medicine, and prescribing it privately for weight loss is off-label.¹ The licensed weight-management options are Mounjaro (tirzepatide) and Wegovy (semaglutide 2.4mg). So for weight loss, a regulated UK pharmacy will not supply Ozempic, and "Ozempic or Mounjaro" is really "Wegovy or Mounjaro".¹⁸ Our guide to the differences between Mounjaro and Ozempic goes further on this.

If you take Ozempic for type 2 diabetes, Mounjaro is also licensed for that condition.¹ Any change should involve whoever manages your diabetes, because other medicines you take may need reviewing.

02 · Side by side

Ozempic, Wegovy and Mounjaro compared

The table sets out what each medicine is and how it is used. Trial results come from different studies, so only the SURMOUNT-5 row is a direct head-to-head comparison.

The trial figures are averages, individual results vary, and treatment works alongside a reduced-calorie diet and more physical activity.¹⁵²⁹

03 · Deciding

What to weigh before you switch

Four questions help most. Each is worth raising with your prescriber.

• Why are you considering it? Slower progress, side effects you find hard to tolerate, or a wish for the dual-action option are all fair reasons to discuss a change. Your prescriber can tell you whether they point towards switching.
• What licence applies? If Ozempic was prescribed for diabetes, that is a separate decision from starting a weight-management medicine.
• What does it cost? Mounjaro is £169.99 per month at the 2.5mg starting dose, rising with each strength. Our price comparison of Mounjaro and Ozempic has the detail, and the Mounjaro pen page shows live prices at every dose.
• Are you comfortable with the process? A switch involves a gap, a restart on a lower dose and a gradual step-up. It is not instant.

New customers save £40 on their first order at any dose with code FIRST40, and an automatic £25 reorder discount applies to every future order (code DOSE25). All six doses are in stock.

04 · How a supervised switch works

How a supervised switch from Ozempic to Mounjaro works

There is no licensed direct conversion between semaglutide and tirzepatide, so a prescriber builds the plan around you.¹ The milligrams of the two medicines do not map onto each other.

In practice, switching is done under prescriber supervision in three parts:

• Stop the previous medicine. Your last Ozempic dose is taken as your prescriber directs, and no more are taken after that.
• Observe a washout interval. Your prescriber decides how long to leave between the last dose of the old medicine and the first dose of Mounjaro.
• Start Mounjaro at a suitable dose. This is often the 2.5mg starting dose, sometimes adjusted based on your history.¹¹

If you have a plan from a previous prescriber, bring it to the consultation. Our related guide on whether you can change from Ozempic to Mounjaro covers the same question from another angle.

Our free consultation asks about the medicine you currently take, your dose and when you last injected. A GPhC-registered prescriber reviews your answers and decides whether Mounjaro is suitable and which dose to begin with. Tell your prescriber if you use the oral contraceptive pill: Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed. Switch to a non-oral method, or add a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.

05 · Never run two together

Why you should never take both medicines together

Mounjaro must not be combined with other GLP-1 medicines, and that includes Ozempic and Wegovy.¹ Running two GLP-1 medicines together is exactly what a supervised switch is designed to avoid.

The same warning covers unlicensed "research" peptides, such as retatrutide, which has no UK licence, and compounded copies. These combinations have no safety data and no regulated supply chain.¹ If a seller promises faster results outside a licensed pathway, treat that as the warning sign.

If you still have unused Ozempic pens, do not keep injecting from them "just in case" once you have started Mounjaro. Ask your prescriber or pharmacist what to do with them.

06 · Starting dose and step-up

Which Mounjaro dose will you start on?

Most people start on the 2.5mg pen, though your prescriber may adjust this based on your history. Mounjaro comes as a pre-filled multi-dose KwikPen in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg, taken once a week.¹

Being on a high dose of Ozempic does not automatically mean a high dose of Mounjaro. A lower start gives your prescriber a chance to see how you tolerate tirzepatide before stepping up.

07 · Evidence compared

What the trials say about tirzepatide and semaglutide

SURMOUNT-5 is the first large head-to-head trial of the two, and it favoured tirzepatide on average weight loss. In it, 751 adults took tirzepatide or semaglutide 2.4mg (Wegovy) for 72 weeks. Average loss was 20.2% of body weight on tirzepatide versus 13.7% on semaglutide, or 22.8 kg versus 15.0 kg.¹⁵ For someone starting at 100 kg, 20.2% is about 20 kg.

The trial also reported how many people reached each threshold:

Both are effective, licensed treatments. Which suits you depends on your health profile, tolerance and prescriber advice, not the headline number alone.¹⁵ These are trial averages, so they do not predict your own result.

For context from separate trials, STEP 1 found adults on semaglutide 2.4mg lost on average 14.9% of body weight over 68 weeks, compared with 2.4% on placebo.⁹ In SURMOUNT-1, 2,539 adults on tirzepatide alongside diet and exercise lost on average 15% on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, versus 3.1% with lifestyle changes alone.² Those two trials were run separately, so do not read them against each other as a direct comparison.

08 · Side effects and tolerance

Side effects when changing medicine

Many people switch because of how they tolerate their current medicine, so it helps to know what the evidence says. In STEP 1, gastrointestinal side effects were reported by 74.2% of people on semaglutide 2.4mg, compared with 47.9% on placebo. 7.0% stopped treatment because of side effects, compared with 3.1% on placebo.⁹

Starting a new medicine means your body adapts again, which is another reason prescribers start low. Common side effects and what to do about them are listed in the patient information leaflet that comes with the pen, and our team offers side-effect support as part of ongoing monthly reviews.

If you notice a new symptom after switching, discuss it with your prescriber. You can also report suspected side effects through the MHRA Yellow Card scheme.¹⁹

09 · NHS and private routes

NHS or private: where does the switch happen?

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. The NHS primary-care rollout began in June 2025 with the highest-need groups first, initially BMI 40+ with four or more qualifying conditions.⁴⁶ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

If you are on NHS-prescribed Ozempic for diabetes, speak to your GP or diabetes team before changing anything. If you already use a private provider and want to move pharmacy rather than medicine, see our pages on changing your Mounjaro supplier and switching Mounjaro provider on a private prescription. For the private prescription route, our Mounjaro and Ozempic private prescription guide explains what a regulated supplier will and will not prescribe.

10 · Serious side effects

Serious side effects: when to get help straight away

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. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹ Mounjaro must not be used during pregnancy, and it should be stopped at least one month before trying to conceive. If you become pregnant during treatment, stop the medicine and tell your prescriber promptly.

11 · Ordering with us

How ordering Mounjaro with us works

Ordering takes four steps and the consultation is free, with no obligation. The price shown is the price paid, with no hidden fees.

• Free online consultation. A short health questionnaire. Tell us which medicine you take now, your dose and when you last injected.
• Prescriber review. Your answers are reviewed by a GPhC-registered prescriber, not a scoring script. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.
• Dispensing and dispatch. Your pen is dispensed by our registered pharmacy, with same-day dispatch when ordered by 3pm.
• Delivery. Free next-day tracked delivery in discreet, temperature-controlled packaging. Saturday delivery is £14.99.

Our Mounjaro comes through official LillyDirect supply, direct from Eli Lilly's UK distribution, as genuine KwikPens. Needles, a sharps bin and injection guidance are included with every order. Repeat orders re-check suitability, and there is no auto-shipping. You can pay by Visa, Mastercard or Klarna, with pay-monthly options and no subscriptions. Start with the free consultation or view the Mounjaro pen.

Wondering how Wegovy compares on cost? Its first pen is £99.99 as a first-order price; see the Wegovy pen. For wider options, including the new GLP-1 tablets, browse all weight loss treatments.

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.