Mounjaro Switch: How to Switch GLP-1 Medicines Safely (October 2026)

01 · The short answer

Switching to or from Mounjaro: the verdict up front

Switching between GLP-1 medicines is routine for prescribers, but it is never a like-for-like swap. There is no licensed direct conversion between semaglutide and tirzepatide. Switching is done under prescriber supervision: the previous medicine is stopped, a washout interval is observed, and the new medicine starts at a dose your prescriber judges appropriate, often the lowest starting dose and sometimes adjusted based on your history.¹¹¹

Who each direction tends to suit, in plain terms:

• Wegovy or Ozempic to Mounjaro: suits people who want the dual-action option, or who have plateaued or not tolerated semaglutide and whose prescriber agrees a change is reasonable. Our guide to switching from Ozempic to Mounjaro goes through it step by step.
• Mounjaro to Wegovy: suits people who have not tolerated tirzepatide, or who prefer semaglutide on prescriber advice. See how a Mounjaro to Wegovy switch works.
• One pharmacy to another, same medicine: suits people who simply want a different supplier. The medicine and dose stay the same; the prescriber reviews you afresh.

Both Mounjaro and Wegovy are effective, licensed weight-management treatments. Which suits you depends on your health profile, tolerance and prescriber advice, not the headline number alone.¹⁵

02 · Side by side

Mounjaro vs Wegovy: what changes when you switch

The table sets out the facts that matter when you move between the two licensed weight-management injections. The trial figures come from different studies except SURMOUNT-5, which is the first large head-to-head comparison.

Trial averages do not predict your own result, and the two medicines were studied in different trial populations apart from SURMOUNT-5. Treat the table as context for a conversation with your prescriber, not a verdict on what will happen to you.

03 · Deciding

The decision factors that actually matter

The first factor is why you are switching. Tolerability and a stalled result are legitimate reasons to talk to your prescriber; a promise of faster results is not. If something promises faster results outside a licensed pathway, that is the warning sign.¹

The second is timing. Tirzepatide has a half-life of about five days, so after a final dose it takes roughly 4–5 weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹ Your prescriber decides the washout interval and the date of the first dose of the new medicine.

The third is the starting dose. Because there is no conversion, do not expect to carry your old dose across. A higher dose of one medicine does not translate into a matching dose of the other, and your prescriber may restart at the lowest strength.

A new customer gets £40 off a first order at any dose with code FIRST40, and every later order is £25 off the standard price (code DOSE25). You can see the Mounjaro pen prices and consultation on the product page; all six doses are in stock.

04 · Ozempic to Mounjaro

Can you switch from Ozempic to Mounjaro?

Yes, you can switch from Ozempic to Mounjaro, but only under prescriber supervision, because there is no licensed direct conversion between semaglutide and tirzepatide.¹ Typically Ozempic is stopped, a washout interval is observed, and Mounjaro begins at a dose your prescriber judges appropriate. That is often the 2.5mg starting dose, sometimes adjusted based on your history.¹¹

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. The licensed weight-management options are Mounjaro (tirzepatide) and Wegovy (semaglutide 2.4mg), so a regulated UK pharmacy will not supply Ozempic for weight loss.¹ If you currently have Ozempic for diabetes, your diabetes team should be told before any change.

People often ask how Ozempic works. It is a single-action GLP-1 medicine, whereas tirzepatide activates two natural gut-hormone receptors at once, GIP and GLP-1. Together these help regulate appetite, slow how quickly the stomach empties and improve the way the body responds to insulin.¹ Most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.

For a fuller walk-through of the Ozempic pathway, including comparing your options, read switching Ozempic to Wegovy or Mounjaro.

05 · Mounjaro to Wegovy

Steps for switching from Mounjaro to Wegovy

Switching from Mounjaro to Wegovy is planned by your prescriber, who decides when you switch and which dose you start on. The practical steps are these.

• Step 1: Say why. Tell your prescriber what is driving the change, such as side effects, a stalled result or a preference.
• Step 2: Agree the last Mounjaro dose. Your prescriber confirms when to take your final injection. Tirzepatide takes roughly 4–5 weeks to clear, and nothing needs doing while it does.¹
• Step 3: Wait for your start date. Your prescriber decides when you start Wegovy, so follow their instruction.
• Step 4: Start Wegovy at the dose you are given. The Wegovy ladder runs 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg, stepping up after at least 4 weeks and reaching the 2.4mg maintenance dose from week 17.¹⁸ Whether you begin at the bottom of that ladder is your prescriber's call.
• Step 5: Do not overlap. Never run two GLP-1 medicines together.¹

A common worry is whether a high Mounjaro dose such as 5mg translates to a particular Wegovy strength. It does not, because there is no conversion. Our page on a 5mg Mounjaro switch to Wegovy covers that case, and the main guide to moving between Wegovy and Mounjaro covers the other direction.

Wegovy results differ by person. In STEP 1, adults on semaglutide 2.4mg lost on average 14.9% of body weight over 68 weeks, compared with 2.4% on placebo.⁹ As a worked example, for someone starting at 100 kg, 14.9% is about 15 kg. Individual results vary, and that figure is a trial average, not a timeline or a target.

06 · Other GLP-1 switches

How to switch GLP-1 medicines: Saxenda, Rybelsus, Trulicity and tablets

How to switch GLP-1 medicines depends on what you are leaving, but the rule is constant: your prescriber plans it, and you never combine two GLP-1 medicines.¹ The table gives a route map; each row links to a guide where one exists.

On tablets: there is no tablet form of Mounjaro, because tirzepatide is injection-only in the UK. Two GLP-1 weight-loss tablets are now licensed: Wegovy tablets (oral semaglutide, approved by the MHRA in June 2026) and Foundayo (orforglipron, approved in August 2026). They are different medicines from Mounjaro, with their own dosing, eligibility checks and trial results, and both are prescription-only.²⁰²¹ See our weight loss treatments hub for current options and prices.

Other licensed options work differently again: orlistat is a tablet that blocks some dietary fat absorption and produces smaller average losses. "Natural GLP-1" supplements such as berberine are not medicines, are not regulated for this use and have no comparable trial evidence.¹

07 · Washout and timing

Washout, timing and your injection day

The washout is the gap between your last dose of the old medicine and the first dose of the new one, and your prescriber sets its length. Follow your prescriber's instruction rather than a figure you saw online. Tirzepatide has a half-life of about five days and takes roughly 4–5 weeks to clear after a final dose.

Timing matters when you are switching to Mounjaro, too. Once you start, you inject once a week, on the same day each week, at any time of day, with or without food.¹ There is no best time of day. Many people choose a weekend morning so early side effects fall on days off.

If you need to change the weekly day later, you can, as long as at least 3 days (72 hours) have passed since your last dose.¹ If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time. If more than 4 days have passed, skip it and take the next on your normal day, and never take two doses within 3 days of each other.¹³

Do not try to "stretch" or split doses to bridge a gap between medicines. Altering doses outside the licence means unknown dosing accuracy and no safety data.

08 · Starting dose and pace

What to expect after switching to Mounjaro

After a switch, expect an adjustment phase, not instant results. Everyone starting Mounjaro in the licensed way begins on 2.5mg once a week, and that dose is about letting your body adjust rather than weight loss itself. After at least 4 weeks the dose rises to 5mg, then can step up by 2.5mg at a minimum of 4-week intervals (7.5mg, 10mg, 12.5mg) to a maximum of 15mg, depending on response and tolerance.¹¹¹

If your prescriber starts you above 2.5mg because of your history, that is their clinical judgement, not an entitlement to ask for. Higher is not automatically better, and many people settle at 5mg, 10mg or 15mg.¹

In SURMOUNT-1, adults taking tirzepatide alongside diet and exercise lost on average 15% of body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, versus 3.1% with lifestyle changes alone.² As a worked example, for someone starting at 100 kg, 20.9% is about 21 kg. These are trial averages, individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity.

The first weeks bring varied experiences. Some people notice an appetite change in week one, others little until a higher dose, and both are normal. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹ Progress is reviewed: 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.¹

Planning cost? If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard prices, and a new customer's first order is £40 less. A first year costs £2,711.88 if you stay on 5mg after your 2.5mg starting pen, up to £3,599.88 if you step up through every dose to 15mg, before discounts, with every later order £25 less.

09 · Changing pharmacy

Switching your Mounjaro to a different pharmacy

Moving your Mounjaro supply to a new pharmacy is the easiest kind of switch, because the medicine does not change. You still need a fresh consultation reviewed by a GPhC-registered prescriber, and they will want to know your current dose and when you last injected.

Switching at a higher dose is allowed. A new customer gets £40 off their first order at any dose with code FIRST40, including people moving from another provider at 15mg, where the first order is £289.99. After that, every future order gets an automatic £25 off (code DOSE25). Our own guide to switching your Mounjaro pharmacy and the switch provider page cover the practicalities.

Across the UK pharmacies we track, the cheapest and dearest Mounjaro pen at any dose range from £143.96 to £339.00 (index checked 10 October 2026). For the 2.5mg starting pen the range is £143.96 to £179.99, and the gap between providers for the same dose runs from £27 to £41. Boots' Mounjaro doses range from £179.00 to £339.00. Check what each provider's price includes before you decide.

What you can expect from us: a free online consultation with no charge and no obligation; a prescriber review, with payment taken when you order and a full automatic refund if the prescriber decides the treatment is not suitable; same-day dispatch when ordered by 3pm; and free next-day tracked delivery in temperature-controlled packaging. We supply Mounjaro through official LillyDirect supply, so these are genuine KwikPens. Ongoing monthly reviews are included. Start your free consultation to be assessed.

Store pens in the fridge at 2–8°C and never freeze them. Once in use, a pen can stay out of the fridge not above 30°C for up to 30 days, after which it should be discarded.¹ For an unopened pen that has been out of the fridge, check with the pharmacy and the patient information leaflet before using it.¹³

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

11 · NHS and safety

NHS access and staying safe when you switch

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.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. NHS access to Wegovy runs through specialist weight-management services; ask your GP.

Safety rules for any switch are short. Do not combine Mounjaro with other GLP-1 medicines, unlicensed "research" peptides such as retatrutide (which has no UK licence) or compounded copies. These combinations have no safety data and no regulated supply chain.¹ Only buy from a pharmacy you can find on the GPhC register; ours is 9012878. Avoid anyone offering to supply without a consultation or prescription.

Report any new or unexpected symptom to your prescriber, and to the MHRA through the Yellow Card scheme.¹⁹ If you take insulin or a sulfonylurea, doses may need adjusting because of the risk of low blood sugar, so tell your prescriber before switching. Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed.⁷ The SmPC advises switching to a non-oral method, or adding a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.¹

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.