Which GLP-1 Is Best for Weight Loss? UK Options (October 2026)

01 · The short answer

Which GLP-1 is best for weight loss?

Mounjaro and Wegovy are both licensed for weight management, and a prescriber decides which suits you. Tirzepatide activates both GIP and GLP-1 receptors, which together help regulate appetite, slow how quickly the stomach empties and improve the way the body responds to insulin.¹ That dual action is what distinguishes it from single-action GLP-1 medicines such as semaglutide (Wegovy and Ozempic).¹

The best GLP-1 for you is the one that fits your health history, your other medicines, your side-effect tolerance and your budget. Wegovy is a licensed, once-weekly alternative, and some people do well on it or are steered to it by their prescriber. Daily liraglutide injections and the newer tablets suit people who prefer a different format.

Here is who each option tends to suit, in plain terms:

• Mounjaro (tirzepatide): adults who meet the licensed criteria and want a once-weekly pen with six strengths from 2.5mg to 15mg, giving room to adjust the dose gradually.
• Wegovy (semaglutide): adults who meet the criteria and whose prescriber prefers a single-action GLP-1, or who want a different medicine after a poor experience with another one.
• Liraglutide (Saxenda and similar): people who are happy with a daily injection rather than a weekly one.
• GLP-1 tablets: people who would rather not inject. See our guide to GLP-1 weight loss pills.

If you want the shortest path, start the free online consultation. A GPhC-registered prescriber reviews your answers and recommends the medicine that is suitable for you.

02 · Side by side

GLP-1 options compared: dosing, evidence and cost

Wegovy's dose steps up after 4 weeks on each of 0.25mg, 0.5mg, 1mg and 1.7mg, so the 2.4mg maintenance dose starts from week 17.¹⁸

03 · Cost and ordering

What a GLP-1 costs and how ordering works

The price of a GLP-1 is monthly, per four-week pen, and it rises with dose for Mounjaro. Your first 2.5mg pen costs £129.99 with code FIRST40; the standard price is £169.99. If you are switching to us at a higher dose, your first order at 15mg is £259.99. Every later order is £25 off the standard price (code DOSE25).

Across the UK pharmacies we track, the cheapest and dearest Mounjaro pens across all doses run from £143.96 to £319.99, and the gap between providers for the same dose ranges from £20 to £36.03 (checked 24 October 2026). That gap matters over a year, so compare the same dose before you choose.

If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £879.96 at standard prices. A first year costs £2,399.88 if you stay on 5mg after your 2.5mg starting pen, up to £3,279.88 if you step up through every dose to 15mg. A new customer's first order is £40 less, and every later order £25 less. For other maintenance doses, the monthly prices are £244.99 at 7.5mg, £274.99 at 10mg and £289.99 at 12.5mg. See the Wegovy pen page for current Wegovy pricing, and all six Mounjaro doses are in stock on the Buy Mounjaro page.

Ordering takes three steps:

• Free online consultation: a short health questionnaire, with no charge and no obligation.
• Prescriber review: reviewed by a GPhC-registered prescriber. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.
• Dispatch and delivery: dispensed by our registered pharmacy, with same-day dispatch when ordered by 3pm and free next-day tracked delivery in temperature-controlled packaging. Saturday delivery is £14.99.

04 · What the evidence shows

Mounjaro trial results (SURMOUNT-1)

In 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. The comparison group, using lifestyle changes alone, lost 3.1%.²

Those are trial averages, and individual results vary. Treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.² The averages do not predict your own result.

The same trial reported how many people reached key thresholds 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%.²

To put the percentage in context with a worked example: for someone starting at 100 kg, 20.9% is about 21 kg and 15% is about 15 kg. Your starting weight, dose, diet and activity all shape what actually happens.

05 · Mounjaro vs Wegovy

Mounjaro or Wegovy: how they differ

The core difference is mechanism: Mounjaro activates two receptors, GIP and GLP-1, while Wegovy's semaglutide activates one.¹ Both are once-weekly injections licensed for weight management in adults, and both are used alongside a reduced-calorie diet and increased physical activity.

Their dose structures differ too. Mounjaro comes in six strengths from 2.5mg to 15mg, and you and your prescriber decide when to step up. Wegovy has a set ladder of 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg, stepping up after at least four weeks and reaching the 2.4mg maintenance dose from week 17.¹⁸ The Mounjaro dose guide covers titration.

Which is safer? Both are licensed medicines with a full list of possible side effects in their patient leaflets, and neither is risk-free. Safety depends on your own health, so the answer comes from a prescriber's review of your medical history and current medicines, not from a league table.¹³ Whichever you take, report suspected side effects through the Yellow Card scheme.¹⁹

Many people also ask about switching. The prescriber decides when to switch and which dose to start on; Wegovy's licensed dose ladder starts at 0.25mg. Do not swap or guess doses yourself.

06 · Side effects and tolerability

Which GLP-1 has the fewest side effects?

Every GLP-1 medicine lists its own possible side effects in the patient information leaflet, and how you respond depends on your dose, your pace of increase and your own physiology.¹³

Practical points that help in the real world:

• Read the leaflet for the medicine you are prescribed, and keep it to hand.
• Tell your prescriber about any new or worrying symptom rather than waiting for it to pass.
• Report suspected side effects through the MHRA Yellow Card scheme.¹⁹
• Use your monthly review to talk through tolerability before any dose change.

Our ongoing monthly reviews, dose-titration and side-effect support are included, so you are not left to work it out alone. If a dose does not suit you, your prescriber decides whether to hold, adjust or change medicine. Our guide on the best foods while on a GLP-1 covers eating habits that many people find helpful alongside treatment.

07 · Who cannot take GLP-1

Who cannot take a GLP-1 medicine?

Suitability is decided by a prescriber, not by a rule of thumb. You should not take Mounjaro if you are allergic to tirzepatide or any of its ingredients, and it should not be used during pregnancy or while trying to conceive. Mounjaro must not be used during pregnancy, and it should be stopped at least one month before trying to conceive. Your prescriber will take extra care, or may recommend against treatment, if you have a history of pancreatitis, severe gut or digestive disease, diabetic retinopathy, or gallbladder problems. Mounjaro is licensed for weight management in adults with a BMI of 30 or above, or a BMI between 27 and 30 with at least one weight-related condition such as high blood pressure, high cholesterol, obstructive sleep apnoea, cardiovascular disease, prediabetes or type 2 diabetes. It must be used alongside a reduced-calorie diet and increased physical activity.¹

A prescriber will assess your BMI, medical history and current medicines before deciding whether it is suitable. Some groups are advised not to use these medicines or need extra care; the full list is in the patient information leaflet and the SmPC, so read both and be open with your prescriber.¹³

Two interactions are worth knowing about. 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 If you take insulin or sulfonylureas, doses may need adjusting because of the risk of low blood sugar; that is a conversation for your prescriber, and no one should change those doses alone.¹³

This is exactly why our consultation is reviewed by a GPhC-registered prescriber, and why repeat orders re-check suitability. Nothing ships automatically.

08 · NHS or private

NHS or private: how to get a GLP-1 in the UK

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.

If you are checking whether you may qualify on the NHS, ask your GP first. If you choose private treatment, make sure the supplier is a regulated pharmacy. You can check ours on the GPhC register (registration 9012878).

09 · Pills and supplements

The best weight loss pill, and the 'poor man's Ozempic'

No supplement is a GLP-1 medicine, and no single weight loss pill suits everyone. Prescription GLP-1 tablets exist, including Wegovy tablets and Foundayo. They are separate medicines with their own dosing, eligibility checks and trial results, and no trial has compared Mounjaro directly with either tablet. Our guide to GLP-1 pills for weight loss goes through them.

The phrase 'poor man's Ozempic' or 'nature's Ozempic' is marketing, usually applied to berberine and similar products. These are low-cost supplements with no clinical oversight and no standardised dosing. Be sceptical of dramatic weight-loss claims on any supplement label.

Be careful with sellers offering to supply a prescription GLP-1 without a consultation or prescription. Counterfeit and unregulated products are a real risk. Our Mounjaro is genuine KwikPens supplied through official LillyDirect supply direct from Eli Lilly's UK distribution. The MHRA publishes counterfeit medicine alerts.⁷

10 · New drugs and stopping

Are there newer options, and what happens if you stop?

Medicines still in development, such as retatrutide, are not licensed in the UK, so they cannot be prescribed here and you should be wary of anyone selling them. Our guide to which GLP-1 is approved for weight loss lists the licensed options.

If you stop Mounjaro, the medicine leaves your body gradually. 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

In SURMOUNT-4, people who stopped tirzepatide after 36 weeks regained on average 14% of body weight over the following year, while those who continued treatment lost a further 5.5% on average. Stopping should always be planned with your prescriber, with diet and activity habits ready to carry the load. Treatment works alongside a reduced-calorie diet and increased physical activity, so the habits you build during treatment matter.

Some people ask whether one GLP-1 is better for conditions other than weight, such as inflammation. For that question, see which GLP-1 is best for inflammation and ask your prescriber.

11 · 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