GLP-1 vs GLP-2: What's the Difference? (October 2026)

01 · The short verdict

GLP-1 vs GLP-2: which one is relevant to weight loss?

For weight management in the UK, the relevant medicines are the GLP-1 ones. Mounjaro (tirzepatide) activates both GIP and GLP-1 receptors, and Wegovy (semaglutide) is a single-action GLP-1 medicine.¹ Our guide to GLP-1 and GLP-2 drugs covers the wider families of medicines.

The question is therefore rarely GLP-1 against GLP-2. It is usually Mounjaro against Wegovy, or a licensed prescription against an unregulated product sold under a confusing name. Both Mounjaro and Wegovy are effective, licensed treatments. Which suits you depends on your health profile, how you tolerate treatment and your prescriber's advice, not on the headline number alone.¹⁵

Who each option suits. Mounjaro suits adults whose prescriber recommends the dual GIP and GLP-1 action and a once-weekly pen with six strengths. Wegovy suits adults whose prescriber prefers a single-action GLP-1 medicine with its own dose ladder. A GLP-2 product is not something we can recommend or supply, so if you are considering one, speak to a specialist.

02 · Side by side

Comparison table: GLP-1/GIP, GLP-1 and GLP-2

The trial results in this table come from different trials in different populations, so do not read the Mounjaro and Wegovy rows as a direct contest. Only SURMOUNT-5 compared the two medicines head to head.

03 · Deciding

Decision factors if you want a weight-loss injection

If weight loss is your goal, these are the factors that matter. First, the licence: choose a medicine licensed for weight management in the UK, and take it only after a consultation. Second, the evidence: use trial-named figures, not marketing claims. Third, tolerance and your health history, which a prescriber reviews with you. Fourth, cost over a year, because both injections are ongoing treatments rather than one-off purchases.

Treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.² If you are ready to start, you can start your free consultation, and a GPhC-registered prescriber will review your answers. You can also see the Mounjaro pen prices and consultation; all six doses are in stock.

New customers save £40 on their first order with code FIRST40, and an automatic £25 reorder discount applies to every future order (code DOSE25). The consultation is free and the price shown is the price paid.

Related guide: Ozempil glp-1.

Related guide: Wat is glp-1.

04 · What GLP-1 means

What GLP-1 means for weight-loss medicines

GLP-1 is a natural gut hormone, and several UK weight-loss medicines are built around its receptor. Mounjaro (tirzepatide) is a once-weekly injectable prescription medicine made by Eli Lilly. It is licensed in the UK for weight management in adults and for type 2 diabetes.¹

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 In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.

Semaglutide, the medicine in Wegovy and Ozempic, is described as a single-action GLP-1 medicine.¹

The pen is a pre-filled multi-dose KwikPen. It comes in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹

One practical point on timing: tirzepatide has a half-life of about five days. After a final dose it takes roughly 4 to 5 weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹

Because the names are so similar, people often assume GLP-1 and GLP-2 are interchangeable. They are not.

The takeaway: when a product is described as a GLP-1 medicine, it matters which receptors it acts on, because that determines both what it is licensed for and what evidence exists for it.

05 · Where GLP-2 fits

Where GLP-2 fits

For a GLP-2 product, questions about whether it is better or worse than a GLP-1, whether it is safe or whether it helps with weight loss belong with a specialist. Treat any claim that a GLP-2 peptide is a weight-loss shortcut with caution.

It is worth being sceptical of dramatic weight-loss claims on any product, particularly products sold under names that borrow the credibility of GLP-1 medicines. Mounjaro activates GIP and GLP-1 receptors.¹ If you see Mounjaro, semaglutide or tirzepatide marketed as a GLP-2, that is a red flag about the seller.

Our page on GLP-2 and tirzepatide covers this naming mix-up in more detail, and the overview of GLP-1 and GLP-2 drugs sets out how the terms are used.

If you have a bowel or digestive condition and have been told about a GLP-2 treatment, that is a conversation for your gastroenterologist or specialist team, not an online weight-loss service. They know your diagnosis and can explain what is appropriate.

If you notice any new symptom while taking any medicine, tell your prescriber. You can also report suspected side effects through the MHRA Yellow Card scheme.¹⁹ Reporting helps regulators monitor medicines, and it applies to licensed products and to anything you suspect is counterfeit.

06 · Mounjaro's dual action

Mounjaro's dual action: GIP plus GLP-1

The feature that sets Mounjaro apart is that it activates two receptors, not one. Tirzepatide is described as the first treatment of its kind to activate both GIP and GLP-1 receptors at once.¹ That dual action is what distinguishes it from single-action GLP-1 medicines such as semaglutide.

It is easy to confuse this with a GLP-1/GLP-2 combination. It is not one. The two receptors involved are GIP and GLP-1. Mounjaro is not a dual GLP-1 and GLP-2 agonist; it acts on GIP and GLP-1.

Together, the two receptor actions help regulate appetite, slow how quickly the stomach empties, and improve how the body responds to insulin.¹ People typically describe the outcome as feeling full sooner and being less hungry between meals, which makes a reduced-calorie diet easier to follow.

This is also why the comparison with Wegovy is meaningful. Both medicines act on the GLP-1 receptor, but only tirzepatide adds GIP. Whether that extra action matters for you depends on your own response, which is why a prescriber reviews your history before recommending a medicine and dose.

The dose ladder reflects this too. Mounjaro comes in six strengths from 2.5mg to 15mg, with at least 4 weeks on each dose, depending on how you respond. A first-order 2.5mg starter pen costs £129.99 with code FIRST40 (standard price £169.99). You can view the full range on the Mounjaro pen page.

If you are weighing the GLP-1 pathway against alternatives you have read about online, the key point is evidence. The dual-action design of tirzepatide has been tested in large trials. Pathways without that evidence base should not be treated as equivalents, whatever the product name suggests.

Finally, remember that mechanism does not equal outcome. Two people on the same dose can respond differently, and treatment works alongside diet and activity changes, not in place of them.

07 · Trial results

What the trials show for GLP-1 medicines

Weight-loss figures for these injections come from named trials, and they are averages. In SURMOUNT-1, which enrolled 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

These are trial averages, and individual results vary. For a worked example, someone starting at 100 kg would lose about 21 kg at the 20.9% average, but that is arithmetic on an average, not a prediction for any one person.

The same trial reports how many people hit 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

For semaglutide, the STEP 1 trial found that adults on 2.4mg (Wegovy) lost on average 14.9% of body weight over 68 weeks, compared with 2.4% on placebo.⁹

Please avoid setting SURMOUNT-1 and STEP 1 side by side as if they were a contest. They were separate trials with different designs, so only a head-to-head trial can compare the medicines directly.

If a website offers a specific percentage for a GLP-2 peptide, ask which trial it comes from, who ran it and where it was published. A credible claim will name all three.

Finally, keep expectations realistic. The trials paired the medicine with a reduced-calorie diet and more physical activity. The injection is a support for those changes, and trial averages do not predict your own result.

08 · Mounjaro vs Wegovy

Mounjaro vs Wegovy: the head-to-head evidence

If you are comparing GLP-1 medicines, SURMOUNT-5 is the relevant head-to-head trial. In this first large head-to-head trial, adults on tirzepatide lost on average 20.2% of body weight over 72 weeks, versus 13.7% on semaglutide 2.4mg (Wegovy).¹⁵ Both are effective, licensed treatments.

The trial supports a direct comparison, but it does not settle the choice for you. Which suits you depends on your health profile, tolerance and prescriber advice, not the headline number alone. A medicine that you tolerate and can stay on may do more for you than one with a bigger average on paper.

Dosing differs as well. Wegovy comes as pens of 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg once weekly. It steps up after 4 weeks on each of 0.25mg, 0.5mg, 1mg and 1.7mg, and the 2.4mg maintenance dose starts from week 17; 2.4mg is the licensed maintenance dose for weight management.¹⁸ Mounjaro has six strengths from 2.5mg to 15mg.¹

On cost, a first Wegovy pen is £99.99 (first order), and a first Mounjaro 2.5mg pen is £129.99 with code FIRST40 (standard price £169.99). You can see Wegovy on the Wegovy pen page. For availability of either, check at the time of order.

Many readers ask whether moving between the two is possible. That is a prescriber decision. The prescriber decides when to switch and which dose to start on, and Wegovy's licensed dose ladder starts at 0.25mg.

Neither medicine is a GLP-2. If a price comparison or ad for a product claims to be a cheaper GLP-2 alternative to Mounjaro or Wegovy, ask what it contains, who supplies it and whether it is licensed in the UK. For a wider view of the options, see all weight loss treatments.

09 · NHS vs private

NHS vs private access to GLP-1 treatment

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.⁴ The NHS primary-care rollout began in June 2025 with the highest-need groups first, initially BMI 40+ with four or more qualifying conditions.⁶

Full rollout is expected to take years. That is why many people who meet the licensed criteria choose regulated private treatment rather than waiting. If you think you may qualify on the NHS, ask your GP first. It costs nothing to find out where you stand.

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

The private route works differently. You complete a free online consultation, and a GPhC-registered prescriber reviews it. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. The consultation is free, with no obligation.

Whichever route you choose, the same principle applies: GLP-1 medicines are prescription-only. Anyone offering to supply without a consultation or prescription is not operating within the regulated system, and that applies equally to products marketed as a GLP-2.

Private treatment also includes aftercare. Ongoing monthly reviews, dose titration and follow-up assessments are handled by the prescribing team, with side-effect support. Repeat orders re-check suitability, and there is no auto-shipping.

If you are not sure which route fits, the weight loss treatments hub sets out the options, and you can begin a free consultation whenever you are ready.

10 · Cost over a year

What GLP-1 treatment costs over a year

Both injections are ongoing treatments, so total cost over the treatment period matters as well as the starter price. The standard price of one Mounjaro pen (4 weeks) is £169.99 at 2.5mg, £218.99 at 5mg, £279.99 at 7.5mg, £290.99 at 10mg, £319.99 at 12.5mg and £329.99 at 15mg. These are standard prices before any discount.

If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard prices. A first year (13 pens) 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. For other maintenance doses, use the monthly price for that dose.

Discounts reduce these figures. A new customer's first order is £40 less with code FIRST40, and every later order is £25 less (code DOSE25). If you switch to us at 15mg, your first order is £289.99.

Payment options include Visa and Mastercard, Klarna and pay-monthly options. There are no subscriptions, so you only pay for the orders you place.

If you see a GLP-2 peptide advertised at a low price, remember that cost is not the main issue; supply source and licensing are. A low price from an unverified seller is a risk, not a saving.

For Wegovy, the first pen is £99.99 (first order).

11 · Buying safely

Buying GLP-1 medicines safely and how ordering works

Buy only from a pharmacy that appears on the GPhC register. Ours is GPhC-registered (9012878), and you can check any pharmacy on the public register.¹² This matters because counterfeit weight-loss pens exist, and the MHRA publishes counterfeit medicine alerts.⁷

Warning signs include a seller offering to supply without a consultation or prescription, dramatic weight-loss claims, and products labelled with the wrong hormone. If something is sold as a GLP-2 weight-loss product, ask what it contains and whether it is licensed in the UK. Report suspected problems through the Yellow Card scheme.¹⁹

Our Mounjaro supply is official LillyDirect supply: genuine KwikPens direct from Eli Lilly's UK distribution, with all six doses stocked from 2.5mg to 15mg. Delivery is free next-day tracked (DPD, temperature-controlled packaging, discreet), with same-day dispatch when ordered by 3pm. Saturday delivery is £14.99.

How ordering works:

• Complete the free online consultation, a short health questionnaire with no charge or obligation.
• A GPhC-registered prescriber reviews it. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.
• Our registered pharmacy dispenses and dispatches, and your order arrives next day. Needles, a sharps bin and injection guidance are included.

Support is available Monday to Friday, 9am to 5pm, by email at support@everydaymeds.co.uk, account portal chat or phone on 0333 207 0413. The free GLPTrackr app helps you track your GLP-1 journey on iOS and Android.

Dispensed prescription medicines cannot be returned except faulty, damaged or wrong items, which must be reported within 3 days. Refunds take 5 to 10 working days. Ready to begin? Start your free consultation.

12 · 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

13 · Questions for your prescriber

Questions to ask a prescriber before choosing

A few well-chosen questions help you settle the choice with your prescriber. Mounjaro 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, and individual results vary.

Start with licence and fit. Ask whether the medicine is licensed in the UK for weight management and whether it suits your health history. Mounjaro and Wegovy are both licensed for that purpose, and your prescriber can explain which suits you.

Next, ask about your starting dose and how it will change. Mounjaro begins at 2.5mg, and Wegovy at 0.25mg. Wegovy steps up after at least 4 weeks to reach 2.4mg from week 17.¹⁸ Your prescriber sets the pace for Mounjaro, with at least 4 weeks on each dose, depending on how you respond.

Ask about what to expect from treatment. Trial averages, such as 20.9% on 15mg in SURMOUNT-1, are not a promise of your own result.² A prescriber who frames them as averages is being straight with you.

Ask what to do if something feels wrong. New symptoms should be discussed with your prescriber, and you can report side effects through the Yellow Card scheme.¹⁹ Read the patient information leaflet that comes with your pen too.¹³

If you are on other medicines, tell the prescriber everything you take, including any peptide or supplement bought online. They can only advise on what they know about.

Finally, if you have read about a GLP-2 product and are curious, say so. A prescriber can tell you plainly whether it is relevant to you, and can point you to the right specialist if it is.

Our guide to Trapezoid GLP-1 shows how confusing terminology leads people astray, and it is a useful reminder to check names against the product's licence.