GLP-1 Pros and Cons: An Honest UK Guide (October 2026)

01 · The short verdict

Are the pros of GLP-1 medicines worth the cons?

For many adults with obesity, yes, provided they are suitable and willing to change how they eat and move. The benefit is large on average, but it is not automatic, and it is not free of side effects or cost. The most useful way to judge is to see both columns side by side, then ask which of the cons would genuinely bother you.

Mounjaro (tirzepatide) is the medicine we supply. It is a once-weekly injection licensed in the UK for weight management and type 2 diabetes, and it activates both GIP and GLP-1 receptors. Other GLP-1 medicines, such as semaglutide, act on the GLP-1 receptor alone. Many of the general pros and cons apply across the class, and some are specific to tirzepatide.¹

02 · Your decision

The decisions you are actually facing

The first decision is whether you are the kind of person these medicines are for. 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. Individual results vary.¹

The second decision is how you would access it. The NHS route exists but is phased: 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 Many people who meet the licensed criteria choose regulated private treatment rather than waiting.

The third decision is whether the cons are manageable for you. If you want a broader view across the whole category, see the pros and cons of weight loss injections.

03 · Next step

If you are ready to see whether you qualify

You do not have to commit to anything to find out. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. Every strength is in stock, and your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99). You can start on the Mounjaro pen page, or read about our wider weight loss clinic first.

Related guide: Pros of mounjaro.

04 · What GLP-1 medicines are

What GLP-1 medicines are and how they work

GLP-1 medicines copy a natural gut hormone that helps regulate appetite and blood sugar. That one sentence explains most of both the pros and the cons, because the same actions that make you feel full also slow your digestion. Understanding the mechanism makes it much easier to judge what is a benefit and what is a trade-off.

Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine made by Eli Lilly. In the UK it is licensed for weight management in adults and for type 2 diabetes. It comes as a pre-filled multi-dose pen (KwikPen) in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹

Tirzepatide is the first treatment of its kind to activate 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. In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹

This dual action is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide, sold as Wegovy and Ozempic. The practical meaning for you is that the class shares a core set of effects, but the individual medicines differ in dosing, schedule and trial evidence. Which suits you depends on your health profile, tolerance and prescriber advice.

Different products, different schedules

Wegovy comes as once-weekly pens at 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg. Titration steps up after at least four weeks, reaching the 2.4mg maintenance dose from week 17. Mounjaro is also stepped up gradually, with treatment starting at the lowest strength and your prescriber reviewing the dose as you go.

Liraglutide, sold as Saxenda and in some other products, is supplied at a concentration of 6mg per millilitre and is a daily injection, unlike once-weekly Mounjaro and Wegovy. For some people a daily routine is a con; for others it is no problem at all. Which suits you is a conversation for your prescriber.

What the class is not

These are not stimulants, and they are not a shortcut that works without any change in how you eat. Treatment is licensed alongside a reduced-calorie diet and increased physical activity. If a seller suggests otherwise, treat that as a warning sign.

05 · The pros in detail

The pros of GLP-1 treatment in detail

The main pro is the size of the average weight loss seen in trials, delivered alongside diet and activity. This is the benefit most people come for, so it deserves a precise account rather than a headline.

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

It is also worth looking beyond the average. 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 That tells you most people in the trial saw a meaningful change, though not everybody lost the same amount.

Appetite and food noise

The day-to-day pro that many people notice is less hunger. Because the medicine helps you feel fuller sooner and less hungry between meals, a reduced-calorie diet stops feeling like a daily fight.

Blood sugar

Tirzepatide improves the way the body responds to insulin, which is part of why it is licensed for type 2 diabetes as well as weight management. If you have diabetes, your diabetes team will guide how it fits with your other treatment. If you take insulin or a sulfonylurea, doses may need adjusting to avoid low blood sugar, so tell your prescriber about everything you take.¹

A once-weekly routine

Mounjaro is a once-weekly injection, which many people find easier to maintain than a daily regime. A habit tied to one day of the week is simple to remember, and our free companion app, GLPTrackr, helps you track injections and progress on iOS and Android.

06 · The cons in detail

The cons of GLP-1 treatment in detail

The main cons are digestive side effects, the need to change how you eat, and the cost and commitment of ongoing treatment. None of these is a reason on its own to rule treatment out, but each deserves a clear-eyed look before you start.

Digestive effects

Because the medicine slows how quickly the stomach empties, food stays put for longer. Many people feel worse after very fatty, fried or very sugary food, and large portions sit heavily because the stomach empties more slowly. Smaller, slower meals work better.¹ Common effects include indigestion, reduced appetite, dizziness, reflux, burping, hair shedding and injection-site reactions, and the most common effects (more than 1 in 10 people) are nausea, diarrhoea, vomiting, constipation and abdominal discomfort. Side effects are most likely when starting treatment or moving up a dose, and for most people they ease within days to a few weeks as the body adjusts.¹³

Dehydration and the kidneys

Drinking enough matters more on Mounjaro than usual. Reduced appetite means less fluid from food, and vomiting or diarrhoea can dehydrate you quickly, which is the main route to the rare kidney problems reported with this class. If nausea or vomiting is persistent or you cannot keep fluids down, contact your clinical team — dehydration needs prompt attention.¹

Effects on other medicines

Because Mounjaro slows stomach emptying, it can affect how quickly some oral medicines are absorbed, particularly when you start treatment or increase the dose. Tell your prescriber about everything you take, especially warfarin or other narrow-margin medicines, insulin, or sulfonylureas, where doses may need reducing to avoid low blood sugar. No adjustment is needed for paracetamol.¹

Muscle loss

Some of any rapid weight loss comes from lean tissue, and protecting muscle protects your metabolism, strength and appearance. The two levers are adequate protein, with a protein source at every meal, which is harder when appetite is low, and resistance exercise on a regular weekly basis. This matters more, not less, as the dose rises and appetite falls.

Stopping treatment

Tirzepatide has a half-life of about five days, so after a final dose it takes roughly four to five weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears. Mounjaro manages weight; it does not cure the biology behind it. 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.

Reporting side effects

If you notice a new symptom that worries you, tell your prescriber. You can also report suspected side effects through the MHRA Yellow Card scheme.¹⁹

For a fuller list of drawbacks, see our dedicated page on the cons of GLP-1 drugs.

07 · Cost and access

Cost and access: NHS versus private

Cost is a genuine con, and the honest picture is that you can reach treatment through the NHS or privately, with a trade-off between wait and expense. Neither route is right for everyone, so it helps to understand both before choosing.

The NHS route

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). Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.⁴ If you think you might qualify, your GP is the person to ask. NHS access to Wegovy runs through specialist weight-management services; ask your GP.

The private route

Private treatment is a monthly cost, and it is worth planning it over a realistic timeline rather than looking only at the first pen. 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 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. A new customer's first order is £40 less, and every later order is £25 less.

For context, across the UK pharmacies we track, Mounjaro pens ranged from £143.96 to £339.00 per month at the time of our index check on 10 October 2026. The gap between providers for the same dose varied from £27 to £41.

What the price includes

Our consultation is free, and the price shown is the price paid, with no hidden fees. Delivery is free next-day tracked, in temperature-controlled packaging, with same-day dispatch when ordered by 3pm. Needles, a sharps bin and injection guidance are included with every order, and ongoing monthly reviews by the prescribing team are part of the service. You can pay by Visa, Mastercard or Klarna, and pay-monthly options exist, with no subscription. You can see current prices on the Mounjaro pen page, checked 10 October 2026.

Bundles

Some providers sell multi-month bundles. Whether those are a pro or a con depends on how sure you are about continuing, so read our page on Mounjaro bundles and their pros and cons before committing to more than one pen.

08 · Supplements and patches

GLP-1 supplements and patches: the pros and cons

Supplements marketed as natural GLP-1 boosters are not equivalents of prescribed GLP-1 medicines, and they should not be treated as substitutes.

No supplement is required with Mounjaro, but eating much less can leave gaps, so a standard daily multivitamin is a reasonable safety net while losing weight. Discuss anything beyond that with a pharmacist. Supplements sold as natural GLP-1 boosters are not equivalents and are not substitutes for prescribed treatment. Oral supplements, like other oral products, may be absorbed more slowly when you start treatment.¹

The honest pros

The pros of these products are small and mostly practical. They are low-cost, easy to buy without an appointment, and need no injection. For someone who is nervous about needles, that can feel appealing. That is the whole case in their favour.

The honest cons

The cons are bigger. They offer no clinical oversight, so nobody checks whether they suit you or interact with your other medicines. Dosing is not standardised, so you cannot compare one product with another. Dramatic weight-loss claims on packaging should be treated with suspicion.

Patches and similar products

Patches and other novelty formats are sold with similar promises. The same logic applies: a product that has not been through the licensing process for weight management is not the same thing as a licensed medicine. If you are curious about a particular format, our pages on GLP-1 supplements and the GLP-1 plaster take each one in turn.

A scam warning

Be wary of any seller offering to supply a prescription GLP-1 medicine without a consultation or prescription. Counterfeit medicines are a real risk, and the MHRA publishes counterfeit alerts and runs the Yellow Card scheme for reporting problems.⁷ A GPhC-registered pharmacy should be listed on the public register; ours is registered under GPhC 9012878, and we source Mounjaro through official LillyDirect supply direct from Eli Lilly's UK distribution.

09 · Living with treatment

Living with treatment: food, drink and movement

The cons of GLP-1 treatment are much easier to manage with a handful of daily habits.

What to eat and limit

No food is banned on Mounjaro, including bananas, but some choices make treatment easier and more effective. Prioritise protein at each meal, vegetables and fibre, and regular fluids. Many people feel worse after very fatty, fried or very sugary food, and large portions sit heavily because the stomach empties more slowly, so smaller, slower meals work better. Treatment is licensed alongside a reduced-calorie diet, so the aim is a sustainable deficit, not a perfect food list.¹

Protecting muscle

Aim to include a protein source at every meal, which is harder when appetite is low. Add resistance exercise on a regular weekly basis. This matters more as the dose rises and appetite falls.

Exercise

Increased physical activity is part of the licence, not an optional extra. Nothing special is required: the evidence-backed pattern is regular moderate activity, such as brisk walking, plus resistance work for muscle. Start where you are and build. On injection days with early side effects, lighter movement still counts.

Hydration

Keep water within reach through the day. Reduced appetite means less fluid from food, and any vomiting or diarrhoea can leave you dehydrated quickly.

Alcohol

There is no direct interaction between Mounjaro and alcohol, but drinking on a reduced appetite and an emptier stomach can hit harder than usual, and alcohol adds calories that work against your goals. If you also take insulin or a sulfonylurea, alcohol increases the risk of low blood sugar. Moderation is the sensible rule.

Coffee and caffeine

There is no interaction between Mounjaro and caffeine, so coffee and tea are fine. Strong coffee on an empty, slower-emptying stomach can aggravate nausea or reflux for some people, and high-calorie coffee drinks are an easy place for the calorie deficit to leak. Coffee rules circulating on social media have no clinical basis.

Vitamins

A standard daily multivitamin is a reasonable safety net while eating less. Anything beyond that is worth discussing with a pharmacist.

Support when you need it

Our team is available Monday to Friday by email at support@everydaymeds.co.uk, through the account portal chat, or on 0333 207 0413. Ongoing monthly reviews, dose titration and follow-up assessments are handled by the prescribing team, and repeat orders re-check suitability, with no auto-shipping.

10 · Is it right for you

Who GLP-1 treatment suits, and who it does not

GLP-1 treatment suits adults who meet the licensed criteria, who understand that diet and activity remain part of the plan, and who are ready for ongoing treatment. It does not suit everyone, and a prescriber has the final word.

Who it is designed for

Mounjaro is licensed for weight management in adults and for type 2 diabetes. It is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. A consultation is how suitability is judged, because your history, other medicines and goals all matter. Our customer journey is simple: a free online health questionnaire, a prescriber review, dispensing by our registered pharmacy, then free next-day tracked delivery.

Who should think twice

People who are not looking to treat a weight-related health problem, who want a quick cosmetic change, or who are unwilling to adjust their eating are unlikely to get what they hope for. The medicine is licensed alongside a reduced-calorie diet and increased physical activity, so it is not a stand-alone fix. If you take insulin, a sulfonylurea, warfarin or other narrow-margin medicines, your prescriber needs to know in detail.¹

Can a healthy person take it?

If you are already at a healthy weight, treatment is unlikely to be appropriate. Do not try to obtain a prescription medicine from a seller who skips the consultation.

Pros and cons compared with metformin

The responsible answer is that this is a question for your prescriber or pharmacist, who can weigh your own history. Do not start or stop either medicine based on a general web summary.

Which GLP medicine is right for me?

What matters is whether a particular medicine suits your health, your other treatment and your goals. A GPhC-registered prescriber can assess that. For the broader range of treatment options, see our weight loss clinic page. For Wegovy, the Wegovy pen page has current details.

Fat burning or appetite suppression?

Mounjaro helps you feel fuller sooner and less hungry between meals and slows how quickly the stomach empties, which supports a reduced-calorie diet. The weight lost comes from eating less, and some of any rapid loss can come from lean tissue, which is why protein and resistance exercise matter. We would not describe it as a fat-burning drug.

11 · Weighing your decision

How to weigh up the pros and cons for yourself

The most useful way to decide is to put your own priorities against the evidence, not to look for a universal yes or no. A pro that matters enormously to one person may count for little to another, and the same is true of cons.

Start with your goal

Ask what you are hoping the treatment will do. If you want a large reduction in weight to improve health, the trial averages are encouraging. In SURMOUNT-1, people on 15mg lost on average 20.9% of their body weight over 72 weeks, compared with 3.1% with lifestyle changes alone. As a worked example, for someone starting at 100 kg, 20.9% is about 21 kg. That is an average, not a forecast, and individual results vary.²

Be honest about the cons that would bother you

If you already have a sensitive stomach, if you struggle to drink enough, or if you eat irregularly, plan for how you would manage the digestive effects. If you cannot tolerate the idea of ongoing treatment, factor that in. If cost is the sticking point, compare the monthly outlay with what you can sustain, not just the first order.

Think about the long view

Treatment is a commitment that includes regular reviews, dose adjustments and habit changes. The weight is more likely to stay off if the habits that support it, including protein, movement and hydration, are in place before you stop. Exercise also protects against regain if you later stop treatment.

Ask the right questions

When you speak to a prescriber, it helps to ask about your current medicines, any condition that affects your digestion or kidneys, and how the dose will be stepped up. Ask what to do if side effects are hard to cope with, and what the plan is if you want to stop.

Use trusted sources

The patient information leaflet, the NHS pages on tirzepatide and the BNF are reliable places to confirm details.⁵ Be cautious about summaries that give very high success figures without naming the trial, the dose and the duration.

When to speak to someone

If you are unsure, the simplest next step is to complete the free consultation. There is no obligation, a GPhC-registered prescriber reviews it, and you can stop at any point before payment is taken.

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