GLP-1 Downsides: What to Weigh Up Before You Start (October 2026)

01 · The short version

What are the downsides of GLP-1 drugs?

The downsides of GLP-1 drugs fall into a few groups: side effects, practical burden, cost, access and expectations. None is hidden, and most can be discussed with a prescriber before you begin. If you want the detail for one specific medicine, our guide to the downsides of Mounjaro goes deeper.

Side effects come first. Every licensed GLP-1 or GIP/GLP-1 medicine has a patient information leaflet listing its possible effects.¹³ Most are digestive: for Mounjaro, nausea, diarrhoea, vomiting, constipation and abdominal discomfort affect more than 1 in 10 people, and they are most likely when starting or increasing a dose. Read the whole leaflet before you start, and ask the prescriber about anything that worries you. 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.

Next is the practical burden. Mounjaro is a once-weekly injectable medicine supplied as a pre-filled pen.¹ That suits many people. Others dislike needles or find a weekly routine a nuisance. Liraglutide is a daily injection, which is a heavier routine again.

Then there is cost. A private prescription is a recurring monthly expense for as long as you stay on treatment. Our Mounjaro pen starts at £169.99 for the 2.5mg starter pen at the standard price, and the price rises with dose. A new customer's first order is £40 less with code FIRST40, and every later order is £25 less. Prices were checked 10 October 2026. Over a year this is a real commitment, so plan for it before you start rather than after.

Access matters too. The NHS offers Mounjaro, but access is phased in over several years, starting with the highest-need groups.⁴ Many people who meet the licensed criteria therefore look at regulated private treatment instead, and that has a cost of its own.

02 · Your decision

Is taking a GLP-1 worth the risk?

Whether it is worth it depends on your health, your goals and your tolerance for the downsides, and a prescriber can help you weigh that up. The benefit side is documented. In the SURMOUNT-1 trial, 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.² These are trial averages, so individual results vary.

The question to ask yourself is not whether the medicine is risk-free. No medicine is. Ask whether your reasons for treatment are strong enough to justify the side effects, the injections and the cost. For some people with weight-related health conditions the answer is clearly yes.

If you are unsure, a free consultation with us costs nothing and carries no obligation. It is reviewed by a GPhC-registered prescriber, and if treatment is unsuitable your order is refunded automatically. You can start from our weight loss clinic page, and our guide explaining what GLP-1 is covers the basics if you are new to this.

03 · Next step

What to do with this information

Read the leaflet, think about the monthly cost, decide whether a weekly injection fits your life, and list every medicine you take. Then speak to a prescriber. If you decide to go ahead, our team provides ongoing monthly reviews, dose-titration support and side-effect support. Repeat orders re-check suitability, and nothing ships automatically, so you stay in control of whether you continue.

Finally, remember that deciding not to start is a legitimate outcome. A good consultation can end with the advice that treatment is not right for you right now. We would rather you hear that than start something you will stop soon after.

Related guides: Agonisti glp 1 and Trapezoid glp 1.

04 · Side effects

Side effects: the downside most people ask about

Side effects are the downside people raise most often: they are real, and they differ between people.¹³

Tirzepatide activates the GIP and GLP-1 receptors, which help regulate appetite and slow how quickly the stomach empties.¹ Most people feel fuller sooner and less hungry between meals. That is the intended effect, and it is also why eating habits often need to change. Talk through with your prescriber how your meals may feel different once treatment begins.

Effects tend to be discussed around dose changes, which is one reason treatment starts at a low strength and steps up. Our Mounjaro starter pen is 2.5mg, and the strengths run through 5mg, 7.5mg, 10mg, 12.5mg and 15mg. If a dose is not suiting you, say so at your monthly review rather than quietly putting up with it.

Do not rely on forums, social media or individual accounts to decide whether a symptom is related to the medicine. Online accounts are not evidence, and they can frighten people unnecessarily or reassure them wrongly. If you notice a new symptom, contact your prescriber or pharmacist and describe what is happening.

You can also report a suspected side effect yourself through the MHRA Yellow Card scheme, which helps regulators monitor medicines after they reach the public.¹⁹ You do not need to be certain the medicine caused it. Reporting is how safety signals are spotted.

A change in body odour is not listed as a side effect in the UK patient leaflet. Skin effects are listed: allergic reactions such as rash, itching or eczema are common, and a change in skin sensation is uncommon. Either way, tell your prescriber about any new or lasting symptom so they can look for other causes.

Our aftercare includes side-effect support as part of ongoing monthly reviews, so you are not left to manage this alone.

05 · Cost and commitment

Cost: an ongoing commitment, not a one-off

Cost is a genuine downside because private treatment is paid for month after month while you continue. It is worth stating this clearly, because the starting price can make the whole course look cheaper than it is.

Treatment begins with the 2.5mg starter pen, which costs £169.99 at the standard price. Strengths then step up, and higher doses cost more. At the other end, the 15mg pen costs £329.99 at the standard price. The monthly figures for the middle strengths are £218.99 for 5mg, £279.99 for 7.5mg, £290.99 for 10mg and £319.99 for 12.5mg. Every pen lasts four weeks.

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 settle at 5mg, up to £3,599.88 at 15mg. These totals are before discounts. A new customer's first order is £40 less with code FIRST40, and an automatic £25 reorder discount applies to every future order (code DOSE25).

Across the UK pharmacies we track, Mounjaro pens ranged from £143.96 to £339.00 per month across all doses when we checked on 10 October 2026. That spread is why it pays to compare, and why the consultation being free matters: you can see what is offered without paying anything.

The price shown is the price paid, with no hidden fees. We accept Visa and Mastercard, Klarna and pay-monthly options, and there are no subscriptions, so you can stop ordering whenever you decide to. Delivery is free next-day tracked, and Saturday delivery is £14.99.

There are costs beyond the pen too, though ours are included: needles, a sharps bin and injection guidance come with every order. What you cannot buy back is time spent on a treatment that does not suit you, which is why the consultation and the first few months of reviews matter.

A final honest point on cost. If your budget only stretches to a short course, think about what happens afterwards before you begin. Treatment works alongside a reduced-calorie diet and increased physical activity, and building those habits during treatment is what you will carry forward.² You can see the live pricing on our Mounjaro pen page.

06 · Stopping treatment

Stopping treatment: what to expect and what to ask

Stopping is a downside to think about in advance, because these medicines work while they are in your system and the effect depends on continuing. 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.¹⁴ Stopping should always be planned with your prescriber, with diet and activity habits ready to carry the load. Tirzepatide has a half-life of about five days, so after a final dose it takes roughly 4–5 weeks to clear the system.¹ There is no way to speed this up, and nothing needs doing while it clears.

That clearance time cuts both ways. If you stop because of a side effect, it will not vanish the next day, so contact your prescriber instead of waiting it out. If you stop for cost or convenience, remember the medicine's effect fades gradually rather than switching off overnight.

Why do people stop? The reasons are usually practical and personal: cost, the weekly routine, how they feel on a particular dose, a change in circumstances, or having reached their goal.

Before you start, ask the prescriber what the plan is for the end of treatment. Good questions include how dose reductions would work, what to do with diet and activity afterwards, and how to review progress once you are off the medicine. Having those answers up front is much better than improvising later.

The trial evidence reminds us that these results come from treatment alongside lifestyle change. In SURMOUNT-1, the comparison group made lifestyle changes alone and lost far less on average.² Lifestyle change is therefore not an optional extra. It is the part of the plan that stays with you if you stop.

If money is the pressure, tell your prescriber.

Finally, keep in mind that repeat orders with us re-check suitability and never auto-ship. You decide each month whether to continue, and you can stop ordering at any point.

07 · Results vary

Results vary: the downside of expectations

One of the quieter downsides is disappointment, because trial averages describe groups, not individuals, and your own result may be better or worse. Treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them, and individual results vary.²

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.² At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight.² Those are impressive averages, and they are also averages. Trial averages do not predict your own result.

Here is a worked example of what a percentage means. For someone starting at 100 kg, 20.9% is about 21 kg. That is a trial average on the 15mg dose over 72 weeks, not a target or a promise.

Mounjaro is not the only medicine with trial data. SURMOUNT-5 is the first large head-to-head trial of tirzepatide and semaglutide for weight loss.¹⁵ If you are choosing between medicines, your prescriber can explain how they compare for you.

Why might your result differ from the average? Dose reached, how consistently you take the medicine, diet, activity, other health conditions and other medicines can all play a role. Your prescriber will review your progress and talk through what is realistic.

It is also worth deciding in advance what success means beyond the scale. Many people value improvements in energy, mobility or blood test results as much as the number. Your prescriber can help you set goals that are about health, which tend to survive a slow month better than goals about a single figure.

08 · Who should be cautious

Who should not use GLP-1 medicines, or should take extra care

Mounjaro is not suitable for everyone. You should not take it if you are allergic to tirzepatide or any of its ingredients, and it should not be used during pregnancy or while 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. Always share your full medical history and medicine list during consultation.¹¹³

In the UK, Mounjaro is licensed for weight management in adults and for type 2 diabetes.¹ It is a prescription-only medicine supplied after an online consultation reviewed by a GPhC-registered prescriber, and used alongside a reduced-calorie diet and increased physical activity.

NICE recommends Mounjaro on the NHS for adults with a BMI of at least 35 plus at least one weight-related condition.⁴ Private supply follows the licence and prescriber judgement, which is why a consultation asks about your height, weight, history and medicines. Give accurate answers. A consultation is only as good as the information in it.

Tell the prescriber about every medicine you take, including those you buy over the counter, and about any health condition, past or present. Some medicines may need adjusting when you start. If you use insulin or sulfonylureas, the doses may need adjusting because of the risk of low blood sugar. Never change a prescribed dose on your own, and follow your prescriber's advice.

Say too if you are pregnant, planning a pregnancy or breastfeeding. 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. Current prescribing information indicates minimal transfer of tirzepatide into breast milk; discuss breastfeeding with your prescriber so the decision reflects your circumstances. Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed. 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.⁷

Mood is another subject people ask about. The EMA's safety committee reviewed the evidence and concluded in 2024 that it does not support a causal link between GLP-1 medicines and suicidal thoughts, and the MHRA keeps this under continuous review.¹⁷ Any big change in weight, appetite and routine can affect how you feel, so seek help promptly if your mood drops or you have distressing thoughts during treatment. It is also a reason to be open with your prescriber about your mental health history.

If you have thoughts of harming yourself or ending your life, get help straight away. Call 999 or go to A&E if you are in immediate danger. In England you can call NHS 111 and choose the mental health option, any time. You can also call Samaritans free on 116 123, day or night. Tell your prescriber about any change in your mood while taking Mounjaro.

09 · NHS and private access

Access: NHS versus private

Access is a downside because the NHS route exists but is phased, and the private route costs money. 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. For many that is a sensible choice. For others it is not affordable, and that is a real inequity worth naming.

If you think you may qualify for NHS treatment, ask your GP about it first. The NHS offers a route that does not depend on your budget, and it often comes with structured support. If you do not qualify yet or cannot wait, a regulated online pharmacy is the alternative. Check that it is registered with the GPhC. Ours is registration 9012878, and you can verify it on the public register.¹²

For Wegovy, NHS access runs through specialist weight-management services, so ask your GP. If you are comparing medicines, you can see our Wegovy pen alongside Mounjaro, and check availability at the time of order.

What does private supply give you? Our supply is official LillyDirect supply, meaning Mounjaro direct from Eli Lilly's UK distribution, with genuine KwikPens and all six doses stocked. All six doses are in stock. Orders placed by 3pm are dispatched the same day, and delivery is free next-day tracked in temperature-controlled packaging.

What does it not give you? It does not give you an NHS pathway, and it does not remove the cost. Be honest with yourself about whether you could sustain the monthly spend, and consider NHS routes in parallel if you might qualify.

Price changes are another reason to plan. Pharmacy sell prices vary because of confidential discounts, so compare current prices rather than relying on old figures.

10 · Supplements and alternatives

Poor man's Ozempic and natural alternatives

Products marketed as a natural or budget version of GLP-1 medicines are not equivalent to them, and relying on them is itself a downside. Terms like "nature's Ozempic" or "poor man's Ozempic" are marketing phrases, not clinical categories.

Berberine is the supplement most often given those labels. It is a low-cost supplement with no clinical oversight, and its dosing is not standardised.

Other products, such as fibre supplements or over-the-counter options, are available cheaply without assessment. Cheapness is the attraction and also the catch. Nobody reviews whether the product is suitable for you, whether it interacts with your medicines or whether you should be using it at all.

The licensed medicines do have approved trial results. For example, SURMOUNT-1 reported tirzepatide results over 72 weeks alongside diet and exercise.² Supplements marketed alongside them rarely come with comparable evidence. Our page about AMPK and GLP-1 explains why one pathway being linked to a supplement does not make the supplement a substitute.

Counterfeit and illegitimate sellers are a related danger. The MHRA publishes counterfeit medicine alerts and runs the Yellow Card scheme.⁷ Be wary of anyone offering to supply a prescription medicine without a consultation or prescription, whether through social media, beauty salons or unfamiliar websites. A very low price can be a warning sign in itself.

Check any pharmacy on the GPhC register before you buy.¹² Look for a named pharmacy, a registration number you can verify and a proper clinical review before supply. Ours is GPhC 9012878, and Mounjaro comes through official LillyDirect supply.

Spending money on a product that does nothing is a poorer outcome than saving for a licensed one.

11 · What I wish I knew

What to know before you start

The most useful thing to know before starting is that the medicine is a tool, and the plan around it decides how well it works. These are the points we would want any new patient to understand.

First, read the leaflet. It lists the possible effects and the situations in which care is needed, and it is written for you.¹³ Second, expect to change how you eat. Because the medicine slows stomach emptying and helps you feel fuller sooner, large meals may no longer feel comfortable.¹ Talk to your prescriber about meal size and composition, and use the weeks at a low dose to build habits.

Third, start low and do not rush. Mounjaro begins at 2.5mg and moves through the strengths only as your prescriber decides. There is no prize for reaching 15mg quickly, and a lower dose that works for you is a perfectly good outcome.

Fourth, do not expect the scale to be the only signal. Weight can move unevenly from week to week. Treatment works alongside a reduced-calorie diet and increased physical activity, so tracking meals, steps and how you feel gives a fuller picture.² Our free GLPTrackr companion app, on iOS and Android, is built for tracking a GLP-1 journey.

Fifth, know what not to do. Do not change doses on your own, do not take extra doses, do not use leftover pens from other people, and do not buy from sellers who skip the consultation. 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 the missed dose and take the next one on your normal day — never take two doses within 3 days of each other.

Sixth, keep pens stored as directed. They stay in the fridge at 2–8°C and must never be frozen; once in use, a KwikPen can be kept out of the fridge at a temperature not above 30°C for up to 30 days, and must then be thrown away. Do not use a pen that has been above 30°C or frozen. Follow the pen's instructions for injecting. If you are unsure about a pen that has been out of the fridge, check the patient information leaflet or ask the pharmacy rather than guessing.

Seventh, use your support. Our team is available Monday to Friday, 9am to 5pm, by email at support@everydaymeds.co.uk, through account portal chat, or on 0333 207 0413. Ongoing monthly reviews and follow-up assessments are part of the service.

Eighth, remember that the company behind a medicine matters less than how it is prescribed. Other manufacturers are active in this field, and our page on Boehringer Ingelheim and GLP-1 shows how the wider pipeline looks. Choose a licensed medicine supplied by a registered pharmacy, and you have covered the most important risk in the process.

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