What Was the First Weight Loss Injection? (October 2026)

01 · The answer

So which injection came first, and does it matter to you?

The injection most often named as the first of the modern generation is liraglutide, sold for weight management as Saxenda. It is a GLP-1 medicine given once a day, and it is supplied at a concentration of 6mg per millilitre.

The messier answer is that 'first' depends on your definition. Liraglutide is the daily GLP-1 injection usually named as the forerunner of today's options. If you mean the first injection that acts on both GIP and GLP-1 receptors, that is tirzepatide, the active ingredient in Mounjaro.

For most readers the history is interesting but not the decision. The decision is which treatment suits you now. Daily liraglutide has been followed by weekly semaglutide (Wegovy) and weekly tirzepatide (Mounjaro). A weekly pen is simply easier to live with for many people.

02 · Your next step

What should you do with this information?

If you are curious only, you have your answer. If you are considering treatment, start with the licence. Mounjaro is licensed in the UK for weight management in adults and for type 2 diabetes, used alongside a reduced-calorie diet and increased physical activity. Individual results vary.

Three practical questions help most people decide. First, does a once-weekly routine suit your life better than a daily one? Second, do you meet the criteria for NHS care, or would you prefer regulated private treatment? Third, are you comfortable with the monthly review and dose-step process that goes with any of these medicines? A prescriber can talk each of these through with you.

If you want to see where the current medicine sits on cost, the Mounjaro pen, with prices and consultation is the place to look. Your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99), and every later order is £25 off the standard price. If you are comparing several options, our guide to weight loss injection choices sets them side by side, and the wider weight loss clinic explains how our service works.

03 · How it works

How ordering Mounjaro works with us

EverydayMeds is a GPhC-registered UK online pharmacy (registration GPhC 9012878). Mounjaro is supplied only after an online consultation that is reviewed by a GPhC-registered prescriber. The process is straightforward:

• Complete the free online consultation, a short health questionnaire with no charge and no 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 it, with same-day dispatch when ordered by 3pm, then free next-day tracked delivery in discreet, temperature-controlled packaging. Saturday delivery is £14.99.

All six strengths are in stock, and we supply genuine KwikPens through official LillyDirect supply, direct from Eli Lilly's UK distribution. Needles, a sharps bin and injection guidance come with every order. There are no subscriptions, and repeat orders re-check suitability rather than shipping automatically.

Related guides: Zenpep weight loss injection and Bonjour weight loss injection and Hypnotic weight loss injection.

04 · Daily to weekly

From a daily injection to a weekly pen

The biggest change between the first modern weight loss injection and today's options is how often you inject. Liraglutide, including Saxenda and products such as Erly, is a daily injection. It is supplied at a concentration of 6mg per millilitre. Wegovy and Mounjaro are different: both are given once a week.¹⁸

That shift matters more than it sounds. A daily medicine asks you to build the injection into every single day, including holidays, busy weeks and early mornings. A weekly medicine asks you to remember one day.

Wegovy (semaglutide) comes as pens in the strengths 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg once weekly. The dose steps up after at least four weeks, reaching the 2.4mg maintenance dose from week 17, and 2.4mg is the licensed maintenance dose for weight management.¹⁸

Mounjaro (tirzepatide) is the brand name for 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 Each KwikPen contains four weekly doses, so one pen covers a month of treatment.¹

It helps to think of these as generations rather than rivals. The weekly semaglutide pen made the routine easier. The weekly tirzepatide pen added a second hormone target. Each step kept the same basic idea: a regular injection under the skin, working alongside a reduced-calorie diet and increased physical activity.

One more point of honesty: being first does not make a medicine better or worse. The sensible questions for any treatment are whether it is licensed for your situation, what the trials show, what the side effects are and whether you can realistically stick to it.

05 · How the injections work

How weight loss injections actually work

Weight loss injections of this kind copy natural gut hormones that tell your body you have eaten. Liraglutide and semaglutide act on the GLP-1 pathway only. Tirzepatide goes a step further: it 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. This dual action is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide (Wegovy/Ozempic).

It is worth being clear about what that means. They change appetite signals and digestion speed, which makes it easier to eat less without constant hunger. The diet and activity changes still do the work, and the medicine makes them more achievable. That is why every licensed use sits alongside a reduced-calorie diet and increased physical activity.

Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects, and they usually settle. If something does not settle, or a new symptom worries you, tell your prescriber. You can also report suspected side effects through the MHRA Yellow Card scheme.¹⁹

Because the medicine stays in the body for some time, stopping is not instant either. 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.

The same slower stomach emptying has one practical consequence worth knowing. The medicine can reduce absorption of oral contraceptives because stomach emptying slows, so if you use one, raise it in your consultation and your prescriber can advise. 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 a sulfonylurea for diabetes, doses may need adjusting because of the risk of low blood sugar. This is a conversation to have with your prescriber before you start, not something to work out alone.

Understanding the mechanism also helps you see why there is no shortcut. Appetite medicines support a pattern of eating less over months. They do not replace it, and they are not a quick fix.

06 · What the evidence shows

What the trial evidence says about Mounjaro

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

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

A worked example makes the average easier to picture. For someone starting at 100 kg, 20.9% is about 21 kg. That is arithmetic on a trial average, not a forecast of what you will lose.

Results from separate trials, with different people, durations and doses, should not be set against each other as if they were head to head. The only clean way to compare tirzepatide with semaglutide is a trial that tested them directly, and SURMOUNT-5 is that trial.¹⁵ If someone tells you one medicine is simply better, ask which trial they mean.

The pace of results matters for expectations too. Weight loss on Mounjaro is gradual by design. The first weeks on 2.5mg are an adjustment phase and losses are usually modest; most measurable progress builds from 5mg onward, month by month. Trials measured results at 72 weeks, so think in months, not days, and judge progress by trend, not individual weigh-ins.¹

Treatment response is reviewed by your prescriber: 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

The early weeks are also less dramatic than people expect. Some people notice appetite change and early loss in week one, others feel little until a higher dose, and both are normal. Early loss includes water weight, so the trend over weeks matters more than any single weigh-in.

Neither fact tells you how you personally will respond, which is exactly why a prescriber reviews progress rather than leaving you to guess.

07 · Dosing and injecting

How a weekly pen is dosed and injected

Everyone starts Mounjaro on 2.5mg once a week. This starting dose is about letting your body adjust, not about weight loss itself. After at least 4 weeks the dose increases to 5mg, and can then step up by 2.5mg at a minimum of 4-week intervals up to a maximum of 15mg weekly, depending on how you respond and tolerate it. Many people settle at a maintenance dose of 5mg, 10mg or 15mg. Higher is not automatically better, and your prescriber will guide the right pace.¹

Mounjaro is injected under the skin (subcutaneously) once a week, on the same day each week, at any time of day, with or without food. Licensed injection sites are the stomach area, the front of the thigh, or the back of the upper arm if someone else gives the injection. Rotate the site with each dose. Each KwikPen contains four weekly doses.¹

There is no 'best' time of day. Mounjaro works the same morning or evening, with or without food. What matters is the same day each week. Pick a day and time you will remember. Many people choose a weekend morning so early side effects fall on days off, and then stick to it.

The pen is set by turning the dose knob until the dose indicator shows the correct dose in the window.

Missing a dose is common and has a clear rule. If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time, then carry on with your usual day. If more than 4 days have passed, skip the missed dose entirely and take the next one on your normal day — never take two doses within 3 days of each other.

You can change your weekly injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.

08 · Storage and travel

Storing and travelling with a weekly injection

Keep Mounjaro pens in a fridge at 2–8°C and never freeze them. Once in use, a pen can be kept out of the fridge not above 30°C for up to 30 days, which is useful for short trips, after which it should be discarded. Keep the pen cap on to protect it from light, and never use a pen that has been frozen.¹

A pen in use covers a month of weekly doses, and it can be kept out of the fridge at a temperature not above 30°C for up to 30 days after first use. Most holidays therefore need no special arrangements.

You can fly with Mounjaro. Carry pens in hand luggage, because hold luggage can fall below freezing, ideally in a cool bag with the prescription label or a copy of your prescription. For hot climates use an insulated pouch, which is a small accessory purchase. Check destination rules for travelling with prescription injectables before you fly.¹³

Unopened pens should be kept in the fridge and keep until the expiry date printed on the box. If an unopened pen has been out of the fridge, check with the pharmacy before using it rather than relying on a remembered day limit.

Deliveries from us arrive in discreet, temperature-controlled packaging by free next-day tracked delivery. When your parcel arrives, put the pens in the fridge unless one is about to be used. If something looks wrong, such as a damaged pen or wrong item, contact us within the window set out in our refund terms; dispensed prescription medicines cannot otherwise be returned.

A few habits make storage painless. Keep your spare pens together on a fridge shelf, away from the freezer compartment and the back wall where items can freeze. Leave the cap on between uses. Use your own label or note to track which pen is in use and when you opened it, so you know when the in-use period ends and the pen should be discarded.

If you ever doubt whether a pen is safe to use, do not inject it. Ask the pharmacy. Sterility and potency are no longer assured once a pen is outside the tested window, and a replacement is a better outcome than a risky dose.

The same careful approach applies to where you buy. Counterfeit weight loss injections are a real problem, and the MHRA publishes alerts about them. Buy only from a registered pharmacy that supplies after a consultation. You can check ours on the GPhC register (registration 9012878).⁷

09 · NHS and private care

NHS or private: how people get these injections now

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. 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

Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting. Whether you go via the NHS or privately, the medicine is the same, and so is the principle that treatment sits alongside a reduced-calorie diet and increased physical activity.

NHS access to Wegovy runs through specialist weight-management services, so ask your GP about it.

If you go privately, the practical points are cost, speed and support. With us, the consultation is free, the price shown is the price paid, and there are no hidden fees. Standard monthly prices depend on the dose: the 2.5mg pen is £169.99, the 5mg pen is £218.99 and the 15mg pen is £329.99. A new customer's first order is £40 less with code FIRST40, and every later order is £25 less than the standard price.

For planning ahead, 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, again before discounts. For other maintenance doses, use the monthly price: £279.99 at 7.5mg, £290.99 at 10mg and £319.99 at 12.5mg. Across the UK pharmacies we track, Mounjaro pens ranged from £143.96 to £339.00 as of 11 October 2026, and the gap between providers for the same dose ranged from £27 to £41.

Payment options include Visa and Mastercard, Klarna and pay-monthly options, with no subscriptions. Aftercare includes ongoing monthly reviews, dose-titration and follow-up assessments by the prescribing team, and side-effect support. You can reach support Monday to Friday, 9am to 5pm, by email at support@everydaymeds.co.uk, through the account portal chat or by phone on 0333 207 0413.

The honest summary is that neither route is universally better. The NHS route costs nothing at the point of use but is limited by criteria and local capacity. The private route is available to adults who the prescriber judges suitable, at a cost. Many people simply want to know which route their circumstances fit, and a free consultation is a low-pressure way to find out. If you want to see what stock looks like across the wider market, our page on the weight loss injection in stock in the UK covers it.

10 · Claims to treat with caution

Nicknames, celebrity stories and 'natural' alternatives

First, nicknames such as 'nature's Ozempic' or the 'poor man's Ozempic' are marketing phrases, not medical categories. They usually describe low-cost supplements with no clinical oversight. Dosing is not standardised, and they have nothing like the licensing, trial evidence or prescriber review of licensed weight loss injections.

Dramatic weight-loss claims attached to them should be treated with scepticism.

Second, stories about famous people taking one medicine or another are not evidence. They also tell you nothing about whether a medicine is right for you. The meaningful questions are the ones a prescriber asks in a consultation: your health history, your other medicines and your goals.

Third, be wary of anyone offering to supply a prescription injection without a consultation or prescription. Genuine supply of Mounjaro requires a prescription-only process reviewed by a GPhC-registered prescriber. Sellers that skip it may be selling counterfeit or unsafe products. The MHRA publishes counterfeit medicine alerts and runs the Yellow Card scheme for reporting suspected problems.⁷

Fourth, beware of confident statements about newer products that claim to be 'better than Mounjaro'. Tablet versions of GLP-1 medicines also exist, including Wegovy tablets and Foundayo. Their results should not be set against Mounjaro's as if head to head.

Finally, remember this is information, not a substitute for medical advice. Mounjaro (tirzepatide) is a prescription-only medicine supplied only after an online consultation reviewed by a GPhC-registered prescriber, and individual results vary.

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 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.