Mounjaro Tirzepatide Injection Pen 5mg: Price, Dosing and Results (October 2026)

01 · Price and ordering

What a Mounjaro 5mg pen costs in the UK

The Mounjaro pen at 5mg has a standard price of £189.99 for one pen, which is £47.50 per week across the four doses inside. That is what a repeat order costs before any discount. A new customer's first order at any dose, including 5mg, is £40 less with code FIRST40. Every later order then gets an automatic £25 off the standard price (code DOSE25).

Across the UK pharmacies we track (checked 27 October 2026), Mounjaro pens range from £143.96 to £319.99 depending on dose and provider, and the gap between providers for the same dose runs from £20 to £36.03. Compare like for like: same dose, same genuine KwikPen, same clinical review.

The price shown is the price paid. The consultation is free, and there are no hidden fees. All six doses are in stock, and you can pay by Visa, Mastercard, Klarna or pay-monthly options, with no subscription.

02 · Planning

How 5mg fits into your first year

Nobody starts on 5mg. A first year of 52 weeks and 13 pens 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. These totals are before discounts: your first order is £40 less and every later order £25 less.

If you stay at 5mg, your ongoing monthly cost is the 5mg price less the £25 reorder discount. Our 2.5mg starter price guide shows the first step in detail.

03 · How to order

How to order the 5mg pen

Ordering takes three steps, and you can begin with our free online consultation.

• Free consultation: a short health questionnaire, with no charge and no obligation.
• Prescriber review: a GPhC-registered prescriber reviews your answers. 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: our registered pharmacy dispenses your pen. Same-day dispatch applies when you order by 3pm, with free next-day tracked delivery in temperature-controlled, discreet packaging. Saturday delivery is £14.99.

Needles, a sharps bin and injection guidance come with every order. Repeat orders re-check suitability and there is no auto-shipping, so you stay in control of each pen. Our prescribing team also provides monthly reviews and dose-titration support. Genuine KwikPens come direct from official LillyDirect supply, and we are GPhC-registered (9012878).

04 · What the 5mg pen is

What is a Mounjaro tirzepatide 5mg injection pen?

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

The 5mg pen delivers 5mg at each weekly injection, and each pen contains four weekly doses.¹³ Think of it as a one-month supply at one fixed dose. A single pen is a complete unit rather than a bulk vial, and you cannot draw up a different amount. Our single Mounjaro injection pen page covers how one pen is supplied.

05 · How 5mg works

How tirzepatide 5mg works in the body

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.¹ In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.

This dual action distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide (Wegovy/Ozempic). Our guide on how the Mounjaro injection pen works explains the device side as well.

Tirzepatide has a half-life of about five days. 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

06 · Weight loss on 5mg

Can you lose weight on 5mg Mounjaro?

Yes. 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 over 72 weeks, compared with 3.1% with lifestyle changes alone.² At 72 weeks, 85% of participants on 5mg had lost at least 5% of their body weight.²

As a worked example, for someone starting at 100 kg, 15% is about 15 kg. These are trial averages. Individual results vary, and the treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

For comparison, the same trial reported 19.5% on 10mg and 20.9% on 15mg over 72 weeks.² It does not mean everyone should aim for the top dose. Many people settle at a maintenance dose of 5mg, 10mg or 15mg, and higher is not automatically better.¹

Our weight loss injection pen overview sets Mounjaro in the wider context of injectable options.

07 · Pace of results

What pace to expect on 5mg

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.² The trials measured results at 72 weeks, so think in months, not days, and judge progress by trend rather than individual weigh-ins.

Experiences in the early weeks differ widely. Some people notice appetite change and early loss in week one. Others feel little until a higher dose. Both are normal. Early loss includes water weight, so the trend over weeks matters more than any single weigh-in.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 Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹³

If side effects feel troublesome, tell your prescriber.

08 · Titration and 5mg

How long you stay on 5mg and when to step up

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 four weeks the dose increases to 5mg. It can then step up by 2.5mg at a minimum of four-week intervals (7.5mg, 10mg, 12.5mg) up to a maximum of 15mg weekly, depending on how you respond and tolerate it.¹

So there is no fixed time on 5mg. Four weeks is the minimum before a step-up is possible, not a target. Many people settle at a maintenance dose of 5mg, 10mg or 15mg, and your prescriber guides the pace.¹

Is 7.5mg stronger than 5mg? Yes. 7.5mg is the next strength up, one 2.5mg step above 5mg. Whether to step up depends on how you respond and tolerate treatment, so the step is a decision with your prescriber.

Switching to us from another provider at a higher dose? Your first order at 15mg is £259.99, and your prescriber will review your dose first.

09 · Using the 5mg pen

How to use a Mounjaro 5mg pen

Mounjaro is injected under the skin once a week, on the same day each week, at any time of day, with or without food.¹³ Licensed sites are the stomach area (at least 5cm from the belly button), the front of the thigh, or the back of the upper arm if someone else gives the injection. Rotate the site with each dose.¹³

Follow the pen's instructions for the exact steps. Our walkthroughs on how to use a Mounjaro injection pen, Mounjaro injection technique and Mounjaro preparation cover the details, and the leaflet in your box is the final authority. If you are newer to injectables, the guide to using a weight loss injection pen is a gentle start.

Best time of day: there is no best time. Mounjaro works the same morning or evening, with or without food. What matters is the same day each week. Many people choose a weekend morning so early side effects fall on days off.¹³

Changing your injection day: you can do this as long as at least 3 days (72 hours) have passed since your last dose.¹³

10 · Clicks and doses

Clicks, doses and what is inside a 5mg pen

How many clicks are in a 5mg pen? You do not count clicks. The KwikPen is set by turning the dose knob until the dose indicator shows the correct dose in the window.

How many 2.5mg doses are in a 5mg pen? None. A 5mg pen is made to deliver 5mg at each of its four weekly doses. It is not designed to be used as a source of 2.5mg doses.

Can you use a pen after four doses? Each pen is made for four weekly doses. Once in use, a pen can be kept out of the fridge not above 30°C for up to 30 days, after which it should be discarded.¹³ Discard the pen after the fourth dose and start the next one.

11 · Storage and travel

Storing and travelling with your 5mg pen

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.¹³

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, and 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. Figures circulating online often come from other countries' labels.¹³

12 · Missed doses

What to do if you miss a 5mg dose

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.¹³

If you want to move your injection day for good, the same 3-day (72-hour) gap rule applies between two doses.¹³

13 · Eligibility and NHS

Who can be prescribed Mounjaro, and the NHS picture

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. A prescriber will assess your BMI, medical history and current medicines before deciding whether it is suitable for you.¹

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.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.

Browse all weight loss treatments if you want to compare options, or read our guide to tirzepatide injection online prescription in the UK.

14 · Buying safely

Buying a genuine 5mg pen safely

Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. Be wary of anyone offering to supply without a consultation or prescription, or selling pens through social media or marketplaces.

You can check any UK pharmacy on the GPhC register. Ours is registration 9012878 (GPhC register entry).¹² Our Mounjaro comes direct from Eli Lilly's UK distribution through official LillyDirect supply, as genuine KwikPens. For more, see tirzepatide injection single pen UK, or the Jupiter Mounjaro page if you have seen that name used.

Mounjaro is used alongside a reduced-calorie diet and increased physical activity. Individual results vary. This page is information, not a substitute for medical advice.

15 · 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