Mounjaro Injection Pen: How It Works, How Many Doses and How to Use It (October 2026)

01 · The core answer

How many injections are in a Mounjaro pen?

Each Mounjaro KwikPen contains four weekly doses.¹ One pen is four weeks of treatment at a given strength, and the pen is designed so that you use all four doses and then discard it.

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

The strength printed on the pen is the dose you inject each week. It is not the total in the pen.

02 · Dial and clicks

Clicks, the dose window and what to do if it will not turn

You do not count clicks on a Mounjaro KwikPen. You set the dose by turning the dose knob until the dose indicator shows the correct dose in the window, and you confirm it by the number in the window.

Do not use part of a stronger pen to make up a lower dose. If you need a different strength, your prescriber can arrange the right pen rather than you adjusting a pen you already hold.¹

03 · What to do next

Is this relevant to you, and what to do next

If you already have a prescription, follow the dose, storage and missed-dose guidance for your pen.

If you are still deciding whether to start, Mounjaro is a prescription-only medicine supplied only after an online consultation reviewed by a GPhC-registered prescriber. You can read more on our weight loss clinic page. When you are ready to check strengths and costs, the Mounjaro pen prices and consultation page shows live prices. Every strength is in stock, and the free consultation comes with no obligation.

04 · What is in the pen

What is inside a Mounjaro KwikPen

A Mounjaro KwikPen is a pre-filled, disposable pen containing tirzepatide solution. You do not draw medicine from a vial, and you do not refill the pen. A new needle is attached for each injection, and our orders include needles, a sharps bin and injection guidance.

The pen is supplied in six strengths, each one a fixed weekly dose. Each pen contains four weekly doses. That is why a prescriber speaks of a pen as a month of treatment, though strictly it is four weekly injections. If you are curious about whether pens can be topped up, our page on refillable GLP-1 pens explains the difference between refillable and pre-filled devices.

The medicine is the same whatever the strength. What changes is the amount per weekly dose. Because the strength is printed on the pen, always check the label against your prescriber's current instructions before you inject. If you are unsure, contact the pharmacy rather than guessing.

A pen is a prescription-only medicine, so it should only reach you through a regulated pharmacy after a consultation. Our official LillyDirect supply means genuine KwikPens sourced directly from Eli Lilly's UK distribution.

05 · How the medicine works

How the tirzepatide in the pen works

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 is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide (Wegovy/Ozempic). For a plain-English walkthrough, see how the pen's medicine works. If you are comparing devices, our overview of other weight loss injection pens sets them side by side.

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.¹

06 · Doses and titration

Which pen strength do you start on?

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 (7.5mg, 10mg, 12.5mg) up to a maximum of 15mg weekly, depending on how you respond and tolerate it.¹

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.¹¹ Because each pen holds four weekly doses, you move to a new pen when your prescriber moves you to a new strength, or when the current pen is finished.

If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £879.96 at standard prices. A new customer's first order is £40 less, and every later order is £25 less.

If you want to see what one of the mid-range pens looks like in practice, our 5mg single pen page covers that strength.

07 · Can 2.5mg work?

Can you lose weight on the 2.5mg pen?

The 2.5mg pen is a starting dose, and its purpose is adjustment rather than weight loss itself.¹ The 2.5mg starting weeks are about adjustment, and experiences 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. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.

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.

08 · Trial results

What the trial showed for the strengths in the pens

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. 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

As a worked example, for someone starting at 100 kg, 20.9% is about 21 kg. Trial averages do not predict your own result, and your prescriber reviews your response. 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

09 · Injecting weekly

When and where to inject

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.¹³ Licensed injection 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.

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.

Follow the instructions supplied with the pen for the exact injection steps. For the full routine, use our step-by-step injection guide alongside the patient leaflet.

10 · Missed doses and day changes

Missed doses and changing your injection day

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

You can change your weekly injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.¹³

These rules work within the pen's design: each pen contains four weekly doses, so skipping a dose does not give you a spare one to use later. Ask your prescriber if you are unsure.

11 · Storage and travel

Storing the pen and travelling with it

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 at a temperature not above 30°C for up to 30 days after first use, useful for short trips, and must then be thrown away. Do not use a pen that has been above 30°C. Keep the pen cap on to protect it from light, and never use a pen that has been frozen.¹

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. In-use pens tolerate up to 30 days not above 30°C, so most holidays need no special arrangements. For hot climates use an insulated pouch. Check destination rules for travelling with prescription injectables before you fly.¹

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.

If a pen is cracked, leaking or will not dial, read our page on a damaged or broken pen and contact the pharmacy.

12 · Getting a genuine pen

Getting a genuine pen safely

Mounjaro is a prescription-only medicine, so any seller offering to supply without a consultation or prescription is a warning sign. The MHRA publishes counterfeit medicine alerts and runs the Yellow Card scheme for reporting suspected fake products and side effects.⁷

EverydayMeds is a GPhC-registered UK online pharmacy (registration 9012878), and you can check it on the GPhC register.¹² Our Mounjaro comes through official LillyDirect supply, direct from Eli Lilly's UK distribution, and is delivered free next day in temperature-controlled packaging. Same-day dispatch applies when you order by 3pm.

13 · Cost and NHS access

What a Mounjaro pen costs and the NHS route

The standard price of a 2.5mg pen is £169.99 per month, and every later order is £25 off the standard price (code DOSE25). Across the UK pharmacies we track, the cheapest and dearest Mounjaro pens were £143.96 to £319.99 when checked 25 October 2026.

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.⁴⁶

Our consultation is free, and the price shown is the price paid. Payment options include Visa, Mastercard and Klarna, with no subscriptions. Mounjaro is used alongside a reduced-calorie diet and increased physical activity, and individual results vary. 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.