Full Mounjaro Pen: What a Full KwikPen Contains (October 2026)

01 · The core answer

What a full Mounjaro pen contains

A full Mounjaro pen is a pre-filled KwikPen holding the weekly doses for one month at one strength. Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine made by Eli Lilly. 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.¹¹³ That is why we describe one pen as one month of treatment. You do not draw up the medicine yourself and you do not measure anything. The pen does the metering, and you simply dial to the strength you were prescribed.

If you are weighing up cost, our guide to the full price of Mounjaro explains how list and pharmacy prices differ. Your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99). Every later order is £25 off the standard price, using code DOSE25.

02 · Checking your pen

How to tell whether your pen is still full

The dial window tells you whether a pen still has a full dose left. You turn the dose knob until the dose indicator shows the correct dose in the window.

Do not top up with a second pen or try to combine leftovers. Start a fresh pen on your next injection day.

If you are ready to start or restart treatment, the Mounjaro pen page has live prices for every strength and the free online consultation.

03 · Doses and strengths

One pen, one strength, weekly doses

A pen holds one strength only, so the number on the box is the dose you inject every week of that pen. 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. Each KwikPen contains four weekly doses.¹¹³

People often ask whether a multi-dose pen is really meant to be used across several injections. It is, and our short explainer on whether Mounjaro is a multidose pen covers the design in more detail. The pen is built so that each dial setting delivers the same prescribed amount, week after week, until it is used up.

Treatment follows a set ladder. Everyone starts Mounjaro on 2.5mg once a week. This starting dose is about letting your body adjust, not about weight loss itself.¹ Your prescriber decides when to move up, and each step up means opening a pen of the next strength.

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 Because each strength is its own pen, you will usually finish a pen before changing dose rather than switching halfway through.

04 · Using the dial

Setting the dose and injecting

Setting the dose is a matter of reading the window, not listening for sounds.

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.¹¹³ Rotating helps avoid irritation in one spot.

For the full routine, including attaching a fresh needle and following the instructions that come with the pen, see our guide to preparing your pen. Needles, a sharps bin and injection guidance are included with every order, so you do not need to buy anything separately to start.

Follow the pen's own instructions for the injection itself, including how long to hold it in place. Those steps are written for this exact device, and a general guess is no substitute.

05 · Storing a full pen

Storing a full pen safely

Unopened pens belong in the fridge until you start them. Keep Mounjaro pens in a fridge at 2–8°C and never freeze them.¹¹³ Unopened pens should be kept in the fridge and keep until the expiry date printed on the box.¹

Once you start a pen, the rules relax slightly. Once in use, a pen can be kept out of the fridge not above 30°C for up to 30 days — useful for short trips — after which it should be discarded.¹ Keep the pen cap on to protect it from light, and never use a pen that has been frozen.¹

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.¹ We would rather answer that question than have you guess.

Travelling with a pen is straightforward. You can fly with Mounjaro. Carry pens in hand luggage (hold luggage can fall below freezing), ideally in a cool bag with the prescription label or a copy of your prescription.¹ For hot climates, an insulated pouch is sensible, and you should check destination rules for prescription injectables before you fly.

06 · Timing and missed doses

Timing doses from a pen

The day matters more than the hour. There is no “best” time of day — Mounjaro works the same morning or evening, with or without food.¹ What matters is the same day each week. Many people choose a weekend morning so early side effects fall on days off.

If you miss a dose, the rule is clear. 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.¹¹³ 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.¹

A missed dose does not change how the pen works; you simply carry on from the medicine that remains. Changing your day is also allowed. You can change your weekly injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.¹

07 · Finishing a pen

Finishing a pen, and why not to stretch it

A pen is finished when it has delivered its weekly doses and the window will no longer turn to a full dose. Our page on what to do with a finished pen covers safe disposal using the sharps bin supplied.

It can be tempting to squeeze extra value from a nearly empty pen, or to take smaller doses so a pen lasts longer. We do not support that.

Altering doses outside the licence means unknown dosing accuracy and no safety data.¹ If cost is the worry, talk to your clinical team rather than self-adjusting.

Pens are prescribed to an individual after a consultation, so they should not be passed between people. Our guide to sharing a pen explains why.

Stopping treatment is a separate matter from finishing a pen. 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

08 · When “full” means feeling full

If you mean feeling full on Mounjaro

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.¹ That is the medicine working as intended. If the fullness is uncomfortable, our pages on feeling full on Mounjaro and feeling too full explain what is expected and what to raise with your prescriber.

Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹ Report anything new or worrying to your prescriber, and you can also report side effects through the MHRA Yellow Card scheme. 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 the skin or eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing.

09 · What to expect from treatment

What to expect from your first pens

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.¹ Trials measured results at 72 weeks — think in months, not days, and judge progress by trend, not individual weigh-ins.¹

So the answer to how much you can lose in the first few months is that it varies, and early results are usually modest. 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

For context on longer-term results: 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.²

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

10 · Cost, NHS and ordering

Cost, NHS access and how ordering works

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.

Across the UK pharmacies we track, Mounjaro pens range from £143.96 to £339.00 per month depending on dose and provider (checked 10 October 2026). The gap between providers for the same dose can be as small as £27 or as large as £41, so comparing is worthwhile.

Ordering with us follows a short path:

• 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 your pen, with same-day dispatch when ordered by 3pm, and free next-day tracked delivery in temperature-controlled packaging.

All six strengths are in stock, supplied through official LillyDirect supply direct from Eli Lilly's UK distribution. Browse live prices on the Mounjaro pen page, or see our weight loss clinic for the wider service.