Mounjaro Doses Per Pen: What a UK KwikPen Contains (October 2026)

01 · The core answer

How many doses are in a Mounjaro pen?

A Mounjaro KwikPen holds four weekly doses. Each KwikPen contains four weekly doses, and you inject on the same day each week, so one pen covers a month of treatment.¹ This is the same for every strength: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹³

The ladder itself comes from the licence. Everyone starts on 2.5mg once a week. 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.¹ Many people settle at a maintenance dose of 5mg, 10mg or 15mg, and higher is not automatically better.¹¹

02 · Your next step

What this means for you

If you are new to treatment, expect your first pen to be 2.5mg. That pen is about letting your body adjust, not about weight loss itself.¹ If you are switching from another provider at a higher dose, the pen still holds the same number of weekly doses; only the strength differs.

You can read the strength-specific guides for the 5mg pen, the 10mg pen and the 15mg pen.

When you are ready to start or reorder, you can see current strengths and complete the free consultation on the Mounjaro pen page. All six doses are in stock, and every pen is reviewed by a GPhC-registered prescriber before supply. Cost is covered in our guide to Mounjaro price per pen.

03 · How the dial works

How the KwikPen dial and dose window work

You set the dose by turning the dose knob until the indicator shows the correct dose in the window. You confirm the dose by the number in the window, never by counting clicks.¹³

The pen is also designed to protect you from mistakes near the end of its life. Each pen contains four weekly doses; the pen will not let you dial past the medicine left inside.¹³ That safeguard is part of the device, so you do not need to estimate how much is left by eye.

Our guide to Mounjaro clicks per pen and the explainer on how the pen works cover more of the injection routine.

Always follow the instructions that come with your pen, and use the patient information leaflet as your reference for the device steps.

04 · Leftover liquid at the end

What if there is liquid left after the final dose?

Treat the pen as finished once you have used its four weekly doses. You may notice some liquid still visible after the final injection, but that is not a spare dose you are entitled to use.

The reason is built into the design. If the window will not turn to a full dose, the pen does not contain enough for one and should not be used for a partial injection.¹³ Trying to combine leftovers, or to squeeze out an extra injection, would mean an unknown amount of medicine and no safety data behind it.

Taking smaller or more spread-out doses than the pen is designed to deliver is not licensed, not supported by the pen's design and not endorsed by any UK regulator.¹ If side effects are what is pushing you to stretch, speak to your prescriber instead. The licensed ladder already starts low for tolerability, and your prescriber can hold a dose longer or step down within the licence.

When the pen is finished, dispose of it safely. A sharps bin and injection guidance are included with every order.

05 · Storage and pen life

Storing a pen: fridge, in-use life and trips

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, after which it should be discarded.¹ Because a pen holds four weekly doses, a pen used on schedule is normally finished within that in-use window.

Keep the pen cap on to protect it from light, and never use a pen that has been frozen.¹³ Unopened pens should stay 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.

Your order arrives in temperature-controlled packaging by free next-day tracked delivery, with same-day dispatch when ordered by 3pm. Put the pens in the fridge as soon as they arrive.

06 · Travelling with pens

Travelling with a pen

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.¹³

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.

Because each pen is a month of weekly doses, planning is straightforward: count your injection days across the trip and carry the pens that cover them, with a little margin for delays. Your prescriber can advise on supply if you will be away across a reorder date.

07 · Injection day and missed doses

Missed doses and changing your injection day

Mounjaro is injected under the skin once a week, on the same day each week, at any time of day, with or without food.¹ There is no best time of day: it works the same in the morning or evening. Many people choose a weekend morning so early side effects fall on days off.

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

This matters for pen counting. A skipped dose is simply skipped; you do not make it up by injecting twice close together. If you are wondering about taking more than once in a week, see our guide to Mounjaro two doses per week.

08 · Injecting and sites

Where to inject from your pen

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.¹³

Rotating matters because each pen gives you four injections in a short window; using the same spot each time is the easy habit to fall into. Keep a simple note of where you injected last, or log it in the free GLPTrackr companion app.

Follow the pen's own instructions for each step of the injection.

09 · Pens across your treatment

How pens map onto titration and the long term

Titration is the stretch where you move up the ladder, with at least 4 weeks on each dose, depending on how you respond. 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).

Not everyone goes up every step. Your prescriber guides the pace and may hold a dose longer if side effects are the concern.⁴ Weight loss is gradual by design: the first weeks on 2.5mg are an adjustment phase and losses are usually modest, and most measurable progress builds from 5mg onward, month by month.⁴

For context on what the doses are working towards: 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, and individual results vary.

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. Nothing needs doing while it clears, and there is no way to speed it up.¹

10 · Getting pens

Getting your next pen

Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. Individual results vary.

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).⁴ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment.

Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. Repeat orders re-check suitability, and there is no auto-shipping. Our weight loss clinic page explains the wider service, and the UK-specific walkthrough in our UK pen guide covers common questions. Our guide to doses in a single pen is a quick companion read.

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