Why Can't I Get the Last Dose of Mounjaro? (October 2026)

01 · The short answer

What is actually happening when the dial won't turn

The pen is doing what it was designed to do. A Mounjaro KwikPen contains four weekly doses, and you set each dose by turning the knob until the correct number shows in the dose window.¹³

So when the window refuses to reach your dose, the pen no longer holds enough for one full injection. The correct response is not to push harder.

We cover related situations in our guides to the last dose of a Mounjaro pen and a pen that seems stuck on its last dose.

02 · Before you worry

What to check first

Start with your own count, because that is the most common explanation. Each pen is four weekly injections, so four weeks of injections empties it. Four doses taken on the same weekday take 28 days, which sits inside the 30 days a pen may be kept out of the fridge at a temperature not above 30°C once in use.¹

• Count injections, not weeks. Check your calendar or a tracking app such as GLPTrackr. A missed or delayed week means the pen may be on its fourth dose later than you expected.
• Confirm the number in the window.
• Check the pen is the strength you think. Look at the label and carton against your prescription.
• Look at your dose history. If you have already taken four injections from the pen, the pen is finished, however it looks.

If you have taken fewer than four injections and the window still will not reach your dose, stop using the pen and contact the pharmacy that supplied it. You can also report a suspected defective product through the Yellow Card scheme.¹⁹

03 · Your next step

What to do next, depending on your situation

If you want to see how stock and delivery work, you can review the Mounjaro pen prices and consultation page. Doses from 2.5mg to 15mg are in stock, and same-day dispatch applies when you order by 3pm.

04 · Planning ahead

How to avoid running out on injection day

The simplest fix is to order the next pen a week or so before you inject the final dose from the current one. Repeat orders re-check suitability and there is no auto-shipping, so the reorder is yours to trigger. Delivery is free next-day tracked in temperature-controlled packaging.

A 5mg pen has a standard price of £218.99 for four weeks, and every later order is £25 off the standard price. A new customer's first order is £40 off with code FIRST40, at any dose. The reorder discount applies automatically (code DOSE25).

Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. You can start your free consultation online.

05 · Why not force the last dose

Why you should not force the pen

Do not force the dial.

Read the complete UK last-dose guide for more detail.

06 · If your next pen is late

If your next pen is late: the missed-dose rule

If injection day arrives and you have no pen, the licensed missed-dose rule applies. Take the dose as soon as you can within 4 days (96 hours) of the scheduled time, then carry on with your usual day.¹³ 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

That 4-day window is why a quick call to the pharmacy matters. A delayed delivery can often still be absorbed without any missed dose at all.

You can also change your injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.¹³ That may help if a new pen arrives a day or two after your usual day.

If you are unsure which situation applies, the prescribing team can advise. Support runs Monday to Friday, 9am to 5pm, by email at support@everydaymeds.co.uk, through account portal chat, or by phone on 0333 207 0413.

07 · Using the pen correctly

Using each dose correctly from the pen

Good technique prevents most confusion about what is left. 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. Follow the pen's own instructions for the injection steps.

There is no best time of day. Mounjaro works the same morning or evening, so what matters is keeping to the same day each week.¹³ Many people pick a weekend morning so that early side effects fall on days off.

Write the date of each injection somewhere you will see it. A simple tally on the carton means that on injection four you know the pen is meant to be finished. Our guides on taking the final dose from a pen and the last shot in a pen walk through this routine.

08 · Storage and expiry

Storage: keeping a pen usable until it is empty

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, and must then be thrown away.¹³ Keep the cap on to protect the pen from light. Do not use a pen that has been above 30°C or has been frozen.

Four weekly doses fit comfortably inside that 30 days if you inject on schedule. A delayed injection, though, can push the final dose past the in-use limit. If that happens, discard the pen rather than push on, and talk to the pharmacy about a replacement.

Unopened pens stay in the fridge until first use 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

09 · Stopping and the washout

What a gap in treatment means

A short gap between pens is not an emergency, but it is worth understanding. Tirzepatide has a half-life of about five days, so 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

That is why one late dose is usually manageable, while a long break should be discussed with your prescriber. If you restart after a long gap, ask the prescribing team which dose to resume on rather than guessing.

Remember also that results are gradual by design. 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.¹¹ Treatment works alongside a reduced-calorie diet and increased physical activity.

10 · Genuine pens and supply

Why a genuine pen matters

A pen that behaves oddly is a good reason to check where it came from. Counterfeit and unregulated weight-loss injections are a known risk, and the MHRA publishes counterfeit medicine alerts.⁷ Be wary of any seller offering to supply without a consultation or prescription.

EverydayMeds is a GPhC-registered UK online pharmacy (registration 9012878) and supplies genuine KwikPens through official LillyDirect supply, direct from Eli Lilly's UK distribution. Every order includes needles, a sharps bin and injection guidance. Dispensed prescription medicines cannot be returned except when faulty, damaged or the wrong item, so contact us within 3 days if something is wrong with a pen on arrival.