How to Prime a Mounjaro Pen: UK Guide (October 2026)

01 · The core answer

How priming fits into your weekly Mounjaro injection

Priming is a preparation step done after you attach a fresh needle and before you dial and inject your dose. The exact sequence is set out in the Instructions for Use that come with your pen, and that leaflet is the authority.¹³

So a sensible routine looks like this:

• Take the pen out of the fridge and check the label shows the strength you were prescribed.
• Wash your hands and read the Instructions for Use if it is your first pen or a new strength.
• Attach a new needle, then complete the priming step as your leaflet shows.
• Dial your dose, check the number in the window, and inject under the skin.
• Remove the needle, replace the pen cap and store the pen correctly.

Rotate the injection site with each dose. 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.¹

02 · Your next step

Is priming relevant to you, and what should you do next?

If you are about to inject for the first time, or you have just received a new strength, yes. Read the leaflet before the injection day, not during it. If you are unsure about any step, our pharmacy team can help, and so can your own pharmacist. For more depth, see our guides on Mounjaro priming and preparing your Mounjaro pen.

If you are still choosing a provider, the Mounjaro pen and consultation page shows live prices; the 2.5mg starting pen is £169.99 at the standard price. Needles, a sharps bin and injection guidance are included with every order.

03 · Why we don't list click counts

Why you should never rely on counting clicks

The most common mistake in online priming advice is treating clicks as the measure. Clicks can help you feel the knob move, but they are not how the dose is confirmed.

Your leaflet describes your pen, so use it rather than a click count for priming or dosing. Different guides give different answers, and some describe other devices.

The same logic answers a common question: how many clicks give a lower dose from a higher-strength pen? The answer is that you should not try. Each pen is made for its strength. If your prescriber wants you on a different strength, they will prescribe the matching pen.

04 · Pen won't prime or dial

Why won't my Mounjaro pen prime or turn?

A pen that will not prime or turn needs checking, not forcing. Start with the basics before assuming it is faulty:

• Needle: check it is a fresh needle, fitted securely and with the outer shield removed as the leaflet describes.
• Dose knob: make sure you are turning it in the direction shown in your Instructions for Use, and that you have not already dialled a dose.
• Storage: a pen that has been frozen must not be used. Pens belong in the fridge at 2–8°C and must never be frozen.

Do not top up from a second pen, and do not try to squeeze out the last drops.

If a new needle and a careful read of the leaflet do not fix it, contact the pharmacy that supplied the pen. If you think a pen is defective, you can also report it through the Yellow Card scheme.¹⁹ Our support team is available Monday to Friday, 9am to 5pm, on 0333 207 0413 or at support@everydaymeds.co.uk, and dispensed medicines can be returned if the item is faulty, damaged or wrong (contact us within 3 days).

05 · If you forgot to prime

What happens if you forgot to prime your Mounjaro pen?

If you realise before injecting, stop and go back to the leaflet. Do not carry on and hope for the best. If you realise afterwards, do not repeat the injection to make up for it. Repeating a dose risks taking more than prescribed, and the licensed rule is firm: never take two doses within 3 days of each other.¹

Contact your pharmacist or prescriber, tell them what happened and let them advise. Do not invent a workaround such as an extra dose.

Many readers worry that a missed step means a missed week. The missed dose rule is the guide here: 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.¹

For more detail, read our guides on forgetting to prime a Mounjaro pen and what happens if you don't prime Mounjaro.

06 · Every time or only once

Do you prime the pen every time?

The answer sits in your Instructions for Use, which set out when the priming step applies to your pen and when it does not.¹³

A practical habit helps: keep the leaflet in the pen carton, and glance at the steps before each injection until the routine is automatic. Our related guides cover this in more depth: do you have to prime Mounjaro each time and do you prime a Mounjaro pen every time.

If you collect your pen from a high-street pharmacy, you can also ask them about priming. Our guide to pharmacy help with priming Mounjaro explains what to ask.

07 · Pen life and storage

How many doses are in a pen, and how long does it last?

Each KwikPen contains four weekly doses.¹ People sometimes feel they get fewer than expected, or wonder how much is left after the fourth dose.

Priming is not a reason to expect fewer doses from a correctly used pen. If you consistently get fewer doses than the pen should supply, tell your pharmacy and keep the pen so it can be checked.

Storage affects whether the pen works as intended. 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, 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.¹

For unopened pens, keep them in the fridge until first use and they 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, because figures circulating online often come from other countries' labels.¹

08 · Timing and routine

What is the best time of day to take Mounjaro?

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.¹

Build priming into that routine so it never feels rushed. Set out the pen, a new needle and your sharps bin before you start, and give yourself a few unhurried minutes. Rushed injections are where skipped steps tend to happen.

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 If you do, mark the new day in a calendar or in the free GLPTrackr companion app so the gap is never accidentally too short.

09 · Travel and out of the fridge

Carrying and using your pen when travelling

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.¹

Pack spare needles and a travel sharps option, and read your leaflet before you go so you are not working out the preparation steps in an airport toilet or hotel room. Check destination rules for travelling with prescription injectables before you fly.

10 · Dose ladder context

Priming and the dose ladder

Everyone starts Mounjaro 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 (7.5mg, 10mg, 12.5mg) up to a maximum of 15mg weekly, depending on how you respond and tolerate it.¹ Each step means a new pen with a different strength on the label.

That is a good moment to reread the leaflet and check the strength before you dial. Never try to build a different dose out of the wrong pen.

For more practical advice, see our priming Mounjaro pen tips and the week by week priming guide. If your pen's physical size matters for storage or travel, our note on Mounjaro pen dimensions may help.

11 · Ordering with support

Getting a pen with proper support

If you are thinking of starting treatment, here is how ordering works with us. Our weight loss clinic explains the wider service.

• Free online consultation: a short health questionnaire, with no charge and no obligation.
• Prescriber review: reviewed by a GPhC-registered prescriber. 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: same-day dispatch when ordered by 3pm, then free next-day tracked delivery in temperature-controlled packaging. Saturday delivery is £14.99.

Our pens come through official LillyDirect supply, directly from Eli Lilly's UK distribution. Ongoing monthly reviews are included, and the prescribing team can help with side effects. New customers save £40 on their first order with code FIRST40, and an automatic £25 reorder discount applies to every future order (code DOSE25). All six doses are in stock. Prices checked 11 October 2026.