If you're weighing up the Mounjaro pen vs Wegovy pen, the short answer is that they look alike but work differently. Both are once-weekly, four-dose pens, but they hold different medicines, and the routine differs: needles, priming, dosing, hold time and storage.
This article is information only, not medical advice. Mounjaro and Wegovy are prescription-only medicines, and a qualified prescriber decides whether either suits you. Details come from each pen's emc leaflet and instructions, checked September 2026; the leaflet in your box has the final word.
Mounjaro pen vs Wegovy pen at a glance
| Feature | Mounjaro KwikPen | Wegovy FlexTouch |
|---|---|---|
| Medicine | Tirzepatide (Eli Lilly) | Semaglutide (Novo Nordisk) |
| Strengths | Six, 2.5 to 15 mg | Five, 0.25 to 2.4 mg |
| Needles in pack | No | Yes, 4 |
| Air check | Prime before every injection | Flow check with each new pen |
| Setting the dose | Turn the knob until it stops | Dial until the counter stops at your dose |
| Hold | Slow count of 5 | Slow count of 6 once the counter shows 0 |
| Once started | 30 days from first use (can be kept up to 30 °C) | 6 weeks below 30 °C or in the fridge |
| Missed dose | Inject within 4 days, or skip | Inject within 5 days, or skip |
Either way, never double up; you can move your injection day if at least 3 days have passed since the last dose. Missed more than one dose? Ask your prescriber before restarting; for Wegovy, the prescribing information says a lower restart dose should be considered.
Two different medicines in similar pens
Mounjaro contains tirzepatide, which acts on two gut-hormone receptors, GIP and GLP-1; Wegovy contains semaglutide, which acts on GLP-1 only. A dose number on one pen tells you nothing about the other. Our Mounjaro pen and Wegovy pen pages have more on each.
Don't use the two together: the Wegovy prescribing information advises against combining it with any other GLP-1 receptor agonist, tirzepatide included. Neither leaflet explains switching, so your prescriber plans any switch, including its starting dose.
Needles: in the box, or supplied separately
A Wegovy pack holds one pen and four NovoFine Plus needles, one per dose; the pen is designed for NovoFine Plus, NovoFine or NovoTwist needles up to 8 mm. Mounjaro KwikPen packs contain none: the KwikPen instructions for use ask for a KwikPen-compatible needle and say to check with your doctor, pharmacist or nurse which one.
Otherwise the rules match: a new needle every time, removed straight afterwards, and never share a pen, even with a fresh needle. See our needle size and disposal guide.
Priming every week vs a flow check once per pen
Mounjaro: priming is part of every injection. With a new needle on, turn the dose knob until you hear 2 clicks and an extended line shows in the window. Hold it needle-up, tap gently so air bubbles rise to the top, then push the knob in and slowly count to 5. A little medicine at the needle tip means it's primed. If none appears, try twice more, then once with a new needle; if there's still nothing, the instructions say to contact Lilly, the maker.
Wegovy: check the flow only before the first injection with each new pen. Turn the dose selector to the flow check symbol, hold the pen needle-up and press the button until the counter returns to 0. A drop should appear at the needle tip; if not, check again (twice at most), then once with a new needle; if there's still no drop, the leaflet says not to use the pen.
Setting the dose and holding the pen in place
Mounjaro: turn the dose knob until it stops and the full-dose icon shows. Insert the needle, push the knob in until it stops and slowly count to 5, then check the dose window. If the dose didn't finish, put the needle back in and complete it, but don't redial. If you still think you missed some, don't start again or repeat the injection.
Wegovy: the FlexTouch is a dial-a-dose pen, but each holds one strength. Turn the selector until the counter stops at your prescribed dose, without counting clicks. Keep the counter visible, press the button until it shows 0, then keep pressing and slowly count to 6. Lift off early and a stream of medicine may come out, so you won't get the full dose; ask your pharmacist or prescriber rather than injecting again.
If a KwikPen won't turn to the full-dose icon, or a FlexTouch counter stops short of your dose, there isn't enough for a full dose: dispose of the pen rather than using the leftover. Both use the stomach, thigh or upper arm, but the Mounjaro instructions say someone else should give a back-of-arm injection; our using your pen guide covers rotation.
Storage: 30 days or 6 weeks
Before first use, both pens live in the fridge at 2–8 °C and must never be frozen. Once started, a KwikPen can be kept unrefrigerated at not above 30 °C, and must be thrown away 30 days after first use wherever you keep it; a FlexTouch can be kept for 6 weeks below 30 °C or in the fridge, cap on to protect it from light.
Write the start date on the carton. See our guides to storing weight-loss pens and travelling with a pen.
What about the single-dose Wegovy 7.2 mg pen?
The MHRA approved a single-dose 7.2 mg Wegovy pen on 14 April 2026 for adults with obesity (BMI 30 or more). Its needle is built in and hidden: you press the pen against the skin until a yellow bar stops moving, then throw it away. It can be kept unrefrigerated for up to 28 days at not above 30 °C (7.2 mg leaflet). The 7.2 mg dose can also be given as three 2.4 mg FlexTouch injections on one day, at least 5 cm apart and each with a new needle; partly used pens then go back in the fridge, needle off (Wegovy leaflet).
Is one pen easier to use?
Ease of use isn't a reason to choose a medicine; that's your prescriber's call. With either pen, ask your pharmacist for a demonstration and reread the instructions with each new pen.
Most side effects come from the medicine rather than the pen, though both leaflets list injection-site reactions as common. Nausea, diarrhoea, vomiting and constipation are among the most common. Stop the medicine and get urgent medical help for severe, persistent stomach pain. See our side effects page, and report suspected side effects through the MHRA Yellow Card scheme.
Frequently asked questions
Is the Mounjaro pen the same as the Wegovy pen?
No. Both are once-weekly, four-dose pens, but they hold different medicines from different makers. The KwikPen is primed before every injection; the FlexTouch gets a flow check only with each new pen.
Do I need to prime my Mounjaro pen every week?
Yes, according to the UK instructions for use. With a new needle on, turn the dose knob to the prime position (2 clicks), hold the pen needle-up and push the knob in for a slow count of 5, into the air, not your body. A little medicine should appear at the tip.
Does the Mounjaro pen come with needles?
No. KwikPen packs don't include them. Use a KwikPen-compatible needle and ask your doctor, pharmacist or nurse which one. Wegovy FlexTouch packs include four NovoFine Plus needles.
Which pen lasts longer once started?
A Wegovy FlexTouch can be used for 6 weeks, stored below 30 °C or in the fridge. A Mounjaro KwikPen can be kept out of the fridge at not above 30 °C but must be thrown away 30 days after first use. Neither may be frozen.
Can I switch from a Wegovy pen to a Mounjaro pen?
Only if your prescriber decides it's appropriate, and never use both at once. The medicines and doses differ and neither leaflet explains switching, so your prescriber sets the plan.