Eli Lilly Mounjaro KwikPen: How It Works (October 2026)

01 · The device

What is the Eli Lilly Mounjaro KwikPen?

The KwikPen is a pre-filled pen that delivers tirzepatide under the skin once a week. Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine made by Eli Lilly, licensed in the UK for weight management in adults and for type 2 diabetes.¹ It comes as a pre-filled multi-dose pen (KwikPen) in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹

You do not need to draw anything up or measure. The pen is the whole system. The Lilly Mounjaro pen page has more on the pen.

02 · Your next step

Is this relevant to me, and what next?

If you are still deciding on treatment, start with a free online consultation, reviewed by a GPhC-registered prescriber. Your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99), and you can see every dose on the Mounjaro pen prices and consultation page. Needles, a sharps bin and injection guidance are included with every order. To check the source of any pen you hold, read how to tell real from fake Mounjaro.

03 · Injecting and sites

Injecting with the KwikPen

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.¹ 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.¹ Follow the pen's instructions for the injection itself. Our genuine KwikPen needles guide covers what ships with your order.

04 · Storage and travel

Storing and travelling with your pen

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 — useful for short trips — and must then be thrown away.¹ Keep the pen cap on to protect it from light, and never use a pen that has been frozen.¹³

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.¹³ Unopened pens should be kept in the fridge until the expiry date printed on the box.

05 · If the pen malfunctions

What to do if a Lilly pen seems to malfunction

Stop and do not try to work around the problem. Check the pen against the patient information leaflet, then contact the pharmacy that supplied it. Never use a pen that has been above 30°C or frozen.

Our support team is available Monday to Friday, and we can advise on faulty, damaged or wrong items. Our dedicated page on Mounjaro pen malfunction goes through the common situations. Supply matters too: see where to get authentic Eli Lilly Mounjaro.