Key Takeaways
- The Mounjaro KwikPen delivers four weekly doses of tirzepatide; each pen is for single‑patient use only.
- Always check your pen’s batch number. Fake 15 mg pens with batch D873576 have been reported by the MHRA.
- Inject into the abdomen, thigh, or upper arm, and rotate sites each week to reduce skin reactions.
- Follow the standard titration schedule: start at 2.5 mg and increase every 4 weeks as prescribed.
- Store unused pens in the fridge (2–8 °C). After first use, keep at room temperature (up to 30 °C) for up to 30 days.
- Dispose of used pens and needles in an NHS‑compliant sharps bin. Never attempt to extract leftover liquid.
Introduction
To use the Mounjaro KwikPen, first confirm the batch number and strength on the label. Then prepare the pen by attaching a new needle, dial the prescribed dose, inject it into a clean injection site, hold for 10 seconds, and safely dispose of the needle after each use. The entire process takes about two minutes.
In February 2026, the Medicines and Healthcare products Regulatory Agency (MHRA) issued an alert about falsified Mounjaro KwikPen 15 mg pens with batch number D873576 supplied by a single pharmacy in Birmingham. This alert highlights the need to verify your pen’s authenticity before every injection.
Is Your Mounjaro Pen Real? How to Check Before You Use It
Before you use any Mounjaro KwikPen, verify its authenticity. In a Drug Safety Update, the MHRA confirmed that fake 15 mg pens with batch number D873576 were dispensed by The Private Pharmacy Clinic in Birmingham.[1] These pens may contain tirzepatide, but their sterility cannot be guaranteed, and they pose a risk of infection or allergic reaction.[1]
“Fake Mounjaro (tirzepatide) KwikPen 15mg pre‑filled pens with batch number D873576 have been dispensed by The Private Pharmacy Clinic in Birmingham. Patients who have been prescribed a 15mg KwikPen should check the batch number on the pen before use.”[1]
How to check your pen:
- Look at the label on the pen barrel. The batch number (Lot) is printed there.
- If your pen is a 15 mg KwikPen and the batch number is D873576, do not use it.
- If your pen is a 15 mg KwikPen with any other batch number, it is not affected by this alert.
- If you have a 7.5 mg pen (or any other strength), the alert does not apply to you. The batch D873576 is a legitimate batch for 7.5 mg pens.[1]
If you suspect you have a fake pen, stop using it immediately. Email the MHRA at info@mhra.gov.uk with “Mounjaro Pens” in the subject line, and keep the pen in a safe place for collection.[1]
What’s in the Box: Your Mounjaro KwikPen Parts Explained
The Mounjaro KwikPen comes in a carton containing one pre‑filled pen and separate needles. Familiarise yourself with the parts:
- Pen cap – plastic cover that snaps off.
- Dose knob – the dial at the end of the pen; you turn it to select your dose and press it to inject.
- Dose window – shows the number of milligrams you have dialled.
- Needle (supplied separately in a sealed pack) – attach a new needle for each injection.
- Inner needle cap and outer needle cap – protect the needle before use.
Newer versions of the pen (from April 2026 onwards) have a redesigned internal plunger that leaves less visible liquid after the fourth dose. The injection technique is identical.
Preparing for Your First Injection: A 5‑Minute Checklist
Before you inject, complete these steps:
- Wash your hands with soap and water.
- Check the pen’s batch number against the MHRA alert (see above).
- Inspect the pen and the liquid. The solution should be clear and colourless. Do not use if it looks cloudy, discoloured, or contains particles.
- If the pen has been stored in the fridge, let it sit at room temperature for 10–15 minutes. Do not warm it in any other way.
- Choose an injection site (abdomen, thigh, or upper arm) and clean the area with an alcohol wipe. Allow it to dry.
- Have a sharps bin ready for safe disposal of the used needle.
How to Use the Mounjaro Pen: A Step‑by‑Step Guide
Follow these steps as described in the official Patient Information Leaflet (PIL) and Eli Lilly’s manufacturer guidance for the KwikPen.[2]
- Remove the pen cap. Pull it straight off. Do not twist.
- Attach a new needle.
- Peel the protective seal from a new needle.
- Push the needle straight onto the pen and twist clockwise until it is secure.
- Pull off the outer needle cap and then the inner needle cap. Keep the outer cap for removal after injection.
- Prime the pen (first‑time use only).
- Turn the dose knob until it stops at the grey “u” symbol (priming symbol) or the 0 marker, depending on your pen version. (Some pens require a small amount to be expelled before first use.)
- Hold the pen with the needle pointing up, tap the cartridge gently to remove air bubbles, then press the dose knob until a drop of liquid appears at the needle tip.
- If no drop appears, repeat the priming step. If after 3 attempts no drop appears, do not use the pen – contact your prescriber or Eli Lilly for a replacement.
- Dial your dose.
- Turn the dose knob until the number in the window matches the dose prescribed by your clinician (e.g., 2.5 mg for the first month).
- Do not press the dose knob while turning it.
- Inject the dose.
- Insert the needle into your chosen injection site at a 90‑degree angle (or as instructed by your healthcare professional).
- Press the dose knob firmly until it clicks. Keep it pressed and hold the needle in place for 10 seconds.
- Withdraw the needle. A small drop of blood on the site is normal – apply gentle pressure with a dry cotton ball if needed.
- Do not rub the injection site.
- Remove and discard the needle.
- Carefully replace the outer needle cap onto the needle, then unscrew the needle from the pen and drop it directly into your sharps bin.
- Never recap the inner needle cap – this risks needle‑stick injury.
- Replace the pen cap. Store the pen as described in the storage section.
Choosing and Rotating Your Mounjaro Injection Site
Mounjaro is injected into the subcutaneous layer of skin. Approved sites are the abdomen (at least 5 cm from the navel), the front of the