Your Mounjaro pen has a cherry-coloured label — here's what that tells you

You've opened the box and spotted a cherry-red label, now what?

Picture this: your Mounjaro delivery arrives, you open the plain outer packaging, and the pen label is a deep cherry red. If you were expecting a grey label from your starter pen, that pause is understandable. The colour change is intentional. Eli Lilly colour-codes every Mounjaro strength so that picking up the wrong pen at the back of the fridge door is less likely, a small but meaningful safety feature for anyone who has more than one strength at home during a transition.

Cherry is the assigned colour for 5 mg tirzepatide. The 2.5 mg pen is grey, and the higher doses each carry their own distinct colour. The full Mounjaro overview covers the complete range of six licensed UK strengths. The colour system runs across both the KwikPen cap and the label, so it is visible even when the pen is stored upright. Confirming your strength before each weekly injection is a good habit regardless, cross-check the number printed on the label alongside the colour.

If your cherry pen arrived and you were not expecting it, the right move is to contact your prescriber before injecting. At nume, our support team is available seven days a week for exactly this kind of query.

Why 2.5 mg comes first and 5 mg follows, the reasoning behind tirzepatide's dose steps

The 2.5 mg starting pen exists for one reason: to help your system adjust. Tirzepatide slows gastric emptying and reduces appetite through two receptor pathways (GIP and GLP-1) and that activity can cause nausea or digestive discomfort in the first weeks, especially at higher doses. Starting low gives those effects the best chance of staying manageable. The NHS tirzepatide page describes this tolerability rationale clearly for patients.

After roughly four weeks, a prescriber reviews how the first pen was tolerated. If things have settled, the next step is 5 mg, the cherry pen. This is not a sudden jump in clinical effect; it is a measured increase intended to build on the initial adjustment. Many people find the transition straightforward. Others need a little longer at 2.5 mg, and a good prescriber will say so rather than push the schedule for its own sake.

The cherry 5 mg pen is also a KwikPen containing four weekly doses, used the same way as the starter: subcutaneous injection into the abdomen, thigh or upper arm, rotating sites each week. Exact technique is covered in the Patient Information Leaflet included with your pen. Questions about whether your dose is working well are best brought to your prescriber rather than resolved by adjusting the schedule yourself.

Side effects at the 5 mg stage and when to seek help

The side-effect profile at 5 mg is broadly the same GI-led pattern documented across the SURMOUNT clinical programme and summarised on the NHS medicines page for tirzepatide: nausea, loose stools, constipation, indigestion and reduced appetite. These are most noticeable in the days after a new dose, and they tend to ease as the weeks pass.

A small number of people experience more than mild discomfort. Severe, persistent stomach pain that radiates toward the back (with or without vomiting) needs urgent medical attention; this can be a sign of pancreatitis, and the MHRA has specifically highlighted it as a serious but infrequent risk with GLP-1 medicines. Do not wait it out. Call 111 or go to A&E.

Other symptoms that should not be ignored include signs of a serious allergic reaction, significant dizziness, or anything that simply feels wrong and persists. Our guide to chest pain and Mounjaro and the page on blurred vision while on tirzepatide cover two questions our prescribers hear regularly, and if you are specifically concerned about cardiac symptoms our detailed resource on chest pains and Mounjaro explains what to watch for and when to act. Patients and carers can also report suspected side effects directly through the MHRA Yellow Card scheme.

Storage, travel and staying on track with your cherry pen

Every Mounjaro pen, cherry or otherwise, is stored in the fridge at 2°C to 8°C. The pen can sit at room temperature for a limited period if you are away from home, but the exact window is stated in the Patient Information Leaflet rather than here, the leaflet is the authoritative source and varies slightly between batches. Keep the pen in its original packaging away from light.

If you are planning to travel with your cherry pen, the rules around carrying prescription medicines on flights are worth reading before you pack. The dedicated page on taking Mounjaro on a plane covers what documentation helps and how to keep the pen cool in transit.

For context on what private treatment involves cost-wise, the Mounjaro cost page sets out how pricing works across dose stages, including what a legitimate private service should include beyond the pen itself. At nume, one price covers the clinical review, the prescription and tracked next-working-day delivery, no extras added at checkout.

Ready to discuss whether tirzepatide is right for you? Start your free consultation and a GPhC-registered prescriber will review your answers the same day.