Tirzepatide mixing charts explained — and why they don't apply to licensed Mounjaro

Where mixing charts come from, and the regulatory picture in the UK

Tirzepatide mixing charts originate in the United States, where compounding pharmacies have produced tirzepatide from raw peptide powder for self-injection. That process involves reconstituting lyophilised (freeze-dried) tirzepatide with bacteriostatic water, then calculating a dose from the resulting solution's concentration. If you want to understand the full process, a tirzepatide peptide mixing chart illustrates how volumes are mapped to doses for a given vial strength.

None of that applies to the UK's licensed supply. The MHRA licenses Mounjaro as a finished, pre-filled KwikPen, Eli Lilly manufactures it to pharmaceutical standards, fills each pen to the correct concentration and packs four weekly doses into a single device. You click the pen, inject subcutaneously into the abdomen, thigh or upper arm, and the dose is done. There is no syringe to load and nothing to calculate.

The broader concern is that content about mixing charts is intertwined with guides for sourcing unlicensed tirzepatide online. The MHRA has been clear: tirzepatide is a prescription-only medicine, and preparations sold without a valid UK prescription fall outside the regulated supply chain. The MHRA's Yellow Card scheme accepts reports of suspect sellers and unlicensed products, a practical step anyone can take if they encounter a seller offering tirzepatide that doesn't require a prescription. You can read more about the licensed treatment and how it works on the Mounjaro information page.

What the clinical evidence shows about licensed tirzepatide

The reason tirzepatide attracts such intense interest is straightforward: the trial results are genuinely impressive. In SURMOUNT-1, published in the New England Journal of Medicine, adults with obesity taking the 15 mg dose achieved an average body-weight reduction of around 20–21% over 72 weeks alongside a reduced-calorie diet and increased physical activity. SURMOUNT-5, a head-to-head comparison published in 2025, found tirzepatide produced greater average weight loss than semaglutide 2.4 mg over the same period.

These results were achieved with pharmaceutical-grade, pre-filled licensed product, administered at doses titrated by a prescriber in a controlled research setting. The strength, purity and sterility of the product were guaranteed by the manufacturer. Compounded preparations lack that assurance, potency, sterility and concentration can all vary, and a mixing error that results in a ten-fold overdose is not a theoretical risk. It has happened with similar injectable preparations, and our page on mixing tirzepatide explains exactly why those risks arise and what makes the licensed pen a safer alternative. Worth keeping in mind when a chart looks deceptively simple.

NICE reviewed this evidence base in full when publishing its guidance on tirzepatide (TA1026), recommending it for adults within defined eligibility criteria. That recommendation applies to Mounjaro specifically, dispensed through a licensed pharmacy against a UK prescription. You can find an overview of the eligibility thresholds on the tirzepatide treatment page.

How licensed Mounjaro is actually used, what the pen replaces

Because mixing charts assume a multi-step preparation process, it's useful to lay out exactly what the licensed pen does instead. Each Mounjaro KwikPen holds four doses at a fixed strength: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg or 15 mg. Treatment typically starts at 2.5 mg (a dose designed to let the body adjust rather than to achieve maximum effect immediately) and is titrated upward by the prescriber, usually in four-week steps, with our tirzepatide chart showing how those dose stages progress across the treatment timeline.

Before an injection, the pen stays refrigerated between 2–8°C. Many people keep it in the fridge door, which is fine so long as the temperature is consistent. The Mounjaro Patient Information Leaflet (available via the eMC) sets out the exact room-temperature storage window, it's worth reading that section carefully rather than relying on second-hand summaries. Injections go into the abdomen, thigh or upper arm, rotating sites from week to week.

There is no mixing, no vial to reconstitute and no chart to consult. If a seller's instructions include any of those steps, the product is not licensed Mounjaro and should not be used. Questions about injection technique, storage or titration timing are best directed to the prescribing team, and on the faqs page you'll find answers to the practical questions our prescribers hear most often.

Getting tirzepatide legally in the UK

The legal route to tirzepatide in the UK runs through a clinical assessment followed by a prescription from a registered prescriber. For those who don't qualify through the NHS (whose phased eligibility criteria are strict and still being rolled out) a regulated private pharmacy is the alternative. You can check whether any online pharmacy is properly registered using the GPhC register; GPhC premises registration number 9012878 is how you'd verify nume specifically.

At nume, a GPhC-registered Independent Prescriber reads your consultation the same day. There is no algorithm making the call. If treatment is clinically appropriate, the pen is dispatched in plain packaging for next-working-day tracked delivery, no prescription to arrange separately, no delivery fee, no subscription. If you'd like to know whether tirzepatide might be suitable for you, checking your eligibility starts with a free consultation. You can also get an honest sense of what private treatment costs on the Mounjaro cost page before you decide.