Tirzepatide USPI — what the US prescribing information means for UK patients

Step 1, understand what the USPI is and why it is not your reference

Eli Lilly publishes the USPI as a mandatory regulatory document for the US Food and Drug Administration (FDA). It covers the approved indications, dosing, contraindications and safety data as the FDA has reviewed them for the American market. It is written for US healthcare professionals and reflects US regulatory decisions.

In the UK, medicines are licensed by the MHRA, not the FDA. The tirzepatide document that carries legal authority here is the SmPC, a formally different file, approved by the MHRA as part of Mounjaro's UK marketing authorisation. The two documents overlap considerably because they draw on the same clinical trial programme, but the licensed indications, presentation formats and certain safety communications differ. Relying on the USPI for a UK prescription would be like consulting the highway code of a different country: useful background, but not the one your prescriber is legally following. The tirzepatide overview page covers the UK-specific licence in plain language.

Worth noting: the USPI is also where the US brand name Zepbound appears, because that is the FDA-approved weight-management brand in the US. Zepbound does not exist as a UK product. In the UK, tirzepatide for weight management is Mounjaro, and if you are trying to decide whether to think of this medicine as Mounjaro or tirzepatide, the two names refer to the same drug under different contexts.

Step 2, locate the correct UK prescribing document

The authoritative UK reference for tirzepatide is the SmPC hosted on the electronic Medicines Compendium (eMC) at medicines.org.uk. This is freely searchable and publicly available. It carries the MHRA-approved text covering licensed indications, dosing schedule, contraindications, special warnings, interactions, storage conditions and more. Patients are directed to the shorter Patient Information Leaflet (PIL), which is supplied inside every Mounjaro carton and mirrors the SmPC in accessible language.

NICE has also published its own assessment of tirzepatide (Technology Appraisal TA1026) which sets out the criteria under which tirzepatide is recommended for NHS use in England. NICE's guidance on tirzepatide (TA1026) is the document that defines NHS eligibility thresholds; it is worth reading if you want to understand where the NHS access criteria come from. For private prescriptions, eligibility is assessed against the licensed SmPC criteria, which is a wider population than the NHS cohort.

The tirzepatide patient information page on this site walks through the PIL content in practical terms if you prefer a guided explanation rather than the regulatory document itself.

Step 3, understand the key UK-specific facts the SmPC sets out

Several points in the UK SmPC are worth understanding before a consultation. Tirzepatide is supplied as a pre-filled KwikPen; each pen contains four weekly doses. Treatment begins at 2.5 mg (a dose designed primarily to allow the body to adjust rather than to deliver full therapeutic effect) and a prescriber titrates upward through six available strengths (2.5, 5, 7.5, 10, 12.5 and 15 mg), typically at four-week intervals, based on tolerability and response. Your prescriber decides the pace, not the document.

The pen is kept in the fridge, most patients store it in the door, which works well provided the temperature stays between 2 °C and 8 °C. For the exact room-temperature window (for days when refrigeration is not available), the PIL is the definitive reference; the SmPC specifies this, and it should not be paraphrased.

The UK licence covers adults with a BMI of 30 or above, or a BMI of 27 or above alongside at least one weight-related condition such as high blood pressure, type 2 diabetes or high cholesterol. Tirzepatide also carries a UK licence for type 2 diabetes management. On this site, the tirzepatide licence page sets out both indications and what they mean in practice. The free consultation is the right starting point if you want a prescriber to assess whether you meet criteria.

Step 4, apply the right safety information for a UK context

The safety profile described in the UK SmPC is consistent with the USPI because both draw on the same SURMOUNT clinical trial programme. Common side effects are gastrointestinal: nausea, loose stools, constipation, indigestion and reduced appetite tend to be most noticeable in the early weeks of treatment or after a dose increase, then ease for most people. Less common but important signals include gallbladder-related symptoms and, as the NHS notes on its tirzepatide medicines page, signs that should prompt urgent medical attention, severe abdominal pain that radiates to the back warrants same-day assessment given the known association between GLP-1 medicines and pancreatitis.

Women taking oral contraceptives should use an additional non-oral method for the first four weeks of tirzepatide treatment and for four weeks after each dose increase, because tirzepatide can reduce pill absorption. This is a UK-specific clinical recommendation to discuss with your prescriber. Anyone who is pregnant, breastfeeding or planning a pregnancy should not use tirzepatide; under-18s are outside the licensed population. If you are comparing the cost of treatment as you research, the Mounjaro cost page sets out what private prices typically include. Suspected side effects can be reported directly to the MHRA via the Yellow Card scheme.