Tirzepatide dosing chart in units: how the Mounjaro schedule works

Step 1, the 2.5 mg pen and why it exists

The titration sequence begins at 2.5 mg once weekly. This is not a therapeutic dose in the sense that it is designed to produce significant weight loss immediately; its job is to let your digestive system adjust to tirzepatide's mechanism before the dose increases. Nausea, the most commonly reported side effect, tends to be most noticeable in the first days after starting or after a step-up, beginning low reduces how sharp that experience is for most people.

A practical check you can do in under a minute: before each new pen, compare the colour band on the label against the dose your prescriber has confirmed. Each Mounjaro strength carries a distinct label colour, so a quick glance confirms you have the right pen in hand. The full tirzepatide overview on our site explains the KwikPen design in more detail.

Clinically, 2.5 mg typically runs for four weeks before the prescriber reviews progress and decides whether to step up. There is no fixed rule that every patient must reach 15 mg, the right maintenance dose is the one that delivers meaningful progress with acceptable tolerability, which varies between individuals.

Step 2, moving through 5 mg, 7.5 mg and 10 mg

After the 2.5 mg introductory pen, the licensed titration continues through 5 mg, 7.5 mg and 10 mg, each typically held for around four weeks. That pacing matters: increasing too quickly raises the likelihood of gastrointestinal side effects including nausea, vomiting, diarrhoea, constipation and indigestion. Staying at a dose long enough for the body to settle is part of what makes the programme work.

At each step, the KwikPen format means there is still no measuring involved, the dose is pre-set. What changes is the strength of the cartridge you receive. For anyone thinking about the cost across the dose ladder, our page on Mounjaro pricing in the UK covers how private costs compare across providers and doses, with the context you need to read a price honestly.

The NHS information on tirzepatide (NHS medicines: tirzepatide) summarises the expected side-effect profile at each phase of treatment and what to do if GI symptoms become difficult to manage, worth bookmarking alongside your Patient Information Leaflet.

Step 3 (reaching 12.5 mg and 15 mg

The upper two doses) 12.5 mg and 15 mg, are where SURMOUNT-1 trial participants saw the most substantial average weight reductions. In that trial, involving 2,539 adults with obesity and without diabetes, the 15 mg dose group achieved around 20–21% average body-weight reduction over 72 weeks, as published in the New England Journal of Medicine. Not every patient reaches 15 mg, and that is not a failure. NICE guidance (TA1026) notes that continuing treatment should be reviewed if less than 5% weight loss has been achieved after six months at the highest tolerated dose.

Dose increases at this stage follow the same prescriber-led review process. At nume, every repeat order (including a dose step-up) is reviewed by a GPhC-registered Independent Prescriber before dispatch; evidence of progress is part of that review. The Mounjaro dosing chart on our site maps these upper steps alongside the eligibility picture.

Storage remains the same across all strengths: refrigerated at 2–8°C. The exact room-temperature window allowed if a pen is temporarily out of the fridge is specified in the Patient Information Leaflet; never rely on a general estimate.

What a 'units' search actually means, and why it matters

Searches for tirzepatide dosing in units often arise from confusion with insulin, a medicine that genuinely is measured and drawn up in units using a syringe. Tirzepatide works differently. As a dual GIP and GLP-1 receptor agonist, it is formulated in milligrams, supplied in a pre-loaded pen, and requires no drawing up, no unit counting and no calculation. Someone arriving from an insulin background, or who has seen compounded tirzepatide described online, may encounter unit-based references, but those do not apply to licensed Mounjaro KwikPens in the UK.

Compounded or unlicensed tirzepatide is not the same product and is not available through any UK-regulated pharmacy. The MHRA has repeatedly warned about products sold without a valid prescription and without clinical oversight, fake or unlicensed pens have caused serious harm. If a dosing chart you find asks you to measure in units with a syringe, it does not relate to licensed UK Mounjaro. The peptide dosing chart context page on our site addresses this distinction directly for readers who have encountered compounded versions.

For dose-specific detail on how weight-loss titration maps to clinical outcomes, the tirzepatide dosing for weight loss page covers the evidence behind each step.