What dose of Mounjaro do you start on?

What the licensed schedule says about where to begin

The Mounjaro SmPC, published on the electronic Medicines Compendium, is unambiguous: 2.5 mg once weekly is the starting dose for all adults, and it stays there for at least four weeks before any increase is considered. The NHS tirzepatide page describes the same schedule. This is worth knowing because people sometimes arrive at a consultation assuming that a higher body weight means a higher starting point, it does not. The licensed entry point is fixed.

The reason is pharmacological rather than cautious bureaucracy. Tirzepatide activates two gut-hormone receptors simultaneously (GIP and GLP-1), which slows gastric emptying and reduces appetite. Starting at a lower dose lets your digestive system adapt; the most common side effects (nausea, loose stools, reflux) are typically most noticeable in the early weeks and settle as tolerance builds. Beginning at 5 mg or above meaningfully increases the risk of those symptoms being severe enough to disrupt daily life. The starter dose exists to make the rest of the journey manageable. There is a dedicated page on whether the 2.5 mg starting dose is mandatory if you want more detail on that specific question.

One thing our prescribers hear fairly often: people who have done a lot of research before their consultation are sometimes frustrated that the first pen is not the one that produces the most noticeable results. That is an entirely reasonable feeling. The 2.5 mg phase is a foundation, not the treatment ceiling.

How dose increases are structured from 2.5 mg upwards

After the initial four weeks, a prescriber can increase the dose to 5 mg for the next four-week period, then 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg, each step separated by a minimum of four weeks. The pace is not automatic. Before a dose increase, a clinician reviews whether you have tolerated the current dose, checks your progress, and assesses whether moving up is appropriate. At 5 mg, many people begin to notice a more marked reduction in appetite; the therapeutic effect builds as the dose climbs.

Not everyone will reach 15 mg, and that is not a failure. Some people find 7.5 mg or 10 mg is the highest dose their system tolerates comfortably, and clinical guidance supports staying at that level if it is working. What matters is the highest well-tolerated dose, not the highest available one. The SURMOUNT-1 trial, published in the New England Journal of Medicine, reported average weight reductions of around 20–21% at 15 mg over 72 weeks in adults with obesity (the figures that set expectations for the top of the ladder) but meaningful reductions were observed at every maintenance dose studied. If you are wondering what happens if treatment begins at 5 mg rather than following the standard schedule, the evidence on that question is worth reading separately.

The Mounjaro KwikPen is supplied as a four-week pack at each strength. Each pen delivers four weekly doses, so one pen covers one step of the titration. Storage is refrigerated (2–8°C); the Patient Information Leaflet sets out the exact room-temperature window, and that is the definitive reference, not secondary sources.

Private versus NHS: does the starting dose differ?

No. The starting dose is determined by the medicine's licence, not by who is prescribing it. Whether Mounjaro is prescribed through the NHS or privately through a regulated online pharmacy, the 2.5 mg starting point applies. The NICE technology appraisal for tirzepatide (TA1026) recommends the medicine for adults with a BMI of 35 or above alongside at least one weight-related condition, with lower thresholds applying for some ethnic backgrounds, but those criteria govern NHS eligibility, not the dose you begin on.

For people who do not meet the current NHS thresholds, or who would rather not wait, the private route through a clinically reviewed consultation is the alternative. The private licence criteria are broader: BMI 30 or above, or 27 or above with a relevant weight-related condition. Either way, the prescriber's clinical assessment comes before any dose decision, including the first one. You can read more about how Mounjaro works and who it is licensed for on the main Mounjaro page.

One practical note on cost: the Mounjaro price landscape changed significantly when Eli Lilly raised UK list prices from September 2025. If that context is useful, the Eli Lilly price increase page covers what happened and what it means for private prescriptions. At nume, one transparent price covers consultation, prescription, and next-working-day delivery, no separate fees at each dose step.

When to talk to your prescriber about your dose

The titration schedule is a framework, not a rigid countdown. Symptoms that feel unmanageable, a stall in progress, or a change in your health picture are all reasons to contact your clinical team before the four-week mark rather than waiting. Equally, if side effects are mild and you are tolerating the current dose well, the review at week four is straightforward.

What you should never do is adjust your own dose (increase, decrease or skip) based on something you have read online. The prescriber holds the full picture of your history, your concurrent medicines, and your response so far. Questions about what dose to start tirzepatide at, or whether there are circumstances where a different entry point applies, are exactly the kind of thing a consultation is designed to answer properly. Our FAQs cover some of the most common dose-related questions too.

If you are ready to begin, start your free consultation and a GPhC-registered prescriber will review your details the same day.