What are the doses of tirzepatide — and how does the schedule work?

You've just been prescribed Mounjaro, and you're wondering why it starts so low

Picture this: your consultation has been approved, the pen arrives the next morning, and the label says 2.5 mg. You've read the trial results (around 20% average body-weight reduction at the highest dose in SURMOUNT-1, published in the New England Journal of Medicine) and 2.5 mg feels a long way from there. It is, intentionally.

The opening pen's job is adjustment, not weight loss. Tirzepatide activates both GIP and GLP-1 receptors, which slows gastric emptying and reduces appetite. That action is exactly what produces results over time, but it also brings the GI side effects most people have heard about, nausea, loose stools, reflux. Starting low gives your system a chance to settle before the dose moves anywhere near the therapeutic range.

Most people spend about four weeks at 2.5 mg, then move to 5 mg. A question our prescribers hear most weeks is whether it's safe to skip ahead if the first pen caused no side effects at all. If you're weighing that up, it helps to first understand what the doses of Mounjaro actually are and how they're structured, since the schedule exists for tolerability reasons, not arbitrary ones, and skipping steps is not how the licensed titration works. Your prescriber makes that call, with the full picture in front of them, not the other way round.

The six steps, and what actually changes between them

Each of the six strengths corresponds to a four-dose pen. The sequence runs 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg, with roughly four weeks at each level before any increase. You can explore the full Mounjaro overview for broader context about how the medicine is used in the UK.

The gap between steps is not arbitrary. GI effects tend to peak in the days after a dose change and ease off as the body adapts. Moving too quickly doesn't increase effectiveness; it mostly increases the chance of side effects that make treatment harder to sustain.

Not every person reaches 15 mg. Some find a lower dose delivers steady, comfortable progress, and the aim is the lowest dose that works, not the highest one available. There is also nothing unusual about spending longer than four weeks at a given level if tolerability requires it. The prescriber's job is to find the right pace for the individual. If you're curious about how the 5 mg pen fits into this sequence, that page goes into more detail on that specific step.

For those who want to understand the maintenance end of the schedule, the maintenance dose breakdown covers what settling on a long-term strength actually looks like in practice.

When the dose doesn't change, and when it might go back down

There are two situations where the schedule stops moving upward: when a dose is working well, or when a dose is causing side effects that haven't settled. Neither means anything has gone wrong.

If you're responding well at 10 mg, staying there is entirely appropriate, the medicine's licensed target is effective weight management, and the right maintenance dose is the one that achieves that without unnecessary side effects. Jumping to 12.5 mg or 15 mg when things are going well is not a clinical requirement.

Side effects that persist past the initial adjustment period are a reason to discuss the current dose with your prescriber before any increase. In some cases, staying at a lower strength for longer, or pausing a planned increase, is the right move. This is clinical judgement, not a setback. You can find more on tirzepatide dosing decisions or review the dosage guidance for Mounjaro as a reference point.

One detail that surprises people: the dose you end up on long-term may not match what worked for someone else with a similar starting weight. Individual response to tirzepatide varies significantly, and there's no predictive formula. That unpredictability is precisely why clinical oversight throughout the schedule matters.

Private access, NHS access and how a prescriber fits in

Tirzepatide carries a Black Triangle (▼) designation from the MHRA, meaning it's under enhanced safety monitoring, additional reporting applies and prescribers follow that framework closely. NICE's appraisal (TA1026) set out NHS eligibility criteria, though NHS access remains phased and limited in scope for now.

Privately, the eligibility threshold is set by the medicine's licence: adults with a BMI of 30 or above, or 27 and above alongside at least one weight-related health condition. Lower thresholds apply for some ethnic backgrounds under UK guidance. That said, BMI alone doesn't determine whether tirzepatide is appropriate; the prescriber reviews your health history, any medicines you take, and how your previous weight management attempts have gone before making a decision.

At nume, every consultation is reviewed the same day by a GPhC-registered Independent Prescriber. There's no algorithm making the call. If you'd like to understand the full process, the treatment page sets out how a consultation works from start to finish. If you're ready, you can start your free consultation there today.