Mounjaro step by step: what actually happens from first injection to maintenance dose

Step 1: the consultation and your starting dose

Before a single pen is dispensed, a prescriber reviews your full clinical picture. At our pharmacy, that review happens the same day you complete your consultation — a real clinician reads your answers, not software. Identity and weight are verified, your medical history is assessed, and the prescriber decides whether Mounjaro is appropriate for you.

If it is, treatment begins at 2.5 mg. Think of this first pen as your system's introduction to the medicine. The dose is deliberately low: nausea and other gastrointestinal effects are most common when tirzepatide is new to the body, and starting gently reduces the chance of them derailing things early. You inject once weekly, typically into the abdomen, thigh or upper arm, rotating sites each time. Storage is in the fridge (2–8°C) until you're ready to use each dose — the Mounjaro use-by and storage rules matter here, so always check the Patient Information Leaflet for the exact out-of-fridge window rather than going by memory.

Most people find the first four weeks manageable. Appetite often begins to shift noticeably even at 2.5 mg, though the primary purpose of this phase is adjustment, not weight change. Stick to the schedule your prescriber has set, and flag anything unexpected via aftercare before deciding anything yourself.

Step 2: titration through the middle doses

After four weeks at 2.5 mg, the schedule typically moves to 5 mg, then 7.5 mg, and so on, each strength held for roughly four weeks before the next increase is considered. The word "considered" matters: titration is not automatic. At each repeat, a prescriber reviews your weight progress, any side effects you've reported, and whether moving up is clinically appropriate. Rushing the ladder doesn't improve results; it usually just increases side effects.

The gastrointestinal effects that are most common with tirzepatide (nausea, loose stools, reduced appetite, occasional reflux) tend to peak shortly after a dose increase and ease within a week or two for most people. The day-by-day experience in the first weeks varies between individuals, but the pattern of "adjustment period then settling" is consistent across the clinical programme. NHS patient guidance on tirzepatide at nhs.uk/medicines/tirzepatide details what to expect at each stage and when symptoms warrant medical attention.

Practically: if you order before midday on a weekday, your next pen arrives the following working day via DPD. That rhythm fits neatly around a regular injection day, many people choose the same day each week, something that doesn't move around (a Sunday evening, say, or a Monday before the school run).

Step 3: reaching and staying at your maintenance dose

The maintenance dose is the highest strength you can tolerate and that your prescriber judges appropriate, anywhere from 5 mg to 15 mg depending on your response and tolerability. Not everyone reaches 15 mg, and that is fine; the trials show meaningful weight reduction at every dose level above the starter. In SURMOUNT-1, involving thousands of adults, average body-weight reduction at 15 mg reached around 20–21% over 72 weeks, as published in the New England Journal of Medicine. Lower maintenance doses produced lower but still clinically significant results.

Once you are stable at your maintenance dose, the clinical re-review continues with every repeat. There are no automatic renewals at our service; each order is individually assessed. NICE's appraisal of tirzepatide (TA1026) sets the benchmark for when to review whether treatment is still working: if weight loss is below 5% after six months at the highest tolerated dose, continuing is not recommended. Your prescriber will have that conversation with you before it becomes an issue.

For context on what this stage costs over time, the Eli Lilly UK price changes page sets out how private treatment pricing has moved and what to expect at different dose levels, useful reading before you reach the higher strengths.

Practical things that support every step

The clinical schedule is the backbone, but a few practical habits make it easier. Inject on the same day each week. Rotate sites consistently to avoid localised discomfort. Keep the pen refrigerated and let it reach room temperature for a few minutes before injecting. If a dose is missed, follow the Patient Information Leaflet guidance, the timing rules depend on how close the missed dose is to the next one, and this is exactly the kind of question our aftercare team handles seven days a week, rather than something to guess at.

Mounjaro works alongside a reduced-calorie diet and increased physical activity, not instead of them. The medicine reduces appetite significantly for most people; using that window to build sustainable habits is the point. Protein intake, hydration and strength activity all matter more than they might seem when appetite is suppressed. Your prescriber or a registered dietitian can advise on specifics.

Any concerns about how the medicine is affecting you (physical or psychological) are worth raising with a clinician rather than leaving. The common concerns people raise about Mounjaro page covers the questions our prescribers hear most often. If you are still weighing up whether this treatment is right for you, check your eligibility with a free consultation and let a prescriber give you a straight answer based on your own picture.