A Practical Dosage Guide for Tirzepatide

Step 1: The 2.5 mg starting pen and why it exists

Almost every tirzepatide journey begins at 2.5 mg, and patients sometimes wonder whether that dose is doing anything useful. It is, just not in the way you might expect. The first pen's job is adjustment: your gut is encountering a dual GIP and GLP-1 receptor agonist for the first time, and gastric emptying slows noticeably. Nausea, indigestion and loose stools are the most common early complaints, and the 2.5 mg dose keeps those manageable while your body adapts.

You'll inject once a week, on the same day each week if possible, into the abdomen, thigh or upper arm. Rotating the site within those areas matters, injecting into the same spot repeatedly can affect how the medicine is absorbed. The pen itself stores in the fridge at 2–8°C; check the Patient Information Leaflet for the exact out-of-fridge window before any trip away, because the figure is more nuanced than most people assume.

After four weeks at 2.5 mg, your prescriber will review how you've tolerated it. That review is the gateway to the next step. For a deeper look at how the 5 mg pen compares to the starter, that page covers the practical differences in detail.

Step 2: Moving through 5 mg, 7.5 mg and 10 mg

The standard titration increases the dose by 2.5 mg every four weeks, so after the 2.5 mg month, most people move to 5 mg, then 7.5 mg, then 10 mg. Each step is contingent on tolerability. If nausea or gastrointestinal symptoms are still significant, a prescriber may recommend staying at the current dose for an additional four weeks rather than pushing up. That is not a failure; it is the schedule working as designed.

The evidence behind tirzepatide's effectiveness comes from the SURMOUNT clinical programme, which involved thousands of adults and found that higher maintenance doses produced meaningfully greater average weight loss. The SURMOUNT-1 trial, published in the New England Journal of Medicine, reported average body-weight reductions of around 20–21% at the 15 mg dose over 72 weeks, a figure that applies to people who reached that dose and stayed on treatment. Earlier doses contribute to the trajectory, but the therapeutic weight falls mainly at the maintenance level your prescriber settles you on.

If you want dose-specific detail, our tirzepatide 5 mg dosage page covers what changes at that step and what to expect alongside the 10 mg tirzepatide dosage page.

Step 3: 12.5 mg and 15 mg (reaching your maintenance dose

The final two steps) 12.5 mg and 15 mg, are where most of the weight-management benefit is realised. Not everyone reaches 15 mg; some people find they tolerate 10 mg or 12.5 mg better and maintain good progress there. Your prescriber weighs how much weight you've lost, how well you're tolerating the current dose, and whether moving higher is clinically appropriate.

One practical check that takes under a minute: before each injection day, look at the pen in your fridge and confirm the liquid is clear and colourless. If it looks cloudy, discoloured or contains particles, do not use it, contact the pharmacy. It sounds obvious, but it is a step that is easy to skip when the routine becomes automatic.

NICE's appraisal of tirzepatide (TA1026) notes that if less than 5% body weight is lost after six months at the highest tolerated dose, continuing should be clinically reviewed. That threshold is a checkpoint built into the prescribing guidance, not a reason for alarm, many people lose significantly more. Our Mounjaro dosage guide covers the licensed schedule in the broader context of how the medicine is prescribed in the UK, and the full tirzepatide dosage overview on this site adds further detail.

What the dose schedule cannot tell you

A dosage guide like this one can explain the structure of the schedule and the reasoning behind it. What it cannot do is tell you which dose is right for you, whether to stay at your current step or move up, or how to handle a missed injection. Those decisions sit with your prescriber, and rightly so, because they depend on your weight, your health history, any other medicines you take and how your body is actually responding.

Tirzepatide is not licensed for anyone under 18, and it is not recommended during pregnancy, while breastfeeding, or for people actively trying to conceive. Anyone with a history of certain conditions, including pancreatitis, will need a careful prescriber discussion before starting. If you are already on treatment and have questions about your dose, the support team is available seven days a week.

For anyone considering starting, the Mounjaro overview explains how the medicine works and what the treatment pathway looks like. And if you want to understand the full cost picture before committing, the weight-loss treatments page sets out what private treatment includes and how pricing is structured. When you are ready, you can check your eligibility with a free consultation, reviewed the same day by a GPhC-registered prescriber, not a decision tree.