Trying to get 3.75mg from your 2.5mg Mounjaro pen? Here's what you need to know

You've been reading about 3.75mg and now you're not sure what to do next

It is a reasonable thing to wonder about. The tirzepatide titration schedule moves in 2.5mg increments (2.5mg, 5mg, 7.5mg and so on) but people sometimes come across references to half-step doses like 3.75mg in online groups or forum threads, where compounded or unlicensed versions circulate. In the UK, the licensed Mounjaro KwikPen is factory pre-set. The 2.5mg pen delivers 2.5mg per click, every time. There is no mechanism to draw a partial dose, and attempting to do so with a pre-filled pen is not clinically appropriate. If you are finding the jump to 5mg uncomfortable, that is a real and common concern (the clinical team at nume regularly hears it) and the right place to raise it is with your prescriber, not a forum. They can advise on strategies like a slower titration or managing side effects at the current dose rather than forcing the next step before you are ready, and reading about how people approach getting 3.75mg Mounjaro can help you understand what those conversations typically involve. The NHS tirzepatide information page also sets out the licensed dose schedule clearly, which is worth reading before making any change.

What the 2.5mg pen is actually designed to do

The starter pen at 2.5mg exists for tolerability, not weight loss. Its job is to let your body adjust to tirzepatide before the dose increases, nausea, stomach discomfort and changes to appetite are most noticeable in the early weeks, and a low starting dose reduces how hard those hit. That is why the licensed schedule stays at 2.5mg for approximately four weeks before the prescriber considers moving things forward. Trying to obtain a non-licensed intermediate dose (including from online sellers marketing unlicensed or compounded tirzepatide) carries significant risk, and if you have wondered whether getting 3.75mg from a 5mg pen is a safe workaround, the short answer is that it is not clinically appropriate with a factory pre-set device. The MHRA has warned repeatedly about counterfeit and unlicensed weight-loss pens sold online, and in 2025 seized roughly 20 million doses of illegally traded weight-loss medicines worth around £45 million, including from the first illicit UK manufacturing site for counterfeit tirzepatide uncovered in Northampton. A pen that claims to deliver a dose not available in the licensed UK range should be treated as a serious red flag. If you are unsure whether a pharmacy is legitimate, check the GPhC pharmacy register before placing any order.

How a dose review works with a properly regulated UK prescriber

If you are already on 2.5mg and wondering whether to move up, the process through a regulated online pharmacy like nume is straightforward. When you request a repeat or a dose change, your case is read by a named GPhC-registered prescriber (a real clinician, not automated software) on the day you submit. They look at how you have been tolerating the current dose, your weight trajectory and any side effects you have reported. They may approve a move to 5mg, advise staying at 2.5mg longer, or suggest something else entirely. What they will not do is sign off a dose that falls outside the licensed UK schedule without a sound clinical reason on record. That protects you. The next licensed step up from 2.5mg is 5mg, and if that transition feels daunting, similar questions come up for people moving from 5mg too. The process is the same: a clinical review first, always.

Starting or continuing Mounjaro through a GPhC-registered pharmacy

Whether you are still at the 2.5mg stage or have been on treatment for several months, accessing Mounjaro through a properly regulated pharmacy follows the same route. You complete a clinical questionnaire. A prescriber reviews it the same day. If treatment is clinically appropriate, your prescription is written and the pen is dispatched, with DPD, the next working day, tracked to your door. If you are new to this and wondering where 2.5mg fits into a longer treatment plan, the starter dose page covers what to expect in those first four weeks. For people who received their initial prescription elsewhere and want to transfer, understanding your GP route first can also be useful context before switching to a private pharmacy. Eligibility for private treatment follows the licensed criteria: adults with a BMI of 30 or above, or 27 or above with at least one weight-related condition such as high blood pressure, type 2 diabetes or high cholesterol. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. A prescriber assesses the full picture, BMI is one input, not the whole answer.