Tirzepatide injection doses: how the Mounjaro schedule works

What are the six tirzepatide injection doses, and why are there so many?

Tirzepatide's UK licence covers six strengths: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. Each comes in a pre-filled KwikPen; a single pen contains four weekly doses. The stepwise structure isn't bureaucracy, it reflects how the medicine works. As a dual GIP and GLP-1 receptor agonist, tirzepatide affects gut-hormone pathways that slow gastric emptying and reduce appetite. Introducing that effect gradually gives the body time to adapt, which matters most for nausea and other gastrointestinal symptoms that tend to be sharpest in the first weeks.

The 2.5 mg injection is the introductory pen. It carries very little weight-loss signal at that concentration; its job is adjustment. Most people stay at that level for roughly four weeks, then move to the 5 mg pen, which is where the body begins to encounter a more meaningful therapeutic effect. From there, steps upward happen in 2.5 mg increments, each typically held for at least four weeks. The clinical aim is the highest dose you tolerate well, not necessarily the highest dose possible. You can read more about Mounjaro as a treatment on our Mounjaro overview page.

It is worth knowing that the 15 mg dose is what produced the headline results in clinical trials. SURMOUNT-1, a 72-week study involving 2,539 adults with obesity, found that participants on 15 mg lost on average around 20–21% of their body weight, as reported in the New England Journal of Medicine. Lower doses produced meaningful but smaller reductions. None of this is guaranteed for any individual, biology varies considerably.

How does dose titration actually work in practice?

Titration means moving up through the doses in a planned sequence. There is no fixed rule that says everyone reaches 15 mg; the prescriber's job is to find the dose at which you're losing weight steadily without side effects that disrupt daily life. Some people do very well at 7.5 mg or 10 mg and stay there. Others work up to the maximum over several months.

The general pattern for someone starting treatment looks like this: four weeks at 2.5 mg, then four weeks at 5 mg, and so on upward. But it is not mechanical. If side effects at a given level are significant, your prescriber may suggest staying at that strength longer before moving up. If you are tolerating a dose well and your progress is good, the conversation about the next step happens at your next clinical review.

Timing matters more than people expect. If your pen runs out during a bank holiday week, or a repeat lands late because you ordered after the Monday midday cut-off, a gap in the schedule is worth flagging to your clinical team rather than doubling up. Detailed guidance on what to do in those situations lives in the Patient Information Leaflet that comes with your pen, and your prescriber is the right person for anything beyond what's in the leaflet. For a closer look at how the dose progression maps onto the full treatment journey, the tirzepatide injection dosage guide covers the practical questions most people ask.

At each repeat, a prescriber reviews your case before any dose increase is confirmed. That review considers whether you've had side effects, what your weight trajectory looks like, and whether continuing at the same or higher dose makes clinical sense. NICE's appraisal of tirzepatide (TA1026) notes that if less than 5% weight loss has occurred after six months at the highest tolerated dose, continuing should be reconsidered, that guidance shapes how clinical reviews are framed.

What side effects are most linked to dose changes?

The side effects most commonly associated with tirzepatide are gastrointestinal: nausea, loose stools, constipation, indigestion, and sometimes vomiting. These tend to be most pronounced in two moments, when starting treatment and whenever the dose increases. That's the main reason the titration schedule moves slowly. Most people find the symptoms settle within a week or two at each new level.

It's also why the 2.5 mg starting pen exists the way it does. Jumping straight to a therapeutic dose would likely mean a rougher first month. The slow-start design is built into the licence, not an optional extra.

Side effects beyond the gut are less common but worth knowing about. Fatigue, headache, dizziness, and injection-site reactions have all been reported. On the question of injection sites: abdomen, thigh, and upper arm are all suitable; rotating the site each week reduces local reactions. The precise injection technique, storage temperatures, and what to do if you miss a dose are covered in full in the medicine's Patient Information Leaflet, those specifics belong with your prescriber and the leaflet, not with general content like this.

If you experience severe, persistent abdominal pain that radiates towards your back, seek medical help promptly. The MHRA issued a Drug Safety Update in January 2026 confirming that acute pancreatitis, while infrequent, is a recognised risk with GLP-1 medicines and warrants urgent attention. You can report any suspected side effect through the MHRA's Yellow Card scheme.

Which dose level might you realistically reach, and who decides?

The honest answer is that no one can tell you in advance. Your starting point, how your digestive system responds to 2.5 mg, and how your weight changes over the first few months all feed into the conversation with your prescriber. Some people reach 15 mg relatively smoothly. Others find a lower dose works well enough that there's no clinical reason to push further.

Eligibility for tirzepatide as a weight-management medicine covers adults with a BMI of 30 or above, or 27 and above alongside at least one weight-related condition such as high blood pressure, type 2 diabetes, high cholesterol, or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. A BMI figure alone doesn't determine treatment; it's the starting point for a fuller clinical assessment. If you want to understand how all the available Mounjaro injection doses compare and what each is intended to achieve, that detail sits alongside the clinical context around the highest strength on the 15 mg injection page.

The private route through a regulated online pharmacy means no referral letter and no waiting list, which suits many people who don't qualify under the current NHS phases or who prefer not to wait. Thinking about costs alongside the clinical picture? Our weight-loss treatments page sets out what's included in the consultation process. If you've been on treatment elsewhere and want to transfer, or if you're starting fresh, the process begins with a free consultation, reviewed the same day by a GPhC-registered prescriber. Our clinical team page describes how clinical oversight works at nume.

Questions that go beyond the general (when to increase, whether to stay at a given dose, what a missed injection means for your schedule) are exactly what the FAQs and your prescriber are there for. Check your eligibility and start your free consultation when you're ready.