There is no single guaranteed figure, but a realistic guide for most UK users is roughly 1–2% of body weight per month once you have moved beyond the low starter dose, with faster early loss for some and slower loss for others. In the SURMOUNT-1 trial, participants on the 15mg dose lost on average 22.5% of body weight over 72 weeks (about 16–17 months), alongside lifestyle support — which averages out to a little over 1% per month across the whole study. Individual results vary; not everyone reaches this.
What "average per month" really means
Monthly weight loss on Mounjaro (tirzepatide) is rarely a steady, identical number each month. Loss tends to be quicker in the first few months and then gradually flattens as your body adjusts and as you approach a new, lower stable weight.
Mounjaro works by activating two gut-hormone receptors — GLP-1 and GIP — at the same time. This reduces appetite and slows how quickly your stomach empties, so you feel full sooner and for longer, which naturally lowers how much you eat.
Because appetite reduction builds as your dose increases, the early weeks on the 2.5mg starter dose are designed mainly to help your body tolerate the medicine — not to deliver dramatic loss. Meaningful monthly change usually becomes clearer once you have titrated up.
The dose ladder and why it matters for monthly loss
Mounjaro is a weekly self-injection that is stepped up slowly to help manage side effects. The licensed path is:
- 2.5mg (starter — tolerance, not primarily weight loss)
- 5mg
- 7.5mg
- 10mg
- 12.5mg
- 15mg (maximum licensed dose)
Most people stay on each step for at least four weeks before moving up, if it is clinically appropriate. This means it can take several months to reach a higher dose, and your fastest average monthly loss often comes during the middle of this journey rather than right at the start.
A prescriber decides each step based on how you are responding and tolerating the medicine — there is no benefit to rushing, and higher doses are not automatically prescribed for everyone.
A realistic month-by-month picture
The figures below are illustrative ranges to set expectations, not promises. Your actual loss depends on your starting weight, dose, diet, activity, sleep, other medical conditions and how your body responds.
| Stage | Typical pattern |
|---|---|
| Month 1 (2.5mg) | Small loss or mainly appetite/adjustment changes; some water-weight shift |
| Months 2–4 (5–7.5mg) | Often the most noticeable monthly loss as appetite reduction builds |
| Months 5–9 (10–12.5mg) | Continued steady loss, usually gradually slowing |
| Months 10+ (up to 15mg) | Slower loss approaching a new stable weight |
A helpful rule of thumb: losing around 0.5–1kg per week during the more active phases is common for many people, but slower loss is still clinically worthwhile and does not mean the medicine is failing.
Why your results may differ from the trial average
Trial averages combine thousands of people, so your personal figure can sit above or below them. Factors that influence monthly loss include:
- Starting weight — a higher starting weight often means larger early loss in kilograms.
- Diet and protein intake — the medicine reduces appetite, but what you eat still shapes results.
- Activity and muscle — resistance exercise helps protect muscle as you lose weight.
- Dose and how long you have been on it — loss is usually not linear.
- Sleep, stress and other medications — all can affect appetite and weight.
The trial results were achieved alongside lifestyle support — the medicine is a tool that works best with sustainable eating and movement habits, not a replacement for them.
What if weight loss stalls?
Plateaus are normal and expected. Your body adapts to a lower weight, and loss naturally slows as you approach a new balance point.
If your loss stalls, it does not automatically mean you need a higher dose. A prescriber may review your food intake, activity, dose timing and overall progress before making any change. Sometimes staying on your current dose longer, or focusing on protein and strength work, is the right step.
You can discuss any concerns through ongoing prescriber support if you are treated with us — get in touch via our contact page.
How Mounjaro compares to other options
Mounjaro is one of several treatments. Others include the Wegovy injection (semaglutide) and the once-daily Wegovy Tablet (oral semaglutide). Each has its own trial data, dosing and monthly expectations, and none should be presented as automatically "best" — the right choice depends on your health, preferences and a prescriber's assessment.
You can compare the full range on our treatments overview or read more about injectable options on our weight-loss injections page.
Side effects to be aware of
Because appetite and digestion changes drive the results, gastrointestinal side effects are the most common. Side effects affecting more than 1 in 10 people include nausea, diarrhoea, constipation, vomiting, decreased appetite and fatigue.
Rare but serious risks include severe allergic reaction, acute pancreatitis, severe hypoglycaemia (low blood sugar), severe gastrointestinal disease and worsening diabetic retinopathy. Seek medical help if you experience severe or persistent symptoms.
You can report any suspected side effect to the MHRA Yellow Card scheme at https://yellowcard.mhra.gov.uk/.
Who Mounjaro is for
Mounjaro is a Prescription-Only Medicine available only after a clinical consultation with a GPhC-registered prescriber. It is generally considered for adults aged 18+ with a BMI of 30 or above, or a BMI of 27–30 with a weight-related condition such as type 2 diabetes, high blood pressure or sleep apnoea.
It is not suitable for everyone — including during pregnancy or breastfeeding, with type 1 diabetes, a personal or family history of medullary thyroid cancer or MEN2, a history of pancreatitis, severe gastrointestinal disease, an active eating disorder, or severe liver or kidney impairment. A treatment is prescribed only if it is clinically appropriate for you.
If you would like to know whether it is a suitable option, you can begin a free eligibility check with our online consultation. Learn more about how our regulated UK pharmacy works on our about page.
This article is for information only and is not a substitute for personalised medical advice. Weight-loss medicines are prescription-only, are not suitable for everyone, and are prescribed only after a clinical consultation with a GPhC-registered prescriber. Individual results vary. Always speak to a UK-registered pharmacist or doctor before starting or changing any prescription medication.
