Mounjaro (tirzepatide) is a once-weekly prescription injection for weight management, manufactured by Eli Lilly and licensed in the UK by the MHRA. It works by activating two gut hormone receptors (GLP-1 and GIP) to reduce appetite, support blood sugar regulation, and promote sustained weight loss. In the SURMOUNT-1 clinical trial, participants on the highest dose (15 mg) lost an average of 22.5% of their body weight over 72 weeks. Mounjaro is available on the NHS for a limited group of patients who meet strict eligibility criteria, or via private prescription for adults with a BMI of 30 or above (27 or above with a weight-related health condition), typically within days.
What is Mounjaro and how does it work?
Mounjaro is the UK brand name for tirzepatide, a dual GIP and GLP-1 receptor agonist manufactured by Eli Lilly. It is licensed by the MHRA for both type 2 diabetes and weight management in adults, making it one of two injectable weight management medicines currently available in the UK alongside Wegovy (semaglutide).
Most weight management injections, including Wegovy, work by activating a single receptor: GLP-1. Mounjaro activates two. GLP-1 (glucagon-like peptide-1) reduces appetite, slows how quickly food leaves the stomach, and helps regulate blood sugar. GIP (glucose-dependent insulinotropic polypeptide) works alongside GLP-1 to enhance these effects and may also improve how the body processes fat. Activating both receptors together appears to produce greater weight loss than activating GLP-1 alone, based on clinical trial data.
In practical terms, most people taking Mounjaro notice three things. Appetite reduces, often within the first one to two weeks. Cravings become less frequent and less intense. Portions that previously felt normal start to feel like enough, or more than enough. These effects are not about willpower. They are the result of tirzepatide acting on the same hormonal signals your body uses to regulate hunger.
Mounjaro is administered using a pre-filled KwikPen. Each pen contains four weekly doses (one month's supply). You inject once a week into the stomach, thigh, or upper arm, rotating the injection site each time. The needle is short and thin, and most people report that the injection itself takes a few seconds. No mixing, no measuring, and no refrigeration is needed after the first use (pens can be stored at room temperature for up to 21 days).
What results can you expect from Mounjaro?
In the SURMOUNT-1 trial, the largest clinical trial of tirzepatide for weight management, 2,539 adults with obesity or overweight (without type 2 diabetes) were treated for 72 weeks. Average weight loss was 22.5% at the 15 mg dose, 21.4% at 10 mg, and 16.0% at 5 mg, compared with 2.4% on placebo. Published in the New England Journal of Medicine in July 2022 (NCT04184622).
96% of participants on the 10 mg and 15 mg doses achieved at least 5% weight loss. More than half of those on 15 mg lost 20% or more of their body weight.
For adults with type 2 diabetes, the SURMOUNT-2 trial showed average weight loss of 15.7% at 15 mg and approximately 13.4% at 10 mg over 72 weeks, compared with 3.3% on placebo. Weight loss is typically lower in people with type 2 diabetes, which is consistent across all weight management medicines.
What does this look like in practice?
| Starting weight | 22.5% loss (15 mg) | 16% loss (5 mg) |
|---|---|---|
| 80 kg (12 st 8 lb) | 18 kg lost | 12.8 kg lost |
| 100 kg (15 st 10 lb) | 22.5 kg lost | 16 kg lost |
| 120 kg (18 st 13 lb) | 27 kg lost | 19.2 kg lost |
These figures are based on average trial results. Individual results vary depending on starting weight, dose, diet, physical activity, and adherence to treatment.
Most people notice reduced appetite within the first one to four weeks. Visible weight changes typically become apparent from month two onwards, with the greatest rate of loss occurring during the dose escalation period (months two to six). Weight loss tends to plateau once a stable maintenance dose is reached, which is normal and expected.
Individual responses to Mounjaro vary. Clinical trial averages represent the middle of a range. Some people lose more, some less. Lifestyle factors, including diet and physical activity, play a significant role in outcomes alongside the medication itself.
Mounjaro doses: the full titration schedule
| Dose | Duration | Purpose |
|---|---|---|
| 2.5 mg | Weeks 1–4 | Adjustment phase for tolerability, not weight loss |
| 5 mg | Weeks 5–8 (minimum) | First therapeutic dose |
| 7.5 mg | Weeks 9–12 (minimum) | Escalation if tolerated |
| 10 mg | Weeks 13–16 (minimum) | Mid-range maintenance or continued escalation |
| 12.5 mg | Weeks 17–20 (minimum) | Higher range |
| 15 mg | Week 21 onwards | Maximum dose, maintenance |
The four-week minimum at each dose exists for a reason. Tirzepatide takes time to reach a steady level in the body, and side effects are most common during dose increases. Moving too quickly increases the likelihood of nausea, vomiting, and other gastrointestinal symptoms. Your prescriber will only recommend increasing your dose when you have tolerated the current one for at least four weeks.
Many patients achieve clinically meaningful weight loss at 5 mg or 10 mg without ever reaching 15 mg. There is no clinical requirement to escalate to the maximum dose. Your prescriber will assess your response at each stage and recommend the dose that balances weight loss with tolerability. If you are losing weight steadily and tolerating your current dose well, staying on it is a reasonable and common outcome.
If side effects are significant at a particular dose, staying at a lower dose for an additional four to eight weeks is a standard clinical approach. This does not indicate that treatment is failing. It means your body needs more time to adjust. Dose pausing is built into the prescribing guidelines and your prescriber will advise you if this applies.
Mounjaro side effects: what to expect and how to manage them
Like all prescription medicines, Mounjaro can cause side effects. The most common are gastrointestinal and tend to occur during the first four to eight weeks of treatment and during dose increases. They typically reduce in severity as your body adjusts.
Common side effects (affect more than 1 in 10 people)
Nausea is the most frequently reported side effect, particularly during the first weeks of treatment and each time the dose is increased. Practical management: eat smaller meals more frequently throughout the day, avoid greasy or heavy foods, eat slowly, and stick to bland foods like toast, crackers, and rice when nausea is at its worst. Nausea is usually mild to moderate and temporary.
Diarrhoea can occur at any dose level. Staying well hydrated is important. Reducing fatty and high-fibre foods during acute episodes can help. If diarrhoea is persistent or severe, contact your prescriber.
Constipation is more common in weight management patients than is sometimes expected. Increasing water intake and adding fibre-rich foods to your diet can help. If these adjustments do not resolve it, your prescriber may recommend an over-the-counter treatment.
Vomiting is less common than nausea but can occur during dose escalation. If vomiting persists beyond 24 hours, contact your prescriber. You may need to stay at your current dose for longer before escalating.
Abdominal pain is reported by some patients. Mild discomfort after meals is common during the adjustment period. However, persistent or severe stomach pain, especially pain radiating to the back accompanied by nausea or vomiting, should be reported to your prescriber immediately and may require urgent medical assessment (see safety note below).
Decreased appetite is the intended therapeutic effect of the medication. Occasionally, appetite suppression can feel excessive at higher doses, making it difficult to eat enough to maintain energy levels. If this occurs, speak to your prescriber about adjusting your dose.
Less common but important side effects
Acute pancreatitis is uncommon but serious. Symptoms include severe, persistent stomach pain (often radiating to the back) with nausea and vomiting. If you experience these symptoms, stop taking Mounjaro and seek immediate medical attention.
In January 2026, the MHRA updated its product information for all GLP-1 and dual GLP-1/GIP medicines to highlight a small risk of severe acute pancreatitis, including rare reports of necrotising and fatal pancreatitis. Between 2007 and October 2025, the MHRA received 1,296 Yellow Card reports of pancreatitis across all GLP-1 medicines, of which 19 were fatal and 24 were necrotising. For context, 25.4 million packs of these medicines were dispensed in the UK over five years. Anyone experiencing severe, persistent stomach pain should seek urgent medical attention. Suspected side effects can be reported via the Yellow Card scheme.
Gallstones are a known risk during rapid weight loss, regardless of the method used. Symptoms include pain in the upper right abdomen, particularly after eating fatty food. Report these symptoms to your prescriber.
Fast pulse is uncommon and typically mild. If you notice a persistently fast or irregular heartbeat, contact your prescriber.
Injection site reactions such as redness, swelling, or itching can occur. Rotating injection sites (stomach, thigh, upper arm) reduces the likelihood.
A reassuring note on side effects
Most gastrointestinal side effects are mild to moderate and occur during dose escalation, not throughout the entire course of treatment. The majority of patients who experience nausea during their first month report that it has resolved or reduced significantly by month two or three. Side effects are a common reason for dose pausing, and your prescriber will work with you to find a dose and pace that suits your body.
Who is eligible for Mounjaro in the UK?
Private prescription eligibility
A private prescriber can prescribe Mounjaro for weight management if you meet the following criteria:
- BMI of 30 or above (classified as obesity), or
- BMI of 27 to 29.9 with at least one weight-related comorbidity (type 2 diabetes, hypertension, dyslipidaemia, cardiovascular disease, or obstructive sleep apnoea)
For adults from South Asian, Chinese, Middle Eastern, Black African, or African-Caribbean backgrounds, BMI thresholds are reduced by 2.5 points in line with NICE guidance, reflecting the higher metabolic risk at lower BMI levels in these populations.
Mounjaro is not suitable for everyone. Standard contraindications include pregnancy, breastfeeding, a personal or family history of medullary thyroid carcinoma, a diagnosis of multiple endocrine neoplasia type 2 (MEN2), and a history of acute pancreatitis. Your prescriber will assess your full medical history before recommending treatment.
NHS eligibility
NHS access to Mounjaro for weight management is being rolled out in phases. Eligibility is strictly defined by NHS England's interim commissioning guidance, which prioritises patients with the highest clinical need.
| NHS cohort | Start date | Criteria |
|---|---|---|
| Cohort 1 | June 2025 | BMI 40+ (37.5+ for eligible ethnic groups) AND 4 of 5 qualifying conditions |
| Cohort 2 | June 2026 | BMI 35–39.9 (32.5+ for eligible ethnic groups) AND 4 of 5 qualifying conditions |
| Cohort 3 | April 2027 | BMI 40+ (37.5+ for eligible ethnic groups) AND 3 of 5 qualifying conditions |
The five qualifying conditions are: type 2 diabetes, hypertension, dyslipidaemia, cardiovascular disease, and obstructive sleep apnoea. NHS prescribing also requires participation in a mandatory wraparound care programme that includes dietary, physical activity, and behavioural support.
From 1 April 2026, NHS prescribing of tirzepatide for obesity sits within the GP Quality and Outcomes Framework (QOF) contract. Participation is optional at practice level, which means availability varies between areas and GP surgeries. Meeting the eligibility criteria does not guarantee access.
The practical reality: the vast majority of people who would benefit from Mounjaro, including those with a BMI of 30 to 39 or fewer than four comorbidities, will need a private prescription in 2026 and likely into 2027. The NHS route is currently reserved for the highest-need patients and full rollout is expected to take up to 12 years.
How to get Mounjaro in the UK
NHS route
Speak to your GP about whether you meet the current cohort eligibility criteria. If eligible, your GP may prescribe directly (if their practice has opted into the QOF pathway) or refer you to a specialist weight management service. Waiting times for specialist services vary by area, with some patients waiting 6 to 12 months or longer. If prescribed on the NHS, you pay the standard prescription charge (currently £9.90 per item in England, free in Scotland, Wales, and Northern Ireland).
Private prescription route
Complete an online health assessment, typically taking 5 to 10 minutes. A regulated prescriber reviews your medical information and assesses your clinical suitability. If clinically appropriate, a prescription is issued. Your medication is dispensed by a GPhC-registered pharmacy and delivered, usually within 2 to 3 working days, via tracked cold-chain delivery.
When choosing a private provider, verify that prescribers are registered with the GMC, GPhC, or NMC, and that the dispensing pharmacy is GPhC-registered. You can check a pharmacy's registration status on the GPhC register.
A note on safety: Mounjaro sold without a prescription, from unregulated sellers, or without a prior clinical assessment is not safe. Counterfeit tirzepatide has been identified in the UK, and the MHRA has confirmed seizures of falsified products. Only purchase from a regulated UK pharmacy with a valid prescription from a registered prescriber. If you suspect a non-compliant provider, report it via the MHRA reporting page.
Mounjaro cost in the UK
Private Mounjaro treatment in the UK currently costs between approximately £120 and £220 per month for the 2.5 mg starter dose, rising to £170 to £340 per month at the 15 mg maintenance dose, depending on the provider and what is included. Prices vary significantly because Eli Lilly raised UK wholesale prices in September 2025, and different pharmacies have absorbed or passed on that increase to varying degrees.
When comparing providers, always look at the total monthly cost, not the headline medication price. Some providers charge separately for the clinical assessment, prescribing fees, needles, sharps bin, and delivery. These extras can add £30 to £50 per month on top of the quoted price. Others include everything in a single figure.
For patients planning 12 months or more of treatment (which most people will need for sustained results), an annual membership model can reduce total service fees compared to paying per order. Over a year, the difference in service fees alone can amount to a meaningful saving.
For a detailed breakdown of all doses, a comparison of NHS, pay-as-you-go, and membership pricing, and guidance on what to check before choosing a provider, see How much does medical weight loss cost in the UK? 2026 price guide.
Mounjaro vs Wegovy: which is right for you?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are licensed in the UK for weight management in adults. The main difference is their mechanism: Mounjaro activates two receptors (GLP-1 and GIP), while Wegovy activates one (GLP-1 only).
Clinical trial data for each drug comes from separate studies with different populations and durations, so direct comparison should be interpreted with care. In the SURMOUNT-1 trial (72 weeks, non-diabetic adults), tirzepatide 15 mg produced average weight loss of 22.5%. In the STEP-1 trial (68 weeks, non-diabetic adults), semaglutide 2.4 mg produced average weight loss of 14.9%. Longer-term data from STEP-5 showed semaglutide maintained average weight loss of 15.2% over 104 weeks. Individual responses to either medicine vary.
Following Eli Lilly's September 2025 wholesale price increase, Wegovy is typically £50 to £100 per month cheaper than Mounjaro at comparable dose stages. For some patients, the lower cost of Wegovy makes it the better long-term option. For others, the potentially greater weight loss with Mounjaro justifies the higher price. Your prescriber can help you weigh the clinical and practical factors for your situation.
For a full clinical and cost comparison of both medicines, see What is Wegovy? What is Mounjaro? A 2026 UK guide.
Frequently asked questions
What is Mounjaro and what is it used for in the UK?
Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine manufactured by Eli Lilly. It is licensed in the UK by the MHRA for both type 2 diabetes and weight management in adults. For weight management, it is prescribed alongside dietary changes and increased physical activity for adults with a BMI of 30 or above, or 27 or above with at least one weight-related health condition. It works by activating two gut hormone receptors (GLP-1 and GIP) to reduce appetite and support sustained weight loss.
How does Mounjaro work differently from Wegovy?
Mounjaro activates two hormone receptors: GLP-1 and GIP. Wegovy activates GLP-1 only. Both reduce appetite and slow gastric emptying, but the dual action of Mounjaro may account for the greater average weight loss seen in clinical trials. They are separate medicines with different dosing schedules and titration pathways, and individual responses to each can vary.
How much weight can I expect to lose on Mounjaro?
In the SURMOUNT-1 clinical trial, average weight loss over 72 weeks was 22.5% at the 15 mg dose and 16.0% at 5 mg. For an adult weighing 100 kg, that would mean losing approximately 22.5 kg at the highest dose. Individual results depend on starting weight, the dose you reach, diet, physical activity, and how long you continue treatment. Your prescriber will set realistic expectations based on your personal circumstances.
What are the most common side effects of Mounjaro?
The most common side effects are gastrointestinal: nausea, diarrhoea, constipation, vomiting, and abdominal discomfort. These typically occur during the first weeks of treatment and when the dose is increased, and they tend to reduce over time. Most patients who experience nausea during month one report significant improvement by month two or three. In January 2026, the MHRA also highlighted a small risk of severe acute pancreatitis with GLP-1 medicines. Severe, persistent stomach pain should be reported immediately.
Am I eligible for Mounjaro in the UK?
For a private prescription, you typically need a BMI of 30 or above, or a BMI of 27 or above with at least one weight-related health condition such as type 2 diabetes, hypertension, or obstructive sleep apnoea. BMI thresholds are reduced by 2.5 points for adults from South Asian, Chinese, Middle Eastern, Black African, or African-Caribbean backgrounds. A prescriber will assess your full medical history before recommending treatment.
Can I get Mounjaro on the NHS?
NHS access to Mounjaro for weight management is currently limited to patients who meet strict criteria. In 2025/26, eligibility requires a BMI of 40 or above and at least four of five qualifying comorbidities. These criteria are expected to broaden gradually, with Cohort 2 (BMI 35+, four comorbidities) opening from June 2026. Full rollout is expected to take up to 12 years. GP practice participation is optional, so availability varies by area.
How much does Mounjaro cost in the UK?
Private Mounjaro costs between approximately £120 and £220 per month for the 2.5 mg starter dose, depending on the provider and what is included. Higher maintenance doses (10 mg to 15 mg) cost £170 to £340 per month. Always check whether the quoted price includes the clinical assessment, prescribing fee, needles, sharps bin, and delivery. Annual membership models can reduce total service fees for patients on long-term treatment.
How long does it take for Mounjaro to work?
Most people notice reduced appetite within the first one to four weeks. The 2.5 mg starting dose is an adjustment phase for tolerability rather than weight loss. Visible weight changes typically become apparent from month two onwards, as the dose increases into the therapeutic range (5 mg and above). The greatest rate of loss usually occurs during the dose escalation period. Your prescriber will review your progress at regular intervals.
Foundry is a CQC-regulated UK telehealth service. Our clinical team assesses your eligibility, issues your prescription through GMC-registered prescribers, and dispatches your medication from a GPhC-registered pharmacy, typically within 2 to 3 working days. Pricing covers your clinical assessment, prescribing, medication, needles, and sharps bin. Shipping is charged separately at checkout.
Check your eligibilityTreatment is subject to prescriber approval and clinical suitability. Results vary between individuals. Mounjaro is a prescription-only medicine. Prices referenced in this guide are approximate market ranges as of April 2026 and may change. Foundry pricing is available at myfoundry.co.uk. Shipping is not included in medication pricing.