Mounjaro 15mg Injection

Mounjaro 15mg is the highest available dose of tirzepatide, reserved for patients who have gradually increased through all previous strengths (2.5mg → 5mg → 7.5mg → 10mg → 12.5mg) with good tolerance. It is designed to:

• Maximise appetite control and support continued weight loss when earlier doses plateau.
• Improve insulin sensitivity and stabilise blood glucose – this is particularly important in people with type 2 diabetes¹, but is beneficial for anyone on their weight loss journey.
• Support metabolic health by acting on gut and brain receptors that regulate hunger, satiety, and energy use².

You’ll usually be considered for 15mg if:

• You’ve been on 12.5mg for at least 4 weeks
• Your side effects are mild and manageable
• Your weight loss has slowed or plateaued
• You and your clinician agree there’s benefit in moving up

The Mounjaro 15mg injection is the maximum dose, so both the benefits and challenges may feel more noticeable.

Potential benefits include:

• Stronger and longer-lasting appetite suppression.
• Reduced cravings and emotional eating.
• More consistent weight loss.
• Improved blood sugar control and metabolic markers.

Possible side effects may include:

• Nausea, bloating, or mild constipation (often temporary).
• Fatigue during the first 1-2 weeks after dose increase.
• Slower digestion – smaller, protein-rich meals can help.

Seek urgent care for severe, persistent upper abdominal pain, and contact your clinician about ongoing nausea, vomiting, or signs of dehydration.

A Mounjaro 15mg pen costs £329 for 4 weeks, which works out to around £10.97 per day.

When you order through Medicspot, your treatment includes:

• Ongoing clinical support from UK-registered prescribers who monitor your progress and adjust your plan where needed.
• Access to health coaching, helping you build sustainable habits around food, activity, and mindset.
• 12 months of free aftercare once you finish your programme – including check-ins, resources, and personalised maintenance guidance to reduce the risk of weight regain.

At 15mg, tirzepatide works at full capacity across key pathways:

• GLP-1 and GIP signalling is enhanced, reducing appetite signals from the brain.
• Insulin release improves, helping your body use glucose more efficiently.
• Your body becomes more efficient at using stored fat for energy, especially around the belly and internal organs.

Even if weight loss slows, these internal changes support long-term cardiovascular and metabolic health, including improved cholesterol and blood pressure³.

“I didn’t lose weight for 3 weeks at 12.5mg, but after one week on 15mg the scale started moving again.”

 

“The nausea was rough at first, but then I felt completely normal, just full on tiny meals.”

You may be ready for 15mg if:

• You’ve tolerated 12.5mg for at least four weeks.
• Side effects are mild or improving.
• Weight loss has plateaued and you’re still experiencing hunger or cravings.

You may want to wait or step down to 12.5mg:

• Side effects are persistent or interfering with daily life.
• You’ve experienced rapid weight loss and want to stabilise.
• You’ve reached your goal weight and want to maintain.

Because the 15mg injection is powerful, there are a few important don’ts:

• Don’t ignore ongoing or severe nausea, bloating or fatigue
• Don’t assume more is always better, some people manage best at lower doses
• Don’t skip meals to “boost” your results – this often backfires
• Don’t share your pen or use someone else’s medication even if the dose is the same

Research shows that some people regain weight after stopping GLP-1 medication if lifestyle habits aren’t supported⁴. This happens because appetite and hunger hormones can return to pre-treatment levels once the medication is withdrawn.

That’s why ongoing support after your treatment matters just as much as the medication itself.

Medicspot’s 12-month free aftercare

To help members maintain their progress, Medicspot offers 12 months of free aftercare once you complete your Mounjaro programme. This includes:

• Regular check-ins with a health coach focused on nutrition, mindset, and behaviour change.
• Access to educational resources, including our “Life After GLP-1s” course.
• Ongoing support from other members on WhatsApp.

Our goal is to help you keep the weight off sustainably, not just while you’re on medication, but long after.

What the guidelines say

NICE recommends that pharmacological treatment is delivered with ongoing structured lifestyle and behavioural support within specialist services to help maintain weight loss and reduce regain⁵.

This means ongoing coaching and behaviour change support is clinical best practice in the UK.

Reaching the 15mg Mounjaro dose is an important milestone – it means you’ve given your body time to adapt and are now benefiting from the medication’s full effect.

At this stage, many people notice steadier energy, reduced cravings, and improved confidence in maintaining healthier habits.

Continue checking in with your clinician regularly, listen to your body, and celebrate your progress. Every step, from 2.5mg to 15mg, is part of building a more sustainable, healthier future.

Dr Jackir Hussain is a GP with over 14 years of experience, having earned his medical degree from the University of Manchester. He has worked across a wide range of primary care settings, including NHS surgeries, unscheduled care services, homeless shelters, and telemedicine. Dr Hussain is passionate about delivering accessible, patient-centred care and helping individuals take practical steps toward improving their health. In his role at Medicspot, he brings a wealth of frontline experience and a calm, compassionate approach to supporting patients on their weight management journey.

Dr Abby Hyams grew up in Manchester and completed her medical training in Bristol. She has been a GP for 19 years, spending many of those as a partner in an NHS practice in Hemel Hempstead. Dr Hyams loves being a GP because of the wide spectrum of people she encounters every day and the opportunity to make a meaningful difference in their lives. She has a particular passion for supporting patients with weight loss and promoting positive behaviour change, helping individuals build sustainable habits that improve their long-term health and wellbeing.

¹ Frías J P, Davies M J, Rosenstock J et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. The New England Journal of Medicine. Last accessed November 2025. [https://www.nejm.org/doi/full/10.1056/NEJMoa2107519]

² Rosenstock J et al. Dual GIP and GLP-1 receptor agonist tirzepatide improves glycaemic control and body weight in type 2 diabetes (SURPASS-1). Lancet. Last accessed November 2025. [https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01324-6/abstract]

³ Sattar N., McGuire D.K., Pavo I., et al. Tirzepatide cardiovascular event risk assessment: a pre-specified meta-analysis. Nature Medicine. Last accessed November 2025. [https://www.nature.com/articles/s41591-022-01707-4]

⁴ Berg S, Stickle H, Rose SJ, Nemec EC. Discontinuing glucagon-like peptide-1 receptor agonists and body habitus: A systematic review and meta-analysis. Obesity Reviews. Last accessed November 2025. [https://onlinelibrary.wiley.com/doi/10.1111/obr.13929]

⁵ National Institute for Health and Care Excellence (NICE). People need support to keep weight off after treatment ends. News article (2025). Last accessed November 2025. [https://www.nice.org.uk/news/articles/people-need-support-to-keep-weight-off-after-treatment-ends]

Eli Lilly and Company Ltd. “Mounjaro® KwikPen 15 mg solution for injection in pre-filled pen – Summary of Product Characteristics (SmPC).” Electronic Medicines Compendium (eMC). Last accessed November 2025. [https://www.medicines.org.uk/emc/product/15486/smpc]

Diabetes UK. Mounjaro (tirzepatide) – uses, how it works and side effects. Last accessed November 2025. [https://www.diabetes.org.uk/about-diabetes/looking-after-diabetes/treatments/tablets-and-medication/glp-1/mounjaro]

This article is for general information only and should not be used for the diagnosis or treatment of medical conditions. Medic Spot Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. In the event of an emergency, please call 999 for immediate assistance.

There is no guarantee of a specific weight loss medication being prescribed. Clinicians will review your online questionnaire and will recommend the most appropriate weight loss treatments for you based on your answers. In some cases the clinicians may contact you for additional information. See our Terms of Service for more information.