Both gastric sleeve surgery and newer medications like Mounjaro (tirzepatide) have revolutionised obesity and type 2 diabetes management. Individually, they can lead to dramatic weight loss and improved metabolic health. But what happens when the two are combined? Can someone who has already had a gastric sleeve benefit from starting Mounjaro?
This article explores current evidence and expert guidance to help you understand whether Mounjaro may be a safe and effective option after bariatric surgery.
What Is Mounjaro and How Does It Work?
Mounjaro is a once-weekly injectable medication that activates two hormones involved in glucose and appetite regulation—GLP-1 and GIP. It was originally developed for type 2 diabetes but has also shown remarkable weight loss effects, even in people without diabetes.
In the SURMOUNT-1 trial, published in The New England Journal of Medicine (2022), people lost up to 22.5% of their body weight over 72 weeks. These results rival or even exceed what is typically seen after bariatric surgery.
Mounjaro is currently recommended by NICE as a weight loss medication, even for individuals without type 2 diabetes. According to NICE guidelines, it can be prescribed for adults with a BMI of 35 or above who have at least one obesity-related health condition (such as hypertension, sleep apnoea, or joint problems). While NHS access is subject to specific criteria, Mounjaro is also available privately, where eligibility is assessed on a case-by-case basis through a thorough medical review to ensure the treatment is appropriate and safe.
How Does a Gastric Sleeve Work?
The sleeve gastrectomy is a surgical procedure that removes around 80% of the stomach. This reduces food intake and alters hormone levels, including ghrelin, the hunger hormone. Most people lose 25–30% of their body weight within the first year or two.
However, for some individuals, weight loss may plateau or even reverse in the years following sleeve gastrectomy. This can happen for several reasons, including stretching of the stomach pouch, hormonal changes such as increased ghrelin levels, a return to old eating habits, reduced physical activity, and lack of long-term follow-up care. A study estimated that 13% to 30% of patients experience long-term weight regain after surgery. The research also linked greater weight regain to larger remaining stomach volume, higher fat intake, and in some cases, psychological factors such as anxiety. In these situations, a medication like Mounjaro may be considered to help manage appetite and support continued weight management—but only under the guidance of a GP or bariatric specialist.
Is It Safe to Take Mounjaro After Gastric Sleeve?
Yes, in many cases, Mounjaro can be used safely after gastric sleeve surgery under medical supervision. There are no formal contraindications to using Mounjaro (tirzepatide) post-surgery, and its mechanism of action complements the effects of surgery by targeting appetite regulation and improving insulin sensitivity through hormonal pathways.
Every patient is different, and a thorough medical assessment is essential to determine whether the treatment is appropriate. Research shows that bariatric surgery naturally increases GLP-1 levels—a gut hormone that plays a key role in appetite control and blood sugar regulation. This has led to growing interest in using GLP-1–based medications, such as Mounjaro, to enhance or sustain these benefits in cases where patients experience weight regain or have ongoing type 2 diabetes after surgery. While clinical experience is promising, the use of Mounjaro post-surgery should always be guided by a GP or bariatric specialist to ensure safety and effectiveness.
What Are the Risks and Considerations?
The most common side effects of Mounjaro include nausea, vomiting, diarrhoea, and constipation. While manageable for many, these issues can be more problematic after bariatric surgery, when the stomach is smaller and digestion is already altered. Patients are more prone to dehydration and food intolerance post-surgery, and Mounjaro may exacerbate these symptoms.
Another major concern is nutrient deficiency. After a gastric sleeve, patients are often at risk of low levels of vitamin B12, iron, calcium, and folate. Since Mounjaro suppresses appetite further, there’s a risk of inadequate intake unless patients are carefully monitored and take the right supplements.
In addition, people who have had bariatric surgery may respond more sensitively to medications. Most specialists recommend starting Mounjaro at the lowest possible dose and increasing gradually while closely observing for side effects.
What About Access and Prescribing in the UK?
Mounjaro is now recommended by NICE for weight management, including for individuals without type 2 diabetes, provided certain criteria are met. It is approved for adults with a BMI of 35 or above who have at least one obesity-related health condition.
Private obesity clinics in the UK also offer Mounjaro to eligible individuals, including those who have previously undergone bariatric surgery and are struggling with weight regain. Accessing treatment privately involves a thorough medical assessment, ongoing clinical monitoring, and can be a significant financial commitment.
If you’re considering Mounjaro as part of your post-surgery weight management journey, our sister company, Semapen (part of Phoenix Health), offers a dedicated Mounjaro programme designed to provide medical oversight and tailored support. Feel free to get in touch with us to find out more or to discuss your individual suitability.
For those interested in research, clinical trials are also underway in the UK to evaluate tirzepatide (Mounjaro) across different patient groups, including individuals with a history of bariatric surgery. You can explore current opportunities through Be Part of Research, the NHS-backed clinical trial platform.
When Might Mounjaro Be Helpful After Surgery?
Under current UK guidelines, Mounjaro is approved for adults with type 2 diabetes and a BMI of 35 or above, or in certain cases for those with a lower BMI if they have additional obesity-related health risks. For patients who have undergone bariatric surgery, Mounjaro is generally considered only if type 2 diabetes remains an issue or in exceptional cases of significant weight regain—and always following a full medical review. If you are exploring this option privately, your GP and bariatric specialist must assess whether Mounjaro is suitable for your specific health profile and surgical history.
However, it may not be suitable for those who:
- Experience regular nausea or vomiting post-surgery
- Have poor tolerance to medication
- Are pregnant or planning pregnancy
- Lack access to ongoing clinical monitoring
As with any medical treatment, the decision to use Mounjaro after bariatric surgery should be made in close consultation with your GP, bariatric specialist, and prescribing clinician, with careful consideration of your individual medical history and nutritional status.
The use of Mounjaro following gastric sleeve surgery is an emerging area of interest in obesity and metabolic health management. At present, there is no large-scale evidence proving the safety or effectiveness of Mounjaro specifically in post-bariatric patients. However, early clinical experience and data from similar medications such as wegovy (semaglutide) and liraglutide suggest that GLP-1–based treatments may be beneficial for some individuals after bariatric surgery, particularly those facing weight regain or ongoing metabolic challenges.
Mounjaro, being a newer and more potent dual-agonist medication, is currently being explored in this context. Given the altered anatomy after gastric sleeve surgery and the potential for increased gastrointestinal side effects, extra caution and ongoing monitoring are essential.
However, this is not a treatment to approach casually. It requires a tailored plan, nutritional support, and regular follow-up to ensure safety and long-term success. As with all aspects of obesity care, the best results come from combining medication, lifestyle changes, and specialist guidance.
Medically Reviewed by Mr. Qutayba Almerie, MD, MSc, FRCS
Consultant Upper GI & Bariatric Surgeon, Medical Director at Phoenix Health.
References:
Lauti M, Kularatna M, Hill AG, MacCormick AD. Defining Weight Regain After Sleeve Gastrectomy: A Systematic Review. Obes Surg. 2016;26(4):923–929. https://doi.org/10.1007/s11695-016-2225-3.
Alvarez V et al. Mechanisms of long-term weight regain in patients undergoing sleeve gastrectomy. Nutrition. 2016. https://doi.org/10.1016/j.nut.2015.08.023
Kim M et al. Prediction of 5-Year Weight Loss and Weight Regain According to Early Weight Loss after Sleeve Gastrectomy. Obes Surg. 2023;33:1366–1372. https://doi.org/10.1007/s11695-023-06536-1
Hutch CR, Sandoval D. The Role of GLP-1 in the Metabolic Success of Bariatric Surgery. Endocrinology. 2017. https://doi.org/10.1210/en.2017-00564
National Institute for Health and Care Excellence (NICE). Tirzepatide for Treating Obesity and Overweight. NICE Technology Appraisal Guidance [TA1026]. Published 13 June 2024. Available at: https://www.nice.org.uk/guidance/ta1026
