Case Presentation
A 34-year-old female was admitted to the medical admissions unit via the emergency department (ED) feeling generally unwell, lethargic, and light-headed with gastrointestinal (GI) symptoms of severe nausea and persistent watery diarrhoea (> 10 episodes per day) of 2 weeks’ duration. She was unable to tolerate anything by mouth and had vomited several times the day before. There was no report of having fever, dyspepsia, bloating, abdominal pain, blood or mucous in vomitus or stool. She did not have coryzal or urinary symptoms. Neither did she have recent travel history.
The patient presented once previously to the ED following an episode of fainting two weeks ago. She recalled transient loss of consciousness lasting less than a minute, preceded by light-headedness. However, there was no evidence of a seizure, post-ictal confusion, disorientation or neurological deficit. She was treated with supportive measures and was discharged the same day with a diagnosis of vasovagal syncope secondary to dehydration.
Prior to these two admissions, the patient was generally fit and well. The only reported past medical history including medication history was that of depression for which she was taking sertraline 100 mg once a day. She does not smoke and rarely drinks alcohol. She is a mother of 3 children and none of her family members at home had similar symptoms.
On examination, the patient had a GCS of 15/15 but appeared lethargic. She was afebrile but was found to be hypotensive (BP 108/74 mmHg), tachycardic (HR 107 beats/min), and clinically dehydrated. Cardiorespiratory examinations were unremarkable, and her abdomen was soft and non-tender, with good bowel sounds.
On further probing, the patient admitted to self-medicating with Tirzepatide for weight loss, which she reported to have stopped taking 4 weeks before the current admission. She had sourced the injections from a private supplier which she did not wish to disclose. She had administered the injections once weekly for 16 weeks before complete discontinuation. Her BMI was 30.4 kg/m2 before initiation. There was no history of diabetes or other cardiovascular risk factors. The initial dose was 2.5 mg per week for 4 weeks, which was gradually titrated to 5 mg weekly. However, due to significant and rapid weight loss and diarrhoea, the patient reduced the dose back to 2.5 mg in the last 2 weeks before completely stopping the medication. Despite this, the patient reported continued weight loss along with persistent diarrhoea two weeks after discontinuation of Tirzepatide. She lost 22 kg in total in 16 weeks.
Investigation results including full blood count, urea and electrolytes, calcium, magnesium, liver function, thyroid function, lipase, and C-reactive protein all were within normal ranges. Stool culture was also negative. The patient showed significant clinical improvement with supportive treatment of IV hydration and anti-emetics.
| Table 1. Investigation Results Investigation | Results During Admission | Reference Ranges |
| Haemoglobin | 148 | 115 – 165 g/ L |
| White Cell Count | 7.48 | 3.6 – 11.0 x 109/L |
| Platelet Count | 227 | 140 – 400 x109/L |
| Sodium | 136 | 133–146 mmol/L |
| Potassium | 4.2 | 3.5–5.3 mmol/L |
| Urea | 3.8 | 2.5 – 7.8 mmol/L |
| Creatinine | 61 | 45–84 μmol/ L |
| eGFR | >90 | >90 |
| C-Reactive Protein | <1.0 | < 5mg/L |
| Total Alkaline Phosphatase | 47 | 30–130 U/L |
| ALT | 7 | <33 U/L |
| Total Bilirubin | 14 | <21 μmol/L |
| Phosphate | 1.04 | 0.74 – 1.4 mmol/L |
| Adjusted Calcium | 2.31 | 2.2-2.6 mmol/L |
| Magnesium | 0.75 | 0.7–1.0 mmol/L |
| Lipase | 27 | <67 U/L |
Before discharge, the appropriate indication for the use of Tirzepatide was explained to the patient and she was counselled about the adverse effects as well as the need for appropriate monitoring of weight, dose adjustment, and side-effects by a health care professional. Safety netting advice was also given to return to ED if she feels unwell again, develops syncopal episode, abdominal pain, or worsening of GI symptoms.
Discussion
Tirzepatide, commonly known as Mounjaro, is the very first GLP-1 (glucagon-like peptide-1) and GIP (gastrointestinal peptide) receptor co-agonist approved for use in weight management in overweight and obese patients. In a meta-analysis of 12 randomised controlled trials by Cai et al, Tirzepatide could significantly reduce the body weight, BMI, and waist circumference in patients compared to GLP-1 receptor agonists, placebo, and insulin groups1. Further subgroup analysis showed a dose-dependent therapeutic effect for Tirzepatide. The incidence of GI adverse reactions was significantly higher in the Tirzepatide group compared to placebo and insulin groups but only slightly higher to the GLP-1 receptor agonists group1. The hypoglycaemic risk of Tirzepatide was also slightly higher to that of the placebo and GLP-1 receptor agonists group but significantly lower than that of the insulin group1.
In the UK, Tirzepatide is recommended as an option for weight management as an adjunct to a reduced calorie diet and increased physical activity in adults only if they have an initial BMI of at least 35 kg/m2 and at least 1 weight-related comorbidity such as hypertension, dyslipidaemia, cardiovascular disease, obstructive sleep apnoea, pre-diabetes, or type 2 diabetes mellitus 2.
More recently, there has been a growing concern among health care professionals due to easy accessibility of Tirzepatide by the public without medical advice and increased cases of unsupervised and off-label use for cosmetic weight loss3. Although data on Tirzepatide’s efficacy and adverse effects are well published, evidence on duration of ongoing side effects of the drug, especially after discontinuation remains limited. This is a rare case presentation which illustrates persistent GI side effects and weight loss after discontinuation of Tirzepatide. Usually, the GI side effects reported in literature are dose-dependent and occur most commonly at higher doses and at initiation of therapy or up-titration of dose4.
This case also demonstrates how patients may seek weight-loss medications outside of formal healthcare settings with lack of awareness of their adverse effects and monitoring requirements. Initial review, regular monitoring of dosage and weight, and counselling patients of the adverse effects of Tirzepatide is essential to ensure safe use of the medication5. Without appropriate review and titration, users are at risk of undesired adverse effects such as excessive weight loss including loss of lean body mass (muscle) in addition to loss of adipose tissue, dehydration and severe electrolyte disturbance whilst taking the medication or even after discontinuation.
Appropriate follow-up with regular monitoring of weight, nutritional status, dosage, and early identification of adverse effects are crucial. Both health care providers and the public need to be better informed about the indication and the adverse effects of Tirzepatide as well as the importance of clinical supervision throughout treatment and discontinuation.
This case also serves as a reminder to clinicians that a thorough exploration of medical history including recently discontinued medications is critical to reach the diagnosis and understand a patient’s presenting symptoms. Some patients may omit the history inadvertently as they have stopped the medication 4 weeks ago. Without prompting for further medication history, Tirzepatide use may not have been discovered in this case, and the cause of the patient’s symptoms may not have been understood, leading to further unnecessary investigations for weight loss and diarrhoea.
Conclusion
In conclusion, while Tirzepatide (Mounjaro) is known to be an effective weight loss agent in appropriate patients as per local and national guidelines, its safe use requires regular follow-up and monitoring. Increased regulation is needed to prevent inappropriate access to the medication and patient education and further research on possibility of persistent side effects after discontinuation of the medication is warranted.
Key Learning Points
- Although adverse effects usually occur at initiation or dose up-titration of Tirzepatide, continued weight loss and GI side effects may occur after discontinuation. Limited evidence of such persistent side effects warrants further study.
- Given increasing commercial use, patients and healthcare providers should be well informed of the benefit, the risks, and the need for appropriate monitoring of Tirzepatide.
- Thorough exploration of medication history, including discontinued medications, over the counter, herbal, or privately sourced medications is crucial in reaching a diagnosis and identifying the cause of presenting symptoms.
References
- Cai W, Zhang R, Yao Y, Wu Q, Zhang J. Tirzepatide as a novel effective and safe strategy for treating obesity: a systematic review and meta-analysis of randomized controlled trials. Front Public Health. 2024 Jan 31;12:1277113. doi: 10.3389/fpubh.2024.1277113. PMID: 38356942; PMCID: PMC10864442.
- What are the general principles of managing a person who is living with overweight or obesity? (2025) NICE. Available at: https://cks.nice.org.uk/topics/obesity/management/management/ (Accessed: 17 November 2025).
- Almansour HA, Thaibah HA, Alfarhan M, Al-Qahtani SA, Khardali AA, Alshammari TM. Real-World Safety Concerns of Tirzepatide: A Retrospective Analysis of FAERS Data (2022-2025). Healthcare (Basel). 2025 Sep 9;13(18):2259. doi: 10.3390/healthcare13182259. PMID: 41008391; PMCID: PMC12469573.
- Wharton S, Davies M, Dicker D, Lingvay I, Mosenzon O, Rubino DM, Pedersen SD. Managing the gastrointestinal side effects of GLP-1 receptor agonists in obesity: recommendations for clinical practice. Postgrad Med. 2022 Jan;134(1):14-19. doi: 10.1080/00325481.2021.2002616. Epub 2021 Nov 29. PMID: 34775881.
- Tirzepatide for managing overweight and obesity (2025) NICE. Available at: https://www.nice.org.uk/guidance/ta1026/resources/a-practical-guide-to-using-medicines-to-manage-overweight-and-obesity-15299628589/chapter/Prescribing-reviewing-and-stopping-tirzepatide (Accessed: 17 November 2025).
Authors Information
Kyaw Thinzar Kyaw1, Kyi Lae Shune Kyaw2, Zin Zin Htike3
- MBChB, Foundation Year 2 Doctor, Barking, Havering and Redbridge University Hospitals NHS Trust, London, UK
- MBChB, Foundation Year 1 Doctor, NHS Lothian, Edinburgh, UK
- MBBS, FRCP, PhD, Consultant Physician (Diabetes and Endocrinology) & Training Program Director of East Midlands Deanery, Nottingham, UK
