Abstract Disclosure: F. farhat: None. P. Gonzalez: None. A.B. Ravin: None. F.F. Foo: None. S. Patel: None. J. Cheng: None. S.W. Holland: None. A. Chinnici: None. A. Abu Homoud: None. Introduction: Obesity and metabolic syndrome are serious conditions resulting in high morbidity and mortality. Approximately 70% of Americans suffer from obesity. In light of increasing obesity rates, many new medications, including GLP1 receptor agonists, have been approved by the FDA. Tirzepatide injection, known as Mounjaro, is a new medication for diabetes mellitus which offers additional benefits of weight loss. Mounjaro’s side effects can range from mild symptoms including nausea, vomiting, and diarrhea, to more severe symptoms like pancreatitis, and allergic reaction. In this report we present a rare case of renal failure after initiation of Mounjaro. Case presentation:This is a 59 year old male with past medical history significant for hypertension, dysglycemia who presented to the Emergency Department (ED) after two near syncopal events. He was started on Mounjaro a month ago. One week prior to presentation, the patient received his 6th dose of Mounjaro and shortly after he began experiencing generalized weakness associated with nausea, vomiting, diarrhea, and lower extremity cramps. His symptoms continued to worsen which prompted him to come to the hospital. Moreover, he had not voided in 4 days. In the ED, he was severely hyponatremic and AKI with a sodium of 115 and creatinine of 6.62.Patient was admitted to the ICU for further treatment and monitoring. He was evaluated by a nephrologist and determined that dialysis was not necessary as his AKI was resultant from volume depletion due to severe diarrhea as creatinine improved to 3.89 after resuscitation. He was discharged with no further complications.Discussion:This case report brings attention to a potential serious adverse effect from the use of a GLP1, Mounjaro, that has not been described before. Previous reports have described AKI caused by GLP1 treatment but none to our knowledge have discussed renal failure in patients without underlying renal disease. Patients with Chronic Kidney Disease and use of medications such as NSAIDs, diuretics, or angiotensin receptor blockers are more likely to develop renal complications.Mounjaro and other GLP1 medications have gained popularity among patients as they are effective in weight loss and simple to administer.. Additionally, more practitioners are now prescribing these medications for diabetics as they offer a more favorable safety profile compared to other available medications. Although GI side effects are well known, patients should be warned about the potential of severe dehydration leading to renal complications. Conclusion: Mounjaro has been associated with gastrointestinal adverse effects which include nausea, vomiting and diarrhea, and if severe, can lead to AKI and possible renal failure even without underlying renal disease. Monitoring renal functions after initiating or escalating the dose of Mounjaro should be a routine workup by all providers. Presentation: 6/2/2024