Abstract Disclosure: T. Chaudhary: None. O. Syed: None. M. Nawaz: None. R. Kaur: None. Introduction: Immunosuppressant use comes at a cost of challenging side effects, which are being discovered more as its use increases. One such example is our case of new-onset diabetes after transplant (NODAT).Patient presentation: A 36-year-old male with a past medical history of end-stage renal disease status post renal transplant (6/2023), hypertension, and hyperlipidemia who presented to the hospital in 10/2023 with fever, chills, and diarrhea. His vitals at that time were as follows: temperature 36.1C, blood pressure 148/84 mmHg, pulse 87 bpm, and a respiratory rate of 22. Lab work was significant for blood glucose 1144, anion gap 22, bicarbonate 13, potassium 7.3, Sodium 135, lipase 427, pH 7.3, urine ketones 80, HbA1C 11.5 %. CT scan of the abdomen revealed loss of peripancreatic fat and inflammatory changes surrounding the pancreas. His medication review included Tacrolimus 12 mg daily, Mycophenolate 500 mg BID, Valtrex 500mg daily, and fluconazole 200mg every other day. He was treated with 2 liters of normal saline bolus and started on maintenance fluid, and insulin drip as per DKA protocol. Calcium gluconate and an albuterol nebulizer were given for hyperkalemia. Tacrolimus and prednisone were held. Endocrinology and Nephrology were consulted. The patient was thought to have diabetes due to steroid use which were discontinued and the patient was discharged on subcutaneous insulin regimen and lower dose of tacrolimus. Despite discontinuation of steroids, patients continued to have raised glucose readings confirming the causative agent as tacrolimus. Conclusion: The current guidelines for post-kidney transplant patients recommend checking fasting blood glucose weekly for the first four weeks, then biweekly for two months, and then monthly thereafter. HbA1C should be checked every 3 months and if it is >6% then home glucose monitoring should be done as well. Although the frequency of these check-ups decreases, it is imperative for physicians to remember that patients can still develop NODAT months post-transplant. It is also essential to reinforce the importance of these glucose checks for the patient as missed diagnosis can lead to dangerous complications such as DKA. Presentation: 6/2/2024