This is a case of 26-year-old unmarried, self-employed Asian (Bhutanese) woman, weighing 44 kg and 163 cm tall admitted to the medicine ward for nausea, vomiting, abdominal pain, chronic gastritis, anemia, hypertension, loss of appetite, and elevated serum blood urea and creatinine. The case was reported to the Pharmacovigilance Centre on 16 November 2020 as an adverse drug reaction. The patient underwent renal allograft replacement in 2013, and a second transplant was performed in 2015. Since then, she has been on regular oral antirejection and antihypertensive medication comprising tacrolimus (Tacrograf) 2 mg twice daily, prednisolone 5 mg once daily, leflunomide 20 mg once daily, nifedipine 40 mg twice daily, and hydralazine 50 mg three times daily. On the evening of 6 November 2020, she experienced nausea, vomiting, and severe abdominal pain and was brought to the emergency department, where physical examination was unremarkable, with no fever but a tender abdomen. Vital signs were as follows: blood pressure (BP) 152/94 mm/Hg, visual pain score 3/10, respiratory rate 18 breaths per minute; pulse rate 86 beats per minute; saturated partial oxygen (SpO2) 96%; and body temperature 96 °F. Laboratory findings were as follows: hemoglobin (Hb) 7.7 g/dl (11.3-14.9 g/dl); red blood cell (RBC) count 3.3 × 106/μl (3.76–4.84 × 106/μl); hematocrit (Hct) 24.7% (33–45%), white blood cell (WBC) count 21.4 × 103/μl (4–10 × 103/μl); serum creatinine (Cr) 8.6 mg/dl (0.6–1.2 mg/dl), and urea (Ur) 200 mg/dl (15–45 mg/dl). She received ceftriaxone 1 g intravenously once daily as an empirical antimicrobial therapy, paracetamol (acetaminophen) 300 mg intravenously three times daily, ranitidine 50 mg intravenously three times daily, thiamine 100 mg intravenously once daily, and intravenous infusion of lactate ringer with 5% dextrose in the emergency room along with antirejection medication. On 7 November 2020, she was transferred to the medicine ward. Her tacrolimus trough level was 3.07 ng/dl (4–8 ng/dl), Gravindex for urine sample was negative, 24-hour urine protein was 391 mg/dl (< 150 mg/dl), urine volume was 300 ml in 24 hours, and 24-hour protein was 1.7 g/24 hours (< 0.15 g/24 hours). The medication administered and laboratory reports in the medical ward are presented in Tables and. After 3 days, on 10 November, the patient complained of milk production from a single breast. When interviewing the patient on her past medication use and the drug reaction, she revealed that she experienced a similar reaction to omeprazole in 2013 after kidney transplant. Oral omeprazole was immediately discontinued. The amount of milk production started to decrease, and on 18 November 2020, production stopped completely. Adverse drug reactions were entered into the Vigiflow system and reported to the National Pharmacovigilance Centre. The causality assessment score on Naranjo’s algorithm was 10 (> 9 Definite). On 20 November 2020, the tacrolimus trough level was 5.9 ng/dl (4–8 ng/dl) at a 2.5 mg twice daily dose. She was discharged from the hospital on 26 November 2020 and continued to receive treatment and dialysis as an outpatient.