Abstract
<jats:p>Carbimazole is a widely used medication to treat Graves disease. Acquired aplastic anemia is a rare complication that happens in less than 0.01% of people. We had a 36-year-old woman. Who is on high-dose Carbimazole . who got high-grade fever; severe menorrhagia ; spontaneous epistaxis; and pancytopenia . Her bone marrow biopsy showed severe bone marrow failure with only 5% cellularity and trilineage hypoplasia. Other potential causes were rolled out. Immediate discontinuation of Carbimazole was done; and supportive care; including blood transfusions; broad-spectrum antibiotics; G-CSF; and eltrombopag; was started. The patient deteriorated during her hospital stay; developed neutropenic sepsis and acute respiratory failure from diffuse alveolar hemorrhage; which required intubation and pulse steroid therapy. She was stabilized and discharged; with a referral to a tertiary medical center for starting antithymocyte globulin (ATG) immunosuppressive therapy. This case serves as a stark reminder of how lethal thionamide-induced bone marrow failure can be; highlighting the vital need for immediate drug cessation; swift intensive care; and thorough patient education on early warning signs.</jats:p>