Day care is a potential alternative to inpatient care of cancer patients. Using day care reduces medical costs substantially compared to inpatient care, which is driving the transfer of many inpatient chemotherapy protocols to day care hospitals (DCHs). However, in contrast to inpatient management, day care provides limited observation time, which could increase the risk of renal toxicity when using these protocols. We present a case report of acute kidney injury following high-dose methotrexate administration in a DCH. Based on a review of the current literature on acid-base balance, we also discuss appropriate patient selection and judicious hydration and urine alkalinization so as to prevent toxicity in the day care setting.