PURPOSE: Folinic acid (FA) rescue protocols to counter the adverse effects of high-dose methotrexate (HDMTX) vary widely, and the risk of over-rescue and potential adverse effects of excessive FA (e.g., hypercalcemia) are under-recognized issues when providing augmented rescue in cases of delayed methotrexate elimination (DME). This opinion summary defines over-rescue, describes its potential adverse impacts, highlights the risk of hypercalcemia associated with excessive FA dosing in patients with acute kidney injury (AKI) from HDMTX, and provides recommendations to improve safety and efficacy of FA rescue in patients receiving HDMTX. METHODS: A multidisciplinary panel of experts with clinical experience in HDMTX treatment convened in three roundtable meetings to coalesce expert opinion and best published evidence on the pharmacology and clinical effects and interactions of FA and HDMTX. RESULTS: The type of FA (calcium folinate, calcium levofolinate, sodium levofolinate), dose, and frequency of FA administration may be factors for over-rescue and the development of hypercalcemia due to their respective pharmacokinetic characteristics, especially in cases of DME requiring augmented FA rescue. CONCLUSION: Clinicians are reminded of the possibility of over-rescue with FA and its impact on subsequent HDMTX courses, types of FA available and their durations of action, and avoid providing too frequent doses. In the setting of AKI and DME requiring high doses of FA, use of sodium levofolinate or calcium levofolinate may be considered to reduce the risk of hypercalcemia associated with calcium folinate.