ColistinDose is a clinician-friendly, easy-to-use iPhone app with the up-to-date dosing recommendations of intravenous colistimethate in critically-ill patients. It is intended for use by healthcare professionals only. Determination of the dosage regimens of intravenous colistimethate in critically-ill patients is complicated, and requires thorough understanding of the pharmacokinetics of colistimethate and formed colistin and the confusing dose unit definitions in different parts of the world (Lancet Infect Dis. 2006; 6:589-601). Integrating the state-of-the-art clinical pharmacokinetic/pharmacodynamic information (Clin. Infect. Dis., 2017; 64:565-571), ColistinDose provides an accurate and easy tool to clinicians on calculating the dosage regimens of intravenous colistimethate in critically-ill patients with different renal function and those on renal replacement therapy. ColistinDose features the following three major functionalities. For the convenience of clinicians in different regions of the world, all doses are provided with two commonly used conventions, i.e. colistin base activity (CBA) and international million unit (MU), to avoid the conversion. (1) Calculation of the loading dose based upon the targeted colistin steady-state concentration; (2) Calculation of the daily dose based upon the targeted colistin steady-state concentration and renal function, including those on different types of renal replacement therapy, such as IHD (intermittent hemodialysis), SLED (sustained low-efficiency dialysis) and CRRT (continuous renal replacement therapy); (3) Retrieval of historical calculation results, which allows clinicians to easily revisit previously calculated colistimethate doses and make appropriate dose adjustments.