McCoy's 5A (modified) Medium is a general purpose medium that supports the propagation of many types of primary cells, established cell lines, and explants from biopsy tissues. This medium will support the growth of primary mammalian cells derived from normal bone marrow, skin, spleen, kidney, lung, rat embryos, and other tissues.

The complete formulation is available.

Using McCoy's 5A (modified) Medium
Dr. Thomas McCoy originally formulated McCoy's 5A medium as a modification of Basal Medium 5A. Unlike other media, McCoy's 5A contains the reducing agent glutathione, bacto-peptone, and a high level of glucose. This product also includes Dr. Hsu's addition of Hanks' salts to enable use outside a CO₂ incubator. McCoy's 5A (modified) Medium requires serum supplementation, commonly with 10% Fetal Bovine Serum (FBS). McCoy's 5A (modified) Medium uses a sodium bicarbonate buffer system (2.2 g/L), and therefore requires a 5–10% CO₂ environment to maintain physiological pH.