Cordycepic acid, also known as D-mannitol, is a bioactive compound found in Cordyceps species, especially Cordyceps sinensis. Its use to support the kidney system is primarily rooted in Traditional Chinese Medicine (TCM), where Cordyceps has long been valued as a kidney tonic. Historical TCM texts describe Cordyceps as beneficial for "nourishing the kidneys," improving vitality, and treating conditions associated with kidney deficiency such as fatigue and frequent urination. While some modern studies explore Cordyceps extracts for potential renoprotective effects—such as reducing markers of kidney damage or supporting renal function in animal models—few specifically isolate cordycepic acid as the active ingredient. The available scientific evidence is limited, often involving small sample sizes, animal studies, or non-standardized extracts. Thus, direct scientific validation for cordycepic acid's kidney-supporting effects is weak. The traditional rating reflects the long history of Cordyceps (and by extension, cordycepic acid) being used for kidney health in herbal medicine. However, the lack of robust clinical trials focused specifically on cordycepic acid means that scientific substantiation remains preliminary. More rigorous research is necessary to clarify its role and efficacy in supporting kidney function.