A higher than normal percentual contribution of isoform A to the lactate dehydrogenase enzymatic cluster reveals a pathological shift towards fermentative metabolism somewhere within the organism of the host. The hypermetabolic phenotype expressed by tumour cells, a well-documented hallmark of cancer, is rooted on the catalytic action of several enzymes, amongst which hexokinase 2 and LDH-A are key players, supporting cell survival and neoangiogenesis as well as driving tumour growth. The physiological, intrinsic secretion of lactic dehydrogenase A in healthy humans has not been described formally and can be used as a functional frame of reference in the ultra-early detection of neoplastic transformation. In healthy subjects, even with total plasma LDH within the normal range, increases in the isoform A surpassing three or more standard deviations above its mean percentual contribution to the enzymatic cluster suggest a pathological reprogramming of energy metabolism. Herein, preliminary evidence is presented, supporting the notion of LDH-A as a screening tool for ultra-early, actionable detection of microtumours, during the initial or avascular phase of neoplastic progression.