Lactate in Context: Physiology and Clinical Judgment

Lactate is among the most frequently measured biomarkers in clinical care, yet its pathophysiologic interpretation remains frequently misunderstood. Historically regarded as a byproduct of anaerobic metabolism and a direct cause of acidosis, lactate is now recognized as a central intermediary in numerous physiologic processes. This review emphasizes a physiologic framework of lactate kinetics, highlighting the dynamic balance between production and clearance in the interpretation of hyperlactatemia. Clinically, lactate is best understood as a contextual biomarker reflecting both hypoxic and nonhypoxic processes, including catecholamine or malignancy-driven glycolysis, mitochondrial dysfunction, and impaired clearance. At the bedside, an elevated lactate should prompt a structured assessment of hemodynamic phenotype, incorporating both macrocirculatory and microcirculatory considerations. Interventions aimed solely at reducing lactate or its associated acidosis have not consistently demonstrated improved outcomes, whereas therapies directed at the underlying disease process are of critical importance. Ultimately, lactate should not be viewed as a therapeutic target in isolation but as a signal to guide physiology-driven clinical judgment.