The global mortality of patients with cardiovascular diseases annually exceeds tens of millions. This study tested the hypothesis that fasting-induced down-regulation of pyruvate dehydrogenase (PDH) enzyme activity preconditions mice to improve survival during acute hypoxia. PDH is a major supplier of substrates to the TCA cycle but also generates toxic reactive oxygen species (ROS). PDH inhibition could inhibit ROS production, thereby contributing to fasting-induced protection against hypoxic death. FVB mice fasted for 48 hr displayed 100% survival during 1 hr 5% oxygen exposure compared to their fed counterparts that perished within 20 min, however, fasted C57BL/6J (B6) survival was minimal. Fasting induced an upregulation of PDH kinase 4 (PDK4) gene expression, increased PDH E1? site 3 phosphorylation, and decreased PDH activity in cardiac tissue of both mouse strains. Therefore, although PDH likely plays a role in hypoxia tolerance, it is not the primary mechanism of survival of the FVB mice.