Vascular endothelial growth factor (VEGF) is known to be upregulated by hypoxia in vitro. However, in vivo data about VEGF regulation in chronic hypoxic diseases are conflicting. We investigated the effects of hypoxia on plasma VEGF concentration in healthy subjects. To control known confounders such as insulin, glucose concentrations or exercise, hypoxic effects on VEGF were studied during experimentally clamping glucose concentrations at rest. In a double-blind cross-over study design, we induced hypoxia for 30 minutes by decreasing oxygen saturation to 75% (versus normoxic control) in 14 healthy men. Plasma VEGF concentration was determined at baseline, immediately after hypoxia had ended and after further 150 minutes. Levels of its soluble Flt-1 receptor were assessed at baseline and at the end of the clamp. In parallel, catecholamine and cortisol levels were monitored. To investigate potential effects of glucose administration on the release of VEGF, we performed a third session reducing glucose infusion for 30 minutes while serum insulin was held stable thereby inducing hypoglycemia. Hypoxia decreased VEGF levels, as compared to the normoxic control (P<0.05). VEGF concentrations increased during hypoglycemia (P<0.02) but were comparable to the normoglycemic control at the end of the clamp (P>0.80). Soluble Flt-1 receptor concentration remained unchanged during hypoxia and hypoglycemia as compared to control (both P>0.4). Epinephrine concentration (P<0.01) increased upon hypoxia, whereas norepinephrine and cortisol did not change. Contrary to in vitro studies, in healthy humans, hypoxia decreases plasma VEGF concentration suggesting that systemic VEGF concentration may be differently regulated than the expression on cellular basis.