To investigate the effects of glucose, parenteral amino acids, and intravenous insulin on albumin synthesis rates in critically ill children. Two studies were performed in 8 post-surgical infants (age 9.8±1.9 months; weight 9.5±1.1kg) and 9 septic adolescents (age 15±1yr; BMI 23±4kgm(-2)), respectively. All received a primed, constant, tracer infusion with [1-(13)C]Leucine. The infants in study 1 were randomized to receive low (2.5mgkg(-1)min(-1)) and standard (5.0mgkg(-1)min(-1)) glucose intake in a cross-over setting of two periods of 4h each. The adolescents in study 2 were randomized to receive total parenteral nutrition with standard (1.5gkg(-1)day(-1)) and high (3.0gkg(-1)day(-1)) amino acid intake in a two day cross-over setting. On both study days, during the last 3h of the tracer study, they received insulin infused at 80mUm(-2)min(-1). The post-surgical infants and the septic adolescents were mildly hypoalbuminemic (∼2.5gdL(-1)) with high synthesis rates, which were not affected by different intakes of glucose, amino acids, or insulin infusion. Albumin synthesis rates in hypoalbuminemic critically ill children are high but were not upregulated through nutrient supply, and in septic adolescents are unaffected by insulin.