Whole body nitrogen has been measured absolutely in male volunteers and patients by in-vivo neutron activation analysis using
whole body hydrogen as an internal standard. The 10.8 MeV and 2.2 MeV prompt gamma rays from nitrogen and hydrogen respectively
give a result reproducible to 4% for a dose of 100 mRem. Whole body potassium measured by whole body counting natural40K and whole body nitrogen have been correlated in normal adult males and patients. In the normals the correlation coefficient
was 0.96 with coefficient of variation 4%. In the patients these parameters were 0.92 and 8% in 140 measurements. The ratio
of N/K increased significantly as the degree of clinical wasting progressed.