Blood or urine specimens are generally used for aldosterone determination in conjunction with their respective reference ranges. Plasma and urine aldosterone concentrations are influenced by body position and sodium intake, with aldosterone elevated when the body is in the upright position and low in sodium. The reference range for plasma aldosterone is 50 to 250 pmol/L in the prone position and 80 to 970 pmol/L in the upright position; the normal reference values for urinary aldosterone are 6.4 to 86 nmol/24h when sodium intake is normal, 47 to 122 nmol/24h when sodium intake is low, and 0 to 13.9 nmol/24h when sodium intake is high. When aldosterone is measured, it is necessary to combine the type of specimen and the normal reference range to determine whether it is normal.