Objectives: The aim is to determine the most common indications for biochemical testing by sex and age and the association between the concentrations of metanephrine and normetanephrine and indications, sex, and age. Study Design: Cross-sectional study with historical data. Participans and methods: The study was conducted on subjects in whom the concentration of metanephrine and normetanephrine in plasma was determined in 2019. A list of patients was collected from the Clinical Institute for Laboratory Diagnostics at the Osijek Clinical Hospital by accessing the laboratory information system. Data (indication for biochemical testing, sex, age) was collected from the Department of Nephrology for each patient by accessing the hospital information system. Results: The study was conducted on 224 respondents (42.9 % men and 57.1 % women). The most common indication for biochemical testing is adrenal incidentaloma (61.6 %) and symptoms of pheochromocytoma (18.3 %). There is no significant difference in the distribution of patients according to gender. The median age of participants with adrenal incidentaloma and participants with previously treated pheochromocytoma is higher compared to subjects with hereditary risk for pheochromocytoma and hypertension before they turned 20 years old. There is no significant association between the values of metanephrine and normetanephrine and the indication for biochemical testing. Metanephrine values are significantly lower in women. There is no significant association between age and metanephrine values, while the association between age and normetanephrine values is positive and significant, but very weak. Conclusion: Higher values of metanephrine are associated with males and higher values of normetanephrine are associated with older age. Adrenal incidentalomas and pheochromocytoma-indicating symptoms are very common in the general population, while the incidence of pheochromocytoma is extremely rare. Given the risk of missing a diagnosis, it is important to know the indications for biochemical testing to make a timely diagnosis and prevent complications.