Validation of Capillary Serum Sodium Levels

Prospective interventional study to determine sodium levels in capillary blood via finger prick. The goal is to determine if this technique is suitable and equal to a standard venous blood collection for the analysis of blood sodium levels.The purpose is to compare both sodium levels to determine if they are equal so the technique can be used in a clinical setting for people who need regular blood collections for the determination of sodium, for example after the start of desmopressin use.