Analysis index

1 ml serum
1 ml plasma (Heparin or EDTA)

Copeptin, mornings, empty-stomached after 8 hours without liquids
< 2,6 pmol/l: Central diabetes insipidus totalis
> 20 pmol/l: Renal diabetes insipidus
2,6 pmol/l – 20 pmol/l: Evaluation of the copeptin index

Copeptin basal, without prior avoidance of liquids
< 21,4 pmol/l: Evaluation of the stimulated copeptin
≥ 21,4 pmol/l: Renaler diabetes insipidus

Hypernatremia, polyuria and polydipsia of unknown origin, suspicion of central or renal diabetes insipidus, suspicion of primary (habitual) polydipsia

Copeptin values should usually only be interpreted in the context of a thirst test, unless there is a preexisting hypernatremia (≥ 150 mmol/l) with clinical exsiccosis. Recently, however, copeptin stimulated by a 3% NaCl infusion has been recommended as an even more sensitive and specific diagnostic standard.