Table 1

 Overview of the causes of hypernatraemia in primary care and guide to suggested action levels*

Hypernatraemia: causes
*Thresholds for action and referral should, however, be based principally on clinical state and rate of change.
Hypernatraemia with a high/rising urea and only mild increase in creatinine is a useful adjunct to making a diagnosis of dehydration.
Net water lossDiuretics
Vomiting and diarrhoea
Prolonged fever or sweating
Failure to drink/poor access to fluids
Diabetes mellitus
Nephrogenic diabetes insipidus
Cranial diabetes insipidus
Salt excessSalt intoxication