Sodium is the main positively charged ion outside the cells and the chief determinant of blood osmolality. Its concentration reflects the balance between body water and salt rather than total salt content, and is governed largely by thirst, antidiuretic hormone and the kidneys. It therefore speaks for water regulation and for the adrenal and renal systems that steer it.
No readings for this marker yet.
Raised sodium most often reflects a water deficit — insufficient drinking, fever, profuse sweating, vomiting or diarrhoea, or diabetes insipidus — rather than excess salt. Lowered sodium most often accompanies water retention: heart, liver or kidney failure, inappropriate antidiuretic hormone secretion, adrenal insufficiency, and treatment with diuretics. Marked shifts in either direction affect the brain and are followed closely. A single borderline result is a reason to re-test and talk to a doctor.
Very high blood fats, protein or glucose can lower the measured value artefactually, and drawing blood from an arm receiving an infusion distorts it badly. Diuretics, ACE inhibitors and desmopressin all shift the result, as do vomiting and diarrhoea on the day of the draw. Sodium is interpreted together with potassium and chloride, and alongside kidney markers and, where relevant, blood or urine osmolality.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.