Sodium
Sodium is the body's main extracellular electrolyte. Abnormal levels reflect water imbalance more than salt intake.
What it measures
Sodium is the dominant positively-charged ion outside your cells; its concentration drives most of your blood's osmotic pressure. Because the body tightly regulates sodium through thirst, kidney handling and antidiuretic hormone, the blood sodium level usually reflects water balance, not salt intake — hyponatraemia means too much water relative to sodium, not too little salt. Sodium is one of the few markers where small deviations matter: anything below 130 or above 150 mmol/L is clinically significant.
What a high value can mean
- Dehydration — the most common cause; insufficient water intake or excessive loss (vomiting, diarrhoea, fever).
- Diabetes insipidus — failure to concentrate urine.
- Excess sodium intake (rare in normal kidneys) — e.g. salt-water ingestion.
- Some medications — corticosteroids, hypertonic saline.
What a low value can mean
- SIADH (Syndrome of Inappropriate Antidiuretic Hormone) — most common in hospitalised patients.
- Heart failure, cirrhosis, nephrotic syndrome — fluid overload dilutes sodium.
- Excessive water intake (psychogenic polydipsia, marathon over-hydration).
- Adrenal insufficiency, hypothyroidism.
- Diuretics, particularly thiazides.
When to discuss with a doctor
Sodium outside 130–150 mmol/L warrants a primary-care or urgent visit — correction must be gradual because rapid changes (especially raising sodium too fast in chronic hyponatraemia) can cause irreversible neurological injury. Acute severe hyponatraemia (<120) with confusion is an emergency. Mediora.AI flags critical values directly in the report.