Normal 24‑hour urinary sodium excretion ranges roughly from 40 to 220 mmol per day, which equals about 920 to 5,060 mg of sodium (approximately 2.3–13 g of salt). Urinary sodium largely reflects dietary intake and varies with diet, hydration, medications, and health conditions. Clinicians use 24‑hour collections to estimate sodium consumption.

Begin by discarding the first morning urine and note the time. Collect every urine in the provided container for the next 24 hours, including the first void the following morning at the same time. Keep the container refrigerated or on ice during collection. Record start/end times, avoid missed samples, note medications or dietary changes, and return the specimen promptly as instructed.

A 24-hour urine test measures total urine volume and daily excretion of substances—creatinine and creatinine clearance (kidney filtration), protein/albumin, electrolytes (sodium, potassium), calcium, oxalate, uric acid, hormones (cortisol, catecholamines) and metabolites. It helps evaluate kidney function, detect proteinuria, identify metabolic causes of kidney stones, screen for endocrine disorders and monitor medication effects to guide diagnosis and treatment.

Most sodium ingested is excreted in urine—about 90–95% in healthy adults. A 24‑hour urinary sodium varies with intake, commonly about 40–200 mmol/day (≈900–4,600 mg sodium). Many adults cluster around 100–150 mmol/day (≈2,300–3,450 mg). Urinary sodium is used to estimate dietary intake; values rise with higher salt intake and fall with restriction.

Serum sodium normally varies only a few mmol/L in 24 hours (typically 1–3 mmol/L). Illness, diuretics, fluid shifts or treatment can cause larger changes. To avoid osmotic brain injury, guidance is to limit correction to about 8–10 mmol/L (some acute protocols allow up to 10–12 mmol/L) in 24 hours; larger swings are possible but risky and need medical supervision.

To calculate 24‑hour urine levels, collect all urine for 24 hours (discard the first morning void, then collect every void until the same time next day; refrigerate). Measure total volume and obtain the analyte concentration. Multiply concentration (e.g., mg/L) by total volume in liters to get total mg per 24 hours. Report units and repeat if collection was incomplete.