Lab marker · Low

Low Sodium: what it means

A Sodium result below the normal range is considered low. Here is what a reduced Sodium can point to, and when it is worth discussing with a doctor.

Reference range: 135–145 mmol/L; critically low <125 or high >155

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What a low Sodium 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.

Conditions this can relate to

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Mediora.AI is informational - interpretation, not a diagnosis. A single out-of-range value is common and often benign; always discuss decisions with your doctor.