Sodium normal range
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Serum Sodium Normal Range: Clinical Chemistry and Diagnostic Reference
The normal range for serum sodium in healthy adults is generally considered to be 137–147 mEq/L, based on laboratory studies of healthy individuals. However, for practical diagnostic purposes, especially in clinical settings where mild illness may be present, a slightly narrower range of 135–144 mEq/L is often used to account for non-specific effects of illness without including values that are pathologically low 12. This range is widely accepted and used in most clinical laboratories.
Sodium Reference Range in Hospitalized and Older Populations
Studies show that serum sodium levels in hospital inpatients are often lower than those in healthy outpatients, largely due to underlying illnesses that can lower sodium concentrations. Inpatients with normal serum urea still have mean sodium levels about 8.5 mEq/L lower than healthy controls, and the 95% reference range for inpatients is typically 127–143 mEq/L, while for outpatients it is 129–145 mEq/L 12. Among older adults, the lower end of the normal range (135–140 mEq/L) is associated with higher prevalence of geriatric syndromes such as dependency and malnutrition, while the upper normal range (141–145 mEq/L) is linked to lower risks of these conditions . In hospital settings, the risk of mortality begins to rise at sodium concentrations above 139 mmol/L, even within the normal reference range, suggesting that the optimal range for older or hospitalized patients may be narrower or shifted compared to healthy populations .
Sodium Intake: Dietary Reference and Population Ranges
Dietary sodium intake, as measured by 24-hour urinary sodium excretion, is remarkably consistent worldwide, with most populations consuming between 114–210 mmol/day (2,622–4,830 mg/day) . Health organizations often recommend a sodium intake below 2.0–2.3 g/day (about 5–5.8 g/day of salt) to reduce cardiovascular risk, but evidence suggests that the lowest risk of cardiovascular disease is seen with moderate sodium intake in the range of 3–5 g/day 67910. Intakes above 5 g/day or below 3 g/day are associated with increased health risks 79. The European Food Safety Authority considers 2.0 g/day a safe and adequate intake for adults, with lower values extrapolated for children .
Serum Sodium and Health Outcomes
Serum sodium is tightly regulated by the body, typically maintained within 135–145 mmol/L through osmoregulation . Even within this normal range, higher sodium levels are associated with increased cardiovascular risk factors such as higher cholesterol and blood pressure . In older adults, higher-normal sodium levels are linked to better functional outcomes, while both low and high extremes are associated with increased health risks 48.
Conclusion
The normal serum sodium range for healthy adults is 137–147 mEq/L, but for clinical and diagnostic purposes, a range of 135–144 mEq/L is often more practical. Hospitalized and older populations may have slightly different optimal ranges due to illness and age-related changes. Dietary sodium intake recommendations generally aim for less than 5 g/day, with the lowest health risks observed in the moderate intake range of 3–5 g/day. Maintaining serum sodium within the normal range is important for overall health, as both low and high values are associated with increased risks of adverse outcomes.
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