Sodium, Serum
Serum sodium measures the amount of the electrolyte sodium in your blood. Sodium helps control the balance of fluid in and around your cells and supports nerve and muscle function.
Sodium is tightly regulated by your kidneys, hormones, and thirst. Its level reflects the balance between sodium and water in your body more than how much salt you eat, so it's a key marker of fluid balance.
A higher sodium often reflects too little water relative to sodium, such as from dehydration or not drinking enough. It can also relate to certain hormonal or kidney conditions. Your clinician interprets it with your hydration and other electrolytes.
A lower sodium is common and can result from excess fluid, certain medications, or various medical conditions; it's interpreted in context and isn't always a concern when mild.
A typical range is roughly 135 to 145 mmol/L. Your clinician can tell you what your value means.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.