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COMPREHENSIVE METABOLIC PANEL (CMP)
Also printed as: Na · Serum sodium
Educational only — not medical advice.
Sodium is the main electrolyte in the fluid outside your cells. Your body uses it to hold the right amount of water in the right places and to help nerves and muscles signal. The number reflects the balance between sodium and water more than how much salt you eat.
Sodium is tightly regulated, so even small shifts get attention — but small shifts also have very ordinary causes. It is best read together with potassium, chloride, and CO2, which together describe your fluid and acid-base balance.
TYPICAL ADULT RANGE
Many labs report roughly 135–145 mmol/L for adults. Ranges vary by lab, and the window is narrow by design. Reported in mmol/L.
Reference ranges vary by lab, by method, and by age and sex. Always read your own result against the range printed on your report.
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Slightly low sodium is common and often about water, not salt. Drinking a large volume of plain water before the draw, endurance exercise, hot weather, and several widely used medications (including some diuretics and antidepressants) can dilute it. Certain hormone patterns also play a role. Mildly low readings frequently normalize on a repeat draw; a value that stays low, or one paired with confusion, headache, or nausea, is worth raising with your doctor promptly.
Higher sodium usually points to less water rather than more salt — mild dehydration is the most common explanation, especially after a hot day, illness with fluid loss, or a long stretch without drinking. Some medications and a very high-salt intake with limited fluid can contribute. Your doctor will look at it next to your other electrolytes and your hydration on the day, and will often simply want a recheck.
Your doctor is the one who can read this number against your history, symptoms, and medications.
Educational only — not medical advice. Lab results only mean something alongside your history, symptoms, medications, and the rest of your panel. Bring questions to your doctor; they are the one who can interpret your results for you.
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