Sodium: What It Is and What Your Results Mean
Bottom line: Sodium controls your body's water balance, blood pressure, and nerve function. Normal is 135-145 mEq/L. Abnormal levels usually reflect a water problem, not a salt problem.
What Is Sodium?
Sodium is the main electrolyte in your blood and the fluid surrounding your cells. It controls how water moves through your body, keeps your blood pressure stable, and allows nerves and muscles to fire properly. Your kidneys, working with hormones like ADH (antidiuretic hormone), keep blood sodium within a remarkably narrow window.
When sodium is low (hyponatremia), the problem is usually too much water diluting your blood rather than too little salt. Common triggers include certain medications, heart, liver, or kidney conditions, and hormone imbalances. When sodium is high (hypernatremia), the body has typically lost water faster than it could be replaced.
Because sodium directly affects the brain's water balance, significant abnormalities in either direction can cause confusion, headaches, and in severe cases seizures. Sodium disorders are among the most common electrolyte problems doctors see, especially in older adults and hospitalized patients.
Sodium Reference Ranges
| Classification | Range (mEq/L) |
|---|---|
| Severely Low (Severe Hyponatremia) | Below 120 |
| Low (Hyponatremia) | 120 - 134 |
| Normal | 135 - 145 |
| High (Hypernatremia) | 146 - 154 |
| Severely High | 155 - 180 |
What Affects Your Sodium Levels?
- Hydration status and how much water you drink
- Diuretics (water pills) and many blood pressure medications
- Antidepressants and seizure medications (can trigger low sodium)
- Kidney, heart, and liver function
- Hormone disorders affecting ADH, cortisol, or thyroid
- Vomiting, diarrhea, and heavy sweating
When to Get Tested
Sodium is included in every basic metabolic panel (BMP) and comprehensive metabolic panel (CMP), typically checked at annual physicals. More frequent testing is recommended if you take diuretics or antidepressants, have kidney, heart, or liver disease, or have had an abnormal result before.
Look Up Your Sodium Result
Select your value below to see a detailed breakdown of what it means:
Read the Full Blood Test Guide
Frequently Asked Questions
135 to 145 mEq/L is the standard normal range for blood sodium. Values below 135 indicate hyponatremia and values above 145 indicate hypernatremia. Levels below 125 or above 155 are treated as medical emergencies.
Usually not. Low blood sodium most often reflects excess water in the blood rather than a lack of salt, caused by medications, hormone imbalances, or organ conditions. The right treatment depends on the cause, which is why doctors investigate rather than simply prescribing salt.
Yes. Drinking large volumes of water faster than the kidneys can excrete it dilutes blood sodium. This is seen in endurance athletes who overhydrate and in people with conditions that impair water excretion.