📅 Last Updated: April 2026 | 🩺 Medically Reviewed by: Edward Salko, D.O., Medical Director | 🧪 Lab Partner: Labcorp
Sodium is the primary electrolyte controlling fluid balance, blood pressure, and nerve function. Even small deviations from the normal range cause significant symptoms — confusion, muscle cramps, weakness, and in severe cases seizures. The sodium
blood test measures serum sodium to identify hyponatremia (low) or hypernatremia (high) and monitor conditions or medications that affect electrolyte balance.
Available through Personalabs at any Labcorp location nationwide. No doctor visit required. Results in 24–48 hours.
The Purpose of a Sodium Test
Sodium in your food adds flavor, but sodium in your body adds balance — it’s an electrolyte that controls fluid and pH levels for optimal health. Sodium (aka the chemical symbol Na) can be tested as part of your annual blood work, or it may need to be checked if you have symptoms caused by high sodium levels (hypernatremia) or low (hyponatremia). For instance, low sodium can cause leg cramps and disrupt normal muscle and nerve function, while high sodium can elevate your blood pressure.
What Does the Blood Test for Na Measure?
The sodium test will tell you how much sodium is in your body.
Who Should Take a Sodium Level Test?
Confusion, muscle twitches, and seizures are signs that your sodium is either too high or too low, and can signal the need for a Na lab test. You may also monitor your levels if you have high blood pressure or a kidney disorder, which can be affected by the amount of sodium in your body. And you can preventively measure your levels during your annual checkup; sodium can be tested on its own or included in an electrolyte panel, basic metabolic panel, or comprehensive metabolic panel.
Sodium Lab Test Preparation
You don’t need to take any special steps before your blood test for Na.
Sodium Normal Range — What Your Results Mean
| Level | Classification | Clinical Meaning |
|—|—|—|
| Below 125 mEq/L | Critically Low | Severe hyponatremia — seizure and coma risk |
| 125–134 mEq/L | Low (Hyponatremia) | Confusion, headache, nausea, muscle cramps |
| 135–145 mEq/L | Normal | Healthy electrolyte balance |
| 146–149 mEq/L | Mildly High | Mild dehydration or excess sodium intake |
| Above 150 mEq/L | High (Hypernatremia) | Severe dehydration, diabetes insipidus |
| Above 160 mEq/L | Critically High | Medical emergency |
Who Needs Sodium Monitoring and Why
Sodium is one of the 14 markers included in the Comprehensive Metabolic Panel (CMP) — the standard annual blood test. A standalone sodium test is most useful when you need to monitor sodium specifically between full CMP draws or in response to a medication or condition affecting electrolytes.
People who need regular sodium monitoring:
Anyone on diuretics — loop diuretics (furosemide) and thiazide diuretics both affect sodium excretion. Hyponatremia is a common and sometimes dangerous side effect of thiazide diuretics especially in older adults.
People on SSRI antidepressants — SSRIs are a significant cause of hyponatremia through a mechanism called SIADH (Syndrome of Inappropriate Antidiuretic Hormone). Low sodium on SSRIs can mimic depression symptoms and worsens cognitive function.
Anyone with kidney disease — the kidneys regulate sodium excretion. Declining kidney function disrupts sodium balance in both directions.
Endurance athletes — prolonged exercise with excessive plain water intake without electrolyte replacement causes exercise-associated hyponatremia. A serious and occasionally fatal condition in marathon and ultramarathon runners.
People with heart failure — heart failure causes fluid retention and dilutional hyponatremia. Sodium monitoring is routine in heart failure management.
If you need a complete metabolic picture — kidney, liver, glucose, and all electrolytes — the CMP provides better value than standalone sodium.
Reviewed by Edward Salko, D.O., Medical Director, Personalabs
Where Can I Get a Sodium Blood Test Near Me?
We have a wide array of vitamin and nutrition tests among the 400-plus tests in our online store. Get the data you need to make informed choices about medications, lifestyle changes, and more from Personalabs. We deliver the power of healthcare and put it in your hands.
The process is simple:
Step 1: Choose the sodium level test and download the lab order that comes with it. (You may not even need a doctor’s approval before purchasing the test, depending on the state where you live.)
Step 2: Pinpoint the closest testing facility with our lab locator tool. (It shouldn’t be hard to find; our partnerships with Quest Diagnostics and Labcorp give you more than 4,000 locations to choose from.)
Step 3: Bring the test order to the lab and get your blood drawn.
Step 4: See your results report within 2 to 10 business days in your private Personalabs portal. (Need the results by a specific date? Just contact us, and we can work the lab on the turnaround time.)
Take a more proactive approach to healthcare. Browse the Personalabs website to see which health tests can help you feel your best, or ask our knowledgeable customer service team for assistance at any step of the process. Shop our full range of tests today.
Frequently Asked Questions: Sodium Blood Test
What is a normal sodium level in blood?
Normal serum sodium is 135 to 145 mEq/L. Below 135 mEq/L is hyponatremia — low sodium causing symptoms including confusion, headache, nausea, and muscle cramps. Above 145 mEq/L is hypernatremia — typically from dehydration. Below 125 and above 160 are critical values requiring immediate medical evaluation.
What causes low sodium levels?
The most common causes of low sodium (hyponatremia) are diuretic medications (especially thiazides), SSRI antidepressants (through SIADH), kidney disease, heart failure, liver cirrhosis, excessive water intake without electrolyte replacement, and adrenal insufficiency. Older adults are at highest risk because multiple contributing factors often coincide.
Is sodium included in the CMP?
Yes. Sodium is one of the 14 markers in the Comprehensive Metabolic Panel (CMP). If you need a complete metabolic evaluation including kidney function, liver function, glucose, and all electrolytes — the CMP provides better value. The standalone sodium test is useful when monitoring sodium specifically between CMP draws or tracking a medication effect.
Do I need to fast for a sodium blood test?
No fasting required. Available through Personalabs without a doctor’s visit — order online, visit any Labcorp location, results in 24 to 48 hours. HSA and FSA eligible.
