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Nutrients

Sodium

Also known as: Serum sodium test, Blood sodium test, Na⁺ test, Electrolyte panel (when part of a group of tests)

Almost always ordered as part of either a basic or comprehensive metabolic panel (BMP or CMP), sodium levels are measured via a blood test. Sodium, one of the body’s main electrolytes, helps regulate fluid balance, nerve signaling, and muscle contraction. Because sodium is so essential, even small shifts in its level can cause noticeable symptoms or indicate serious health problems.

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Key takeaways

  • Sample required: Blood (serum or plasma)

  • Tests for: Sodium levels in the blood, which reflect hydration, kidney function, adrenal health, and overall fluid balance

  • Healthy range: Generally, 135 to 145 milliequivalents per liter (mEq/L), though exact ranges vary by lab

What can a sodium test tell you?

Sodium levels don’t necessarily indicate a condition on their own, but they can help healthcare providers evaluate:

  • Fluid status. Sodium reflects the balance between water and sodium in the body, so changes often indicate fluid shifts rather than changes in total body sodium alone. 

  • Kidney and hormone regulation. Sodium is tightly controlled by the kidneys, working in response to aldosterone, antidiuretic hormone (ADH), and the renin-angiotensin system. 

  • Heart and liver health. Low sodium is common in heart failure and cirrhosis due to altered fluid balance. 

  • Medication monitoring. Certain medications, including diuretics, antidepressants, and seizure medications, can all shift sodium levels.

  • Endocrine and metabolic disorders. Conditions like SIADH (syndrome of inappropriate antidiuretic hormone secretion) or diabetes insipidus can lead to dangerously abnormal sodium levels.

What is being tested?

When sodium levels are tested as part of a BMP or CMP, a provider is looking at the concentration of sodium in the blood. Sodium is an electrolyte — a charged mineral — that helps regulate water movement inside and outside of cells. Too much or too little sodium can disrupt the body’s balance.

Key functions of sodium include:

  • Maintaining proper fluid balance 

  • Supporting nerve impulses that allow your brain and body to communicate 

  • Helping muscles, including the heart, contract and relax

Where is the sodium test typically included?

Most sodium measurements come from standard lab panels:

  • Basic metabolic panel (BMP). Includes sodium, potassium, chloride, bicarbonate, blood glucose, calcium, and kidney markers.

  • Comprehensive metabolic panel (CMP). Includes all BMP tests plus liver function markers.

  • Electrolyte panel. Specifically measures sodium, potassium, chloride, and bicarbonate.

Who should get their sodium tested?

Sodium levels are most commonly tested as part of a basic metabolic panel or comprehensive metabolic panel. However, your provider may want to evaluate your sodium levels if you:

  • Show symptoms such as confusion, nausea, headache, muscle weakness, or seizures 

  • Have risk factors such as kidney disease, heart failure, liver disease, or adrenal disorders 

  • Are taking medications known to affect sodium (e.g., diuretics, certain antidepressants, anti-seizure drugs) 

  • Experience unexplained swelling, dehydration, or changes in urination, which may indicate an electrolyte imbalance

Routine sodium testing isn’t recommended for healthy people without risk factors. However, many people have sodium measured incidentally during annual physicals, hospital admissions, or monitoring of chronic conditions.

Guidelines emphasize that interpretation depends on the individual. For example, the U.S. Preventive Services Task Force (USPSTF) doesn’t recommend routine sodium blood testing for the general population. 

However, they recommend in-office blood pressure testing using a sphygmomanometer for people 18 and over, with follow-up testing for those with abnormal results.

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Not available in all 50 states. Eligibility and provider order required. Lab results alone are not intended to diagnose, treat, or cure any condition. A provider will reach out about critical results and plans include access to 24/7 provider messaging.

Images for illustrative purposes only.

Frequently asked questions

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What Causes Changes in Sodium Levels?

Causes of increased sodium levels (hypernatremia) often stem from dehydration, whether due to inadequate water intake or excessive fluid loss from vomiting, diarrhea, or sweating. Kidney disease can also play a role by impairing the body’s ability to conserve water. Hormonal imbalances, such as diabetes insipidus or hyperaldosteronism, may contribute to elevated sodium levels as well. In some cases, consuming too much salt without sufficient fluid replacement can further drive sodium concentrations upward.

Conversely, decreased sodium levels (hyponatremia) can occur in conditions like heart failure, liver cirrhosis, or kidney disease, all of which can disrupt fluid balance. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is another common cause, leading to water retention and diluted sodium levels. Certain medications, including thiazide diuretics, SSRIs, and some seizure drugs, can also lower sodium. Additionally, excessive water intake — though rare — may result in dilutional hyponatremia, particularly among endurance athletes or individuals with psychiatric conditions. Prolonged vomiting, diarrhea, or sweating can also lead to sodium loss over time.

What is the reference range for sodium levels?

The normal reference range for sodium levels in adults is 135 to 145 mEq/L, though exact ranges vary by lab. 

Can a sodium test be done at home?

Some telehealth companies offer at-home sodium collection kits as part of an electrolyte panel. However, the most accurate testing is performed in clinical labs.

Do I need to fast before a sodium test?

No fasting is required.

How long does it take to get results?

Lab results are often available within a few hours to one day 

How often should I get tested?

It depends on your health. People with chronic conditions or on medications that affect sodium may need regular monitoring, but healthy adults without risk factors usually don’t need routine sodium checks.

Does insurance cover a sodium test?

Yes, when medically necessary (e.g., symptoms, chronic illness, or part of a standard metabolic panel). Insurance is not required with lab testing through Hims. 

What’s the difference between sodium intake and sodium blood levels?

Dietary sodium (from food and salt) influences blood pressure but doesn’t always directly match blood sodium levels. Blood sodium reflects overall fluid and electrolyte balance, not just diet.

What symptoms might prompt a sodium test?

Confusion, fatigue, headache, nausea, seizures, muscle cramps, or swelling may all lead a provider to order a sodium test.

What tests are related to this biomarker?

• Potassium

• Chloride

• Carbon dioxide (bicarbonate)

• Glucose

• Calcium

• Creatinine

• Blood urea nitrogen (BUN)

• Serum osmolality 

• Urine sodium

• Aldosterone and renin

• Antidiuretic hormone (ADH) / vasopressin

The information provided here is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always talk to a qualified healthcare provider about your specific health concerns.

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Reviewed by Darragh O'Carroll, MD

Published 11/19/2025