A patient seated in the chair before a blood draw
In person

Sodium

Your main fluid-balance electrolyte, from one standard blood draw.

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  • 2,000+ lab locations. Find one near you
  • Nothing due at the lab. FSA / HSA accepted
  • Ordered by a licensed clinician

At a glance

Collection
Blood draw
A standard blood draw at the lab.
Preparation
None
Nothing to do ahead of time. Water is fine.
Results
1 to 2 days
Typical turnaround after your visit.
Where
2,000+ lab locations
Nationwide, with nothing due at the lab.

About this test

Sodium is the main electrolyte that controls how water is spread between your blood and tissues. The kidneys and several hormones keep it in a narrow range, so a change often reflects fluid balance, hormones, or medicines. It is usually read with other electrolytes rather than alone. No fasting is needed.

For adults 18 and older. Test availability varies by lab location.

Who should take this test?

This test is for adults whose healthcare provider wants to check sodium, often for hydration questions, medication check-ins, or to follow a past electrolyte result.

Ask about this test

Not sure this is the right test?

AI-generated. For information only, not medical advice. Call 911 for an emergency.

What does this test measure?

Your result shows how much sodium is in your blood, which can help a healthcare provider read your fluid balance alongside your other electrolytes and kidney markers.

Sodium
Sodium is an electrolyte that helps control the balance of water in and around your cells and supports nerve and muscle function. Blood sodium reflects your fluid balance as much as the salt you eat, and it can shift with hydration, some medicines, and conditions that affect the kidneys or hormones.
Why it’s measured: A core electrolyte for checking fluid and electrolyte balance.

How it works

  1. Step 1

    Order online

    Check out here. A licensed clinician in your state reviews your order and sends it to the lab.

  2. Step 2

    Visit a lab

    Bring a photo ID to any of 2,000+ lab locations. No fasting needed, and nothing is due at the lab.

  3. Step 3

    Get your results

    Results post to your account, usually in 1 to 2 days, each number next to the lab’s reference range.

Find a lab near you

Choose from 2,000+ lab locations nationwide. Your order works at any of them.

What your results tell you

Sodium is reported in millimoles per liter (mmol/L) and compared with the lab’s reference range, which is shown on your report.

  • Your number next to the lab’s reference range
  • Explained in plain language
  • A licensed clinician reviews your order and, if appropriate, orders the test.
  • A lab report you can download and share

An out-of-range sodium result can need prompt follow-up with a healthcare provider, who can explain what it means for you.

Clinical-grade testing, from the comfort of home.

From the lab to your report, every step of our process meets the gold standard in medical testing.

  • CLIA-certified labs

    Every lab we partner with is certified under the Clinical Laboratory Improvement Amendments, meeting both state and federal standards with regular independent inspections.

  • We protect your health data

    We protect your health data with encryption and do not sell it. Some results must be reported to public health authorities by law. See our Privacy Notice.

  • Rigorous quality assurance

    All partner labs run regular internal quality checks, participate in proficiency testing, and comply with federal and state lab regulations.

  • Clinician-reviewed reports

    Results are reviewed by an independent, licensed clinician.

Questions

Common questions.

Anything else, our care team answers by phone, text, or email.

Sodium helps control how much water stays in your blood vessels and how much moves into your cells and tissues. It also helps nerves and muscles send signals. The kidneys, along with hormones that act on them, adjust how much sodium and water your body keeps.

A sodium result reflects water balance as much as salt. Dehydration is one cause of a change, and holding on to extra water can lower sodium. Several hormone and kidney conditions can affect it too. A healthcare provider reads your result with your history and other results.

No. This test is not for emergencies. If you have chest pain, a racing or irregular heartbeat, fainting, severe weakness, or sudden confusion, get emergency care right away rather than waiting for a lab visit or a result.

No. Your kidneys adjust how much sodium they keep, so blood sodium usually stays in a narrow range across a wide range of diets. A blood sodium test does not measure salt intake or blood pressure. A healthcare provider reads it as a sign of fluid and hormone balance.

Lab tests are informational and don’t diagnose conditions on their own. Available to adults 18 and older; test availability varies by lab location. A licensed clinician reviews your order and, if appropriate, orders the test. All testing is performed at CLIA-certified laboratories. Not for emergencies: if you think you may be having a medical emergency, call 911.