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Electrolytes
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This test measures the amount of sodium in a whole blood sample analyzed on a blood gas instrument. Sodium is a major electrolyte that helps regulate fluid balance, nerve signaling, and muscle function.
Because it is run on whole blood, often from an arterial, venous, or capillary sample, results can be available quickly at the bedside. This method uses direct ion-selective electrodes, which can differ slightly from routine serum chemistry methods.
The test is commonly included with blood gas panels in emergency and critical care settings, but it can also be ordered to check electrolyte status when rapid decisions are needed.
Sodium levels help your care team assess hydration, kidney function, and certain hormone problems. Abnormal results can be linked to conditions such as dehydration or overhydration, heart or liver disease, adrenal or pituitary disorders, and effects of medicines.
Clinicians order this test when you have symptoms like confusion, headache, weakness, seizures, or when you are receiving treatments that can change sodium, such as intravenous fluids or diuretics. Rapid testing supports timely adjustments to fluids and medications, and helps prevent complications affecting the brain and other organs.
Your result is interpreted in the context of your symptoms, physical exam, and other labs such as potassium, chloride, glucose, and kidney markers. Whole blood results from a blood gas analyzer may not be identical to serum chemistry results because the sample type and measurement technique are different, so your team may compare both if needed.
If your level is outside the expected range, your clinician will consider possible causes like fluid shifts, medication effects, or underlying illnesses, then may repeat testing or order confirmatory tests. Newborns and certain clinical situations can have different expected values. Do not change fluids or medicines on your own; discuss next steps and monitoring with your care team.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Results can vary slightly between arterial, venous, and capillary samples. Delays to analysis can alter some blood gas parameters, so prompt testing is preferred even though sodium is relatively stable.
Drawing from a line recently flushed with saline or other sodium-containing solutions can falsely raise sodium. Using a peripheral stick or discarding an adequate waste volume reduces this risk.
Using syringes or tubes with inappropriate additives, or sodium heparin in excess, can affect results. Lithium heparin syringes designed for blood gas testing help maintain accuracy.
Dehydration, kidney disease, heart or liver failure, and disorders of hormones that control water balance can shift sodium levels. Recent fluid losses or gains are important context.
Diuretics, corticosteroids, desmopressin, lithium, laxatives, and hypertonic or hypotonic IV fluids can change sodium. Share all prescriptions and over-the-counter products you use.
Newborns and critically ill patients may have different expected ranges and faster shifts. High glucose or marked lipids and proteins can influence some serum methods; direct whole blood methods are less affected.
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