Serum Sodium 

Updated: Dec 05, 2013
  • Author: Fazia Mir, MD; Chief Editor: Eric B Staros, MD  more...
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Reference Range

Measurement of serum sodium is routine in assessing electrolyte, acid-base, and water balance, and renal function. Sodium accounts for approximately 95% of the osmotically active substances in the extracellular compartment, provided the patient is not in renal failure or has severe hyperglycemia.

The reference range for serum sodium is 135-145 mmol/L.

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Interpretation

Conditions associated with increased serum sodium (hypernatremia) include the following:

Conditions associated with decreased serum sodium (hyponatremia) include the following:

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Collection and Panels

Specifics for collection and panels are as follows:

  • Specimen type: Blood serum
  • Container: Vacutainer, red/black top or red top
  • Collection method: Venipuncture
  • Specimen volume: 0.5 mL
  • Panels: Serum electrolytes, basic metabolic panel, complete metabolic panel
  • Other instructions:

Related tests are as follows:

  • Serum chloride
  • Serum potassium
  • Serum bicarbonate
  • Serum osmolality
  • Blood urea nitrogen (BUN)
  • Plasma glucose
  • Urine electrolytes
  • Urine osmolality
  • Aldosterone
  • Antidiuretic hormone (ADH)
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Background

Description

Measurement of serum sodium is routine in assessing electrolyte, acid-base, and water balance, and renal function. Sodium accounts for approximately 95% of the osmotically active substances in the extracellular compartment, provided the patient is not in renal failure or has severe hyperglycemia.

Regulation of sodium occurs by balancing water in the body with use of antidiuretic hormone and increasing or decreasing the renal excretion of sodium. Other factors involved in regulation are aldosterone, atrial natriuretic peptide, and renal hemodynamic factors. Measurement of serum sodium is done by ion-specific electrodes now; therefore, it is less influenced by high concentrations of lipids or proteins compared with flame photometry, which was used earlier to determine serum sodium. [1]

Indications/Applications

Indications for testing of serum sodium/serum electrolytes are as follows:

  • Routine evaluation
  • Assessing water balance
  • Assessing acid-base balance
  • Heart failure
  • Renal disease
  • Hepatic disease
  • Signs or symptoms of hypernatremia (anorexia, nausea or vomiting, altered mental status [lethargy, irritability, stupor, coma], musculoskeletal symptoms [twitching, hyperreflexia, ataxia])
  • Signs or symptoms of hyponatremia (anorexia, nausea or vomiting, altered mental status [difficulty concentrating, confusion, lethargy, agitation], headache, seizures)

Considerations

Drugs that can increase serum sodium include the following:

  • Anabolic steroids
  • Oral contraceptives
  • Certain antibiotics
  • Clonidine
  • Corticosteroids
  • Laxatives
  • Lithium
  • Nonsteroidal anti-inflammatory drugs (NSAIDs)

Drugs that can decrease serum sodium include the following:

  • Carbamazepine
  • Diuretics
  • Morphine
  • Sulfonylureas
  • Triamterene
  • Vasopressin
  • Clofibrate
  • Vincristine [2]
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