Sodium, Blood

Sodium, Blood

Synonym/acronym: Serum Na+.

Common use

To assess electrolyte balance related to hydration levels and disorders such as diarrhea and vomiting and to monitor the effect of diuretic use.


Serum (1 mL) collected in a gold-, red-, or red/gray-top tube. Plasma (1 mL) collected in a green-top (heparin) tube is also acceptable.

Normal findings

(Method: Ion-selective electrode)
AgeConventional & SI Units
Cord126–166 mEq/L or mmol/L
1–12 hr124–156 mEq/L or mmol/L
12–24 hr132–159 mEq/L or mmol/L
24–48 hr134–160 mEq/L or mmol/L
48–72 hr139–162 mEq/L or mmol/L
Newborn135–145 mEq/L or mmol/L
7 d–1 mo134–144 mEq/L or mmol/L
2 mo–5 mo134–142 mEq/L or mmol/L
6 mo–1 yr133–142 mEq/L or mmol/L
Child-Adult–older adult135–145 mEq/L or mmol/L
Note: Older adults are at increased risk for both hypernatremia and hyponatremia. Diminished thirst, illness, and lack of mobility are common causes for hypernatremia in older adults. There are multiple causes of hyponatremia in older adults, but the most common factor may be related to the use of thiazide diuretics.


Electrolytes dissociate into electrically charged ions when dissolved. Cations, including sodium, carry a positive charge. Body fluids contain approximately equal numbers of anions and cations, although the nature of the ions and their mobility differs between the intracellular and extracellular compartments. Both types of ions affect the electrical and osmolar functions of the body. Electrolyte quantities and the balance among them are controlled by oxygen and carbon dioxide exchange in the lungs; absorption, secretion, and excretion of many substances by the kidneys; and secretion of regulatory hormones by the endocrine glands. Sodium is the most abundant extracellular cation that together with chloride and bicarbonate participate in a number of essential functions to include maintaining the osmotic pressure of extracellular fluid, regulating renal retention and excretion of water, maintaining acid-base balance, regulating potassium levels, stimulating neuromuscular reactions, and maintaining systemic blood pressure. Hypernatremia (elevated sodium level) occurs when there is excessive water loss or abnormal retention of sodium. Hyponatremia (low sodium level) occurs when there is inadequate sodium retention or inadequate intake.

This procedure is contraindicated for



  • Determine whole-body stores of sodium, because the ion is predominantly extracellular
  • Monitor the effectiveness of drug therapy, especially diuretics, on serum sodium levels

Potential diagnosis

Increased in

  • Azotemia (related to increased renal retention)
  • Burns (hemoconcentration related to excessive loss of free water)
  • Cushing’s disease
  • Dehydration
  • Diabetes (dehydration related to frequent urination)
  • Diarrhea (related to water loss in excess of salt loss)
  • Excessive intake
  • Excessive saline therapy (related to administration of IV fluids)
  • Excessive sweating (related to loss of free water, which can cause hemoconcentration)
  • Fever (related to loss of free water through sweating)
  • Hyperaldosteronism (related to excessive production of aldosterone, which increases renal absorption of sodium and increases blood levels)
  • Lactic acidosis (related to diabetes)
  • Nasogastric feeding with inadequate fluid (related to dehydration and hemoconcentration)
  • Vomiting (related to dehydration)

Decreased in

    Central nervous system disease Congestive heart failure (diminished renal blood flow due to reduced cardiac capacity decreases urinary excretion and increases blood sodium levels) Cystic fibrosis (related to loss from chronic diarrhea; poor intestinal absorption) Excessive antidiuretic hormone production (related to excessive loss through renal excretion) Excessive use of diuretics (related to excessive loss through renal excretion; renal absorption is blocked) Hepatic failure (hemodilution related to fluid retention) Hypoproteinemia (related to fluid retention) Insufficient intake IV glucose infusion (hypertonic glucose draws water into extracellular fluid and sodium is diluted) Mineralocorticoid deficiency (Addison’s disease) (related to inadequate production of aldosterone, which results in decreased absorption by the kidneys) Nephrotic syndrome (related to decreased ability of renal tubules to reabsorb sodium)

Critical findings

  • Hyponatremia: Less than 120 mEq/L or mmol/L (SI: Less than 120 mmol/L)
  • Hypernatremia: Greater than 160 mEq/L or mmol/L (SI: Greater than 160 mmol/L)
  • Consideration may be given to verifying the critical findings before action is taken. Policies vary among facilities and may include requesting immediate recollection and retesting by the laboratory or retesting using a rapid Point of Care instrument at the bedside.

  • Note and immediately report to the health-care provider (HCP) any critically increased or decreased values and related symptoms especially fluid imbalance.

  • It is essential that a critical finding be communicated immediately to the requesting health-care provider (HCP). A listing of these findings varies among facilities.

  • Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. Notification processes will vary among facilities. Upon receipt of the critical value the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, Hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical value, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.

  • Signs and symptoms of hyponatremia include confusion, irritability, convulsions, tachycardia, nausea, vomiting, and loss of consciousness. Possible interventions include maintenance of airway, monitoring for convulsions, fluid restriction, and performance of hourly neurological checks. Administration of saline for replacement requires close attention to serum and urine osmolality.

  • Signs and symptoms of hypernatremia include restlessness, intense thirst, weakness, swollen tongue, seizures, and coma. Possible interventions include treatment of the underlying cause of water loss or sodium excess, which includes sodium restriction and administration of diuretics combined with IV solutions of 5% dextrose in water (D5W).

Interfering factors

  • Drugs that may increase serum sodium levels include anabolic steroids, angiotensin, bicarbonate, carbenoxolone, cisplatin, corticotropin, cortisone, gamma globulin, and mannitol.
  • Drugs that may decrease serum sodium levels include amphotericin B, bicarbonate, cathartics (excessive use), chlorpropamide, chlorthalidone, diuretics, ethacrynic acid, fluoxetine, furosemide, laxatives (excessive use), methyclothiazide, metolazone, nicardipine, quinethazone, theophylline (IV infusion), thiazides, and triamterene.
  • Specimens should never be collected above an IV line because of the potential for dilution when the specimen and the IV solution combine in the collection container, falsely decreasing the result. There is also the potential of contaminating the sample with the substance of interest, if it is present in the IV solution, falsely increasing the result.

Nursing Implications and Procedure

Potential nursing problems

ProblemSigns & SymptomsInterventions
Fluid volume (Related to an excess or deficit of sodium associated with electrolyte disturbance and associated disease process)Deficient: decreased urinary output, fatigue, sunken eyes, dark urine, decreased blood pressure, increased heart rate, and altered mental status. Overload: edema, shortness of breath, increased weight, ascites, rales, rhonchi, and diluted laboratory valuesRecord daily weight and monitor trends; record accurate intake and output; collaborate with physician with administration of IV fluids to support hydration; monitor laboratory values that reflect alterations in fluid status (potassium, blood urea nitrogen, creatinine, calcium, hemoglobin, and hematocrit, sodium); manage underlying cause of fluid alteration; monitor urine characteristics and respiratory status; establish baseline assessment data; collaborate with physician to adjust oral and IV fluids to provide optimal hydration status; administer replacement electrolytes as ordered; adjust diuretics as appropriate
Electrolyte imbalance: Excess (Related to excess fluid loss, watery diarrhea; inability to take oral fluids; excess perspiration; large area burns; excess sodium intake)
Deficit (Related to excess sodium loss through kidneys; diuretic use; adrenal insufficiency with altered cortisol and aldosterone production; vomiting and diarrhea; heart failure; renal failure; cirrhosis)
Excess: furrowed tongue; dry mouth; headache; dry skin; seizures; coma; tachycardia; hypotension; vascular collapse; restlessness; increased urine; output; weight gain; altered mental status. Deficit: muscle cramps; weakness; fatigue; confusion; anorexia; nausea; vomiting; abdominal cramps; diarrhea; headache; depression; personality changes; irritability; muscle twitching; coma; anxietyCorrelate sodium imbalance with disease process, nutritional intake, renal function, medications; monitor ECG status; monitor for respiratory changes; minimize metabolic complications; provide a safe environment to prevent injury; collaborate with the pharmacist and HCP for appropriate pharmacologic interventions; adjust medication dosage to compensate for renal impairment; collaborate with dietician for dietary modifications; use renal dialysis as necessary; reduce or increase intake of high-sodium foods and salts; if deficit avoid thiazide diuretics; if excess use diuretics to increase sodium excretion; if excess use IV fluids to remedy dehydration; if excess use IV NACL infusion as prescribed
Diarrhea (Related to gastric irritation from diet or disease; stress; drug side effect; laxative abuse; malabsorption; alcohol abuse; chemotherapy; enteric infections)Abdominal pain; cramping; frequent stools that exceed three per day; watery stools; gastrointestinal urgency; hyperactive bowel soundsAssess bowel sounds; send stool for culture as ordered; assess for food intolerances that can irritate the gastrointestinal tract; review tolerance to dairy products; check for a history of gastrointestinal disease or surgery; ask about foreign travel; administer prescribed antidiarrheal; evaluate and replace lost fluids; consider dietary bulk
Confusion (Related to sodium excess or deficit secondary to metabolic alterations, disease process, or burns)Disorganized thinking, restlessness, irritability, altered concentration and attention span, changeable mental function over the day, hallucinationsTreat the medical condition; correlate confusion with the need to reverse altered electrolytes; evaluate medications; prevent falls and injury through appropriate use of postural support, bed alarm, or the restraints; consider pharmacological interventions; record accurate intake and output to assess fluid status


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in evaluating electrolyte balance.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s cardiovascular, endocrine, and genitourinary systems; symptoms; and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Nutritional Considerations: Evaluate the patient for signs and symptoms of dehydration. Decreased skin turgor, dry mouth, and multiple longitudinal furrows in the tongue are symptoms of dehydration. Dehydration is a significant and common finding in geriatric and other patients in whom renal function has deteriorated.
  • Nutritional Considerations: If appropriate, educate patients with low sodium levels that the major source of dietary sodium is found in table salt. Many foods, such as milk and other dairy products, are also good sources of dietary sodium. Most other dietary sodium is available through the consumption of processed foods. Patients on low-sodium diets should be advised to avoid beverages such as colas, ginger ale, sports drinks, lemon-lime sodas, and root beer. Many over-the-counter medications, including antacids, laxatives, analgesics, sedatives, and antitussives, contain significant amounts of sodium. The best advice is to emphasize the importance of reading all food, beverage, and medicine labels.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.
  • Patient Education

    • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP.
    • Recognize anxiety related to test results and answer any questions or address any concerns voiced by the patient or family.
    • Educate the patient regarding access to nutritional counseling services.
    • Provide contact information, if desired, for the Institute of Medicine of the National Academies (
    • Teach the patient and family to recognize symptoms of both an excess and deficit of sodium.
    • Teach the importance of fluid replacement with multiple diarrhea episodes.
  • Expected Patient Outcomes

    • Knowledge
    • States understanding that an altered sodium level can have a significant impact on cognitive function
    • States understanding that excessive watery stools can result in an altered sodium level
    • Skills
    • Identifies foods to select that will support a healthy sodium level
    • Selects dietary supplements to what is required to support a healthy sodium level
    • Attitude
    • Complies with the recommendation to monitor diarrhea and report excessive stools to the HCP
    • Complies with the recommendation to increase oral fluid intake to replace lost fluids that can affect sodium levels

Related Monographs

  • Related tests include ACTH, aldosterone, anion gap, ANP, BNP, blood gases, BUN, calculus kidney stone panel, BUN, calcium, carbon dioxide, chloride, chloride sweat, cortisol, creatinine, DHEAS, echocardiography, glucose, insulin, ketones, lactic acid, lung perfusion scan, magnesium, osmolality, potassium, renin, US abdomen, urine sodium, and UA.
  • Refer to the Cardiovascular, Endocrine, and Genitourinary systems tables at the end of the book for related tests by body system.
Full browser ?