Potassium, Blood

Potassium, Blood is a topic covered in the Davis's Lab & Diagnostic Tests.

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Serum K+.

To evaluate fluid and electrolyte balance related to potassium levels toward diagnosing disorders such as acidosis, acute kidney injury, chronic kidney disease, and dehydration and to monitor the effectiveness of therapeutic interventions.

Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction. Instruct the patient not to clench and unclench the fist immediately before or during specimen collection.

Normal Findings
Method: Ion-selective electrode.

Serum PotassiumConventional and SI Units
Newborn3.2–5.5 mEq/L or mmol/L
7–29 days3.4–6 mEq/L or mmol/L
1–5 mo3.5–5.6 mEq/L or mmol/L
6–12 mo3.5–6.1 mEq/L or mmol/L
Child–18 yr3.8–5.1 mEq/L or mmol/L
Adult–older adult3.5–5.3 mEq/L or mmol/L
Anion GapConventional and SI Units
Child or adult8–16 mmol/L
Note: Value ranges may vary depending on the laboratory. Serum values are 0.1 mmol/L higher than plasma values, and reference ranges should be adjusted accordingly. It is important that serial measurements be collected using the same type of collection container to reduce variability of results from collection to collection.Older adults are at risk for hyperkalemia due to the decline in aldosterone levels, decline in kidney function, and effects of commonly prescribed medications that inhibit the renin-angiotensin-aldosterone system.

Critical Findings and Potential Interventions

Adults and Children

  • Less than 2.5 mEq/L or mmol/L (SI: Less than 2.5 mmol/L)
  • Greater than 6.2 mEq/L or mmol/L (SI: Greater than 6.2 or mmol/L)


  • Less than 2.8 mEq/L or mmol/L (SI: Less than 2.8 mmol/L)
  • Greater than 7.6 mEq/L or mmol/L (SI: Greater than 7.6 mmol/L)

Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.

Consideration may be given to verification of 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 testing instrument at the bedside, if available.

Symptoms of hyperkalemia include irritability, diarrhea, cramps, oliguria, difficulty speaking, and cardiac dysrhythmias (peaked T waves and ventricular fibrillation). Continuous cardiac monitoring is indicated. Administration of sodium bicarbonate or calcium chloride may be requested. If the patient is receiving an IV supplement, verify that the patient is voiding.

Symptoms of hypokalemia include malaise, thirst, polyuria, anorexia, weak pulse, low blood pressure, vomiting, decreased reflexes, and electrocardiographic changes (depressed T waves and ventricular ectopy). Replacement therapy is indicated.

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