Potassium, Blood and Potassium, Urine

General

Core Lab Study

Synonym/Acronym:
Serum and urine K+.

Rationale
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.

A small group of studies in this Manual have been identified as Core Lab Studies. The designation is meant to assist the reader in sorting the basic “always need to know” laboratory studies from the hundreds of other valuable studies found in the Manual—a way to begin putting it all together.

Normal, abnormal, or various combinations of core lab study results can indicate that all is well, reveal a problem that requires further investigation with additional testing, signal a positive response to treatment, or suggest that the health status is as expected for the associated situation and time frame.

Potassium, an essential mineral and electrolyte, is a frequently requested study and is included in the Electrolyte panel, Comprehensive Metabolic panel (CMP), General Health panel, and Hypertension panel. Panels are used as general health and targeted screens to identify or monitor conditions such as bone disease, diabetes, hypertension, kidney disease, liver disease, or malnutrition.

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 blood specimen collection. Urine from an unpreserved random or timed specimen is collected in a clean plastic collection container. As appropriate, provide the required urine collection container and specimen collection instructions.

Normal Findings
Method: Ion-selective electrode.


Blood
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.

Urine
AgeConventional UnitsSI Units (Conventional Units × 1)
6–10 yr
  Male17–54 mEq/24 hr or mmol/24 hr17–54 mmol/24 hr
  Female8–37 mEq/24 hr or mmol/24 hr8–37 mmol/24 hr
10–14 yr18–58 mEq/24 hr or mmol/24 hr18–58 mmol/24 hr
Adult–older adult26–123 mEq/24 hr or mmol/24 hr26–123 mmol/24 hr
Note: Reference values depend on potassium intake and diurnal variation. Excretion is significantly higher at night.Potassium excretion declines in older adults 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

Blood: Adults and Children

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

Blood: Newborns

  • Hypokalemia Less than 2.8 mEq/L or mmol/L (SI: Less than 2.8 mmol/L)
  • Hyperkalemia 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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