Lab Test

Potassium, Serum


Test Codes

Antrim #15770, EPIC: LAB5101, SOFT: K


Note: Blood should be obtained with as little venous stasis (i.e. tourniquet time) as possible. Fist clenching may result in false elevation of potassium.

Specimen Collection Criteria

Collect: One Gold-top SST tube. (Minimum Whole Blood: 4.0 mL)

Contact Laboratory for acceptability of other tube types.
See Minimum Pediatric Specimen Requirements for Microtainer® collection.

Caution: Never refrigerate collection tube prior to centrifugation. This may cause a falsely elevated potassium. 

Physician Office/Draw Specimen Preparation

Let SST specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged SST tube within two hours of collection. (Minimum: 0.5 mL)

Preparation for Courier Transport

Transport: Centrifuged SST tube, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL)

Rejection Criteria

  • Moderate to grossly hemolyzed specimens.
  • Inadequately centrifuged Microtainers® or Gold-top tubes.
  • Red-top tubes with serum not separated from cells within two hours of collection.

In-Lab Processing

Let SST specimens clot 30-60 minutes. Centrifuge SST tubes or Microtainers® to separate serum from cells. Deliver immediately to the appropriate testing station.


Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers® with Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers® without Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 7 days

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days


Farmington Hills Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory
Troy Chemistry Laboratory


Sunday – Saturday, 24 hours a day.
STAT results available within 1 hour of receipt in the Laboratory.
Routine results available within 4 hours.

Reference Range

Adult range: 3.5 - 5.2 mmol/L.

Age related reference range:

Age  Range (mmol/L)
0 – 1 day 5.0 – 7.5
2 days – 3 months 4.0 – 6.0
4 months – adult 3.5 – 5.2

Breast Milk
(15 days to 15 months post partum): 8.7-17.5 mmol/L.

Test Methodology



  • Spuriously increased levels may be seen:
    • Following excessive hand clenching prior to phlebotomy.
    • If the needle (or Vacutainer®) has been inserted into an EDTA tube prior to the tube used for potassium analysis.
    • If whole blood sample is refrigerated prior to separation of serum from red cells.
    • In a hemolyzed sample.
    • With significantly increased platelet or leukocyte counts if serum is used.
  • Hyperkalemia (increased potassium): May occur in a number of conditions including renal failure, adrenal insufficiency, acidosis, malignant hyperthermia and with use of potassium-sparing diuretics.
  • Hypokalemia (decreased potassium): May be seen in primary hyperaldosteronism, Cushing's syndrome, vomiting, diarrhea, and in patients on diuretics (potassium-losing) or with severe burns.

Clinical Utility

  • The quantitation of potassium is used to monitor electrolyte balance.
  • Pseudohyperkalemia: If an increase in platelets or leukocytes is suspected as a cause of hyperkalemia, a heparin tube should be obtained for plasma potassium.  

CPT Codes



Last Updated


Microtainer® and Vacutainer® are registered trademarks of Becton, Dickinson and Company.
UroVysion® is a registered trademark of Abbott Laboratories. ThinPrep® is a registered trademark of Hologic, Incorporated.


This directory currently reflects information only for specimens collected and/or processed at the
Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.