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Sodium and Potassium, Urine

Urine Sodium and Potassium, Urine Sodium/K, Urine Na/K

Test Codes

EPIC: LAB5454, Beaker: NAKU, Antrim: 17125

Department

Chemistry

Instructions

Note: 24-hour and random urine specimens MUST be collected separately. See below for collection criteria.

• Please refer to the Specimen Collection Manual for instructions on 24-Hour or Random Urine Collection:
  • Urine 24-Hour Collection - Inpatient
  • Urine 24-Hour Collection - Outpatient
  • Urine 24-Hour Collection - Outreach
  • Random Urine Collection

Specimen Collection Criteria

Collect: 24-hour urine or timed urine specimen with a 24-hour urine container with no preservatives.
Also acceptable: Random urine specimen in a screw-capped container (preferred) or another sterile collection cup. Preservatives are not acceptable for random urine specimens. (Minimum: 20 mL)

• Refer to the table of Urine Preservative Options when multiple tests are requested.
• Keep 24-hour urine specimen iced or refrigerated during collection.
• Include start and end dates and times for the collection period on the specimen container.

Urine Preservative Options
No Preservative	6N Hydrochloric Acid	Boric Acid (10g)	Sodium Carbonate	50% Acetic Acid
Preferred	Acceptable	Acceptable	Unacceptable	Unacceptable

Physician Office/Draw Specimen Preparation

Maintain specimens refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Transport: Entire 24-hour urine collection, or random urine, refrigerated (2-8°C or 36-46°F).

Rejection Criteria

Specimens not collected and processed as indicated. 

In-Lab Processing

Measure total volume of 24-hour urine specimen. Record total volume and collection start and end dates and times in the LIS system. Aliquot a minimum of 10 mL from the well-mixed 24-hour urine collection.

Storage

Specimen Stability for Testing:

Room temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): For longer storage.

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days (Royal Oak and Troy store an aliquot for 30 days.)

Laboratory

Dearborn Chemistry Laboratory

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

Performed

Sunday – Saturday.
Results available within 24 hours.

Reference Range

Sodium:  40-220 mmol/24 hours.
Potassium:  25-125 mmol/24 hours.

Normal ranges for random urines or for collections other than 24 hours have not been established.

Test Methodology

Potentiometry.

Interpretation

• Urinary sodium levels less than 10 mmol/L are associated with extra-renal sodium loss (GI or sweat), pre-renal azotemia, severe volume depletion, and edematous states. Levels greater than 10 mmol/L are seen in acute tubular necrosis, SIADH, Addison's disease, and renal salt wasting.
• Urine potassium levels less than 20 mmol/L are associated with non-renal conditions, while levels greater than 20 mmol/L are usually due to renal causes. Potassium loss is likely to occur in primary aldosteronism.

Clinical Utility

• Urinary sodium measurements aid in the evaluation of patients with acute oliguria (low urine output), hyponatremia, and volume depletion.
• Urinary potassium measurements are used to monitor electrolyte balance in the diagnosis and treatment of disease conditions characterized by low or high blood potassium levels.

CPT Codes

84133, 84300.

Contacts

Last Updated

10/30/2023