Phosphorus (Inorganic Phosphate)

Cleveland Heartlab P, Test

CPT Code: 84100
Order Code: C116
ABN Requirement:  No
Synonyms: PO₄; Inorganic Phosphate
Specimen: Serum
Volume: Serum: 0.5 mL
Minimum Volume: Serum: 0.2 mL
Container: Gel-barrier tube (SST, Tiger Top)


  1. Collect and label sample according to standard protocols.
  2. Gently invert tube 5 times immediately after draw. DO NOT SHAKE.
  3. Allow blood to clot 30 minutes.
  4. Centrifuge for 10 minutes.

Patient Preparation: Fasting may be required for this test. Please ask your doctor if you should fast prior to testing.

Transport: Store serum at 2°C to 8°C after collection and ship the same day per packaging instructions included with the provided shipping box.


Ambient (15-25°C): 24 hours
Refrigerated (2-8°C): 7 days
Frozen (-20°C): 1 year

Causes of Rejection: Specimens other than serum; improper labeling; samples not stored properly; samples older than stability limits; moderately or grossly hemolyzed specimens

Methodology: Photometric

Turn Around Time: 1 to 3 days

Reference Range:

Age mg/dL
0-2 years 4.2-7.0
3-8 years 3.3-6.5
9-12 years 3.0-6.1
13-16 years 2.5-5.0
≥17 years 2.5-4.5

Priority Value:

Age Priority 1 Value (mg/dL)
All Ages ≤1.0

Clinical Significance:
Serum phosphorus (Phosphate) levels alone are of limited diagnostic value and should be correlated with serum calcium levels. An increased phosphorus with decreased calcium suggests either hypoparathyroidism or renal disease. A decreased phosphorus and an increased calcium suggests hyperparathyroidism or sarcoidosis. When both calcium and phosphorus are decreased diagnostic considerations include malabsorption, vitamin D deficiency and renal tubular acidosis. Increased phosphorus and normal or increased calcium suggests Milk-alkali syndrome or hypervitaminosis D.

Limitations: Moderate to gross hemolysis may adversely affect results. Phospholipids contained in liposomal drug formulations (e.g. AmBisome) may be hydrolyzed during testing, and may lead to elevated phosphate results. In very rare cases gammopathy may cause unreliable results.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.