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 provided with the Cleveland HeartLab shipping box.


Ambient (15-25°C): 24 hours
Refrigerated (2-8°C): 7 days
Frozen (-20°C): 1 year
Deep Frozen (-70°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

Critical Value:

Age Critical Value mg/dL
All Ages ≤1.0

Intended Use:
Phosphate testing is indicated for individuals with uncontrolled diabetes or kidney disorder, and is often used as a follow-up to an abnormal calcium level or when an individual displays symptoms of abnormal calcium levels. It is also used to monitor the efficacy of calcium or phosphate supplementation.

Limitations: Moderate to gross hemolysis may adversely affect results. Phospholipids contained in liposomal drug formulations (e.g. AmBisome) may be hydrolyzed during testing, thus 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.