Order Code
2227
Preferred Specimen
Collect 2 mL of serum. Allow the SST tube to clot upright for at least 30 minutes, then centrifuge within 2 hours after collection. Keep sample refrigerated.
Container Type
Serum separator tube
Alternate Specimen Requirements
If needed, collect 2 mL of serum using a plain red top tube. Allow it to clot in an upright position for at least 60 minutes, then centrifuge and transfer the serum to a plastic transport tube within 2 hours. Clearly label the tube as “serum from plain red top tube.” Keep refrigerated.
Minimum Volume
- Adult: 1 mL serum
- Pediatric: 0.2 mL serum (Note: does not allow for repeat or additional testing.)
Transport Temperature
Refrigerated
Expected Turnaround Time
1 day
Specimen Stability
- Room temperature: 1 day
- Refrigerated: 1 week
- Frozen: 1 year
Methodology
Roche COBAS UV assay (molybdate)
Rejection Criteria:
- Moderate or greater hemolysis
Overview
Phosphorus, often referred to as phosphate (phosphorus combined with four oxygen atoms), is the most common intracellular anion in the body. It plays a key role in cell membrane structure, energy storage (ATP), cellular transport, and is an essential component of DNA and RNA.
Around 85% of phosphorus resides in the bones and teeth, about 15% in soft tissues (mostly skeletal muscle), and only 0.1% circulates in the serum or plasma, which is the portion measured during testing.
Phosphorus and calcium metabolism are closely linked and regulated by the parathyroid hormone—their blood levels typically move in opposite directions. Abnormal phosphorus levels often suggest an accompanying calcium imbalance. Since phosphorus is absorbed through the intestines and excreted via the kidneys, renal dysfunction is a leading cause of elevated phosphorus levels.
Clinical Significance
- Ongoing management of chronic kidney disease (CKD)
- Evaluation of hyperparathyroidism
- Assessment of poor growth, impaired bone or tooth development
- Investigation of nonspecific symptoms such as:
- Loss of appetite
- Bone pain or stiffness
- Fatigue and irritability
- Numbness or muscle weakness
Additional Information
Phosphorus is essential for cell growth, repair, and energy utilization. Symptoms from low or high phosphorus levels are usually seen only in severe cases.
- Low phosphorus (hypophosphatemia) can cause weakness in skeletal and smooth muscles, respiratory issues, eye muscle paralysis, or intestinal blockage (ileus). In extreme cases, it may lead to rhabdomyolysis.
- High phosphorus (hyperphosphatemia) often causes no symptoms, but can result in bone disease (from secondary hyperparathyroidism) or soft tissue calcification.
Renal problems are the most common cause of high phosphorus. In CKD, phosphorus and calcium levels are monitored closely, with management often involving diet changes, phosphate binders, or vitamin D supplements. Maintaining proper phosphorus balance helps prevent parathyroid issues and reduces complications and mortality (KDOQI 2009).
Routine phosphorus checks are also advised for patients at risk of malnutrition, renal disease, alcohol abuse, or those taking diuretics.
Interpretative Information
Causes of Low Phosphorus (Hypophosphatemia):
- Renal phosphate wasting
- Shift of phosphate into cells
- Gastrointestinal phosphate loss
- Hyperparathyroidism
- Hypercalcemia
- Malabsorption or malnutrition
- Alcoholism
- Vitamin D deficiency
- Respiratory alkalosis
- Severe burns
- Refeeding syndrome
- Certain medications (e.g., diuretics, antacids)
Causes of High Phosphorus (Hyperphosphatemia):
- Reduced kidney excretion of phosphate
- Hypoparathyroidism
- Hypocalcemia
- Renal disease
- Diabetic ketoacidosis
- Vitamin D excess
- Hemolysis or rhabdomyolysis
- Phosphorus-containing laxatives
Limitations
Falsely elevated phosphorus results may occur with:
- Hyperbilirubinemia
- Dysproteinemia
- Hypertriglyceridemia
- Multiple myeloma
- Use of glassware contaminated with detergents
Certain drugs can also alter phosphorus levels:
- Decrease levels: alcohol, insulin, bile acid sequestrants, ACE inhibitors, cyclosporine, antacids
- Increase levels: corticosteroids (UMMS 2013)
References
Bakker AJ, Bosma H, Christen PJ. Ann Clin Biochem. 1990;27(Pt 3):227–231.
Bourke E, Yanagawa M. Clin Lab Med. 1993;13(1):183–207.
Delmez JA, Slatopolsky E. Am J Kidney Dis. 1992;19(4):303–317.
Elliott P, Kesteloot H, Appel LJ, et al. Hypertension. 2008;51(3):669–675.
Halevy J, Bulvik S. Arch Intern Med. 1988;148(1):153–155.
Heaney RP, Nordin BE. J Am Coll Nutr. 2002;21(3):239–244.
KDIGO CKD-MBD Work Group. Kidney Int. 2009;76(Suppl113):S1–S130.
Lobaugh B, Neelon FA, Oyama H, et al. Surgery. 1989;106(6):1009–1016.
Mehanna H, Nankivell PC, Moledina J, et al. Head Neck Oncol. 2009;1:4.
Portale AA, Halloran BP, Morris RC Jr. J Clin Invest. 1987;80(4):1147–1154.
Subramanian R, Khardori R. Medicine. 2000;79(1):1–8.
University of Maryland Medical Center. Phosphorus. 2013. umm.edu/health/medical/altmed/supplement/phosphorus
U.S. Department of Health & Human Services. Dietary Guidelines for Americans. 2005.
Test Setup Days
Monday through Friday PM shift
CPT
84100 LOINC: 2777-1
Reference Range
MALE: AGE 0-1 MONTH: 3.6-6.9 MG/DL
2 MONTHS-1 YEAR: 3.5-6.6 MG/DL
2-3 YEARS: 3.1-6.0 MG/DL
4-6 YEARS: 3.3-5.6 MG/DL
7-9 YEARS: 3.0-5.4 MG/DL
10-12 YEARS: 3.2-5.7 MG/DL
13-15 YEARS: 2.9-5.1 MG/DL
16-18 YEARS: 2.7-4.9 MG/DL
>18 YEARS: 2.5-4.5 MG/DL
FEMALE: AGE 0-1 MONTH: 4.3-7.7 MG/DL
2 MONTHS-1 YEAR: 3.7-6.5 MG/DL
2-3 YEARS: 3.4-6.0 MG/DL
4-6 YEARS: 3.2-5.5 MG/DL
7-9 YEARS: 3.1-5.5 MG/DL
10-12 YEARS: 3.3-5.3 MG/DL
13-15 YEARS: 2.8-4.8 MG/DL
16-18 YEARS: 2.5-4.8 MG/DL
>18 YEARS: 2.5-4.5 MG/DL
| UNIT CODE | UNIT CODE NAME | ANALYTE | GENDER | AGE | REFERENCE RANGE | Units of Measure |
|---|---|---|---|---|---|---|
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 0Y | 2.5-4.5 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 1M | 3.6-7.7 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 1Y | 3.5-6.6 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 3Y | 3.1-6.0 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 6Y | 3.2-5.6 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 9Y | 3.0-5.5 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 12Y | 3.2-5.7 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 15Y | 2.8-5.1 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 18Y | 2.5-4.9 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | NOT SPECIFIED | 150Y | 2.5-4.5 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 0Y | 2.5-4.5 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 1M | 3.6-6.9 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 1Y | 3.5-6.6 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 3Y | 3.1-6.0 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 6Y | 3.3-5.6 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 9Y | 3.0-5.4 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 12Y | 3.2-5.7 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 15Y | 2.9-5.1 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 18Y | 2.7-4.9 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | MALE | 150Y | 2.5-4.5 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 0Y | 2.5-4.5 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 1M | 4.3-7.7 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 1Y | 3.7-6.5 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 3Y | 3.4-6.0 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 6Y | 3.2-5.5 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 9Y | 3.1-5.5 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 12Y | 3.3-5.3 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 15Y | 2.8-4.8 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 18Y | 2.5-4.8 | MG/DL |
| 2227 | PHOSPHORUS | PHOS | FEMALE | 150Y | 2.5-4.5 | MG/DL |