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Phosphorus (Serum) Concentration

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of phosphorus, an essential mineral, in your blood serum. Phosphorus works with calcium to maintain strong bones and healthy teeth, and it plays a role in energy production and cell function.

Quick summary

["Your blood phosphorus levels help assess mineral balance and kidney function."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
55972-4
Short code
Phosphate p dialysis SerPl-sCnc
Synonyms
Phosphate p dialysis SerPl-sCnc
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
2.5
Ref high
4.5
Critical range
1 N/A – —
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84100
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may order this test if you have symptoms like muscle weakness, bone pain, or fatigue, or if you have conditions such as kidney disease, diabetes, or certain metabolic disorders. It may also be checked during routine health evaluations or before certain treatments.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if instructed, but this is not always required. Bring any medications you’re currently taking to your appointment.

How the Test Is Performed

A blood sample is drawn from a vein, typically in your arm, by a healthcare professional. The blood is then sent to a lab for analysis to determine phosphorus concentration.

What the Results Mean

Results are reported as a mass concentration (typically in mg/dL or mmol/L). High or low levels can indicate underlying health issues, such as kidney problems, hormonal imbalances, or other conditions. Your provider will interpret the results in the context of your overall health.

Reference range

Adult: 2.5-4.5 mg/dLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Serum Phosphorus

Frequently asked questions

What Are Common Causes of Abnormal Results?
High phosphorus levels (hyperphosphatemia) may be caused by kidney disease, certain medications (like phosphate-containing supplements), or conditions that lead to low calcium levels. Low phosphorus levels (hypophosphatemia) can result from malnutrition, excessive sweating, or conditions affecting bone metabolism.
How Might My Results Affect My Treatment?
Your provider will use these results to guide treatment, such as adjusting medications, dietary changes, or managing conditions like kidney disease. They may also recommend follow-up tests if needed to monitor phosphorus levels over time.
Can I Check My Phosphorus Levels at Home?
No, phosphorus levels are typically checked in a clinical lab setting. Over-the-counter tests for blood minerals are not reliable for accurate results and should not replace professional medical evaluation.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy