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Phosphorus (Serum/Plasma) Concentration

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

This test measures the amount of phosphorus, a mineral essential for healthy bones and cells, in your blood.

Quick summary

["Phosphorus levels help assess bone health and kidney function."]

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

Key facts at a glance

LOINC
35222-9
Short code
Phosphate Ur-msCnc
Synonyms
Phosphate Ur-msCnc
Category
electrolyte
Sample
urine
Container
Sterile urine container
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
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to check for conditions affecting phosphorus balance, such as kidney disease, metabolic bone disorders, or certain medications that alter phosphorus levels. It can also be part of routine monitoring for patients with chronic conditions like diabetes or heart disease.

What Does the Result Mean?

Results may be low or high depending on underlying health issues. Low levels could signal kidney problems, malnutrition, or overuse of certain medications. High levels might indicate kidney disease, overactive parathyroid gland, or certain cancers.

Common Conditions Monitored

This test is often used to monitor patients with chronic kidney disease, those on long-term medications like phosphate binders, or individuals with conditions like hypoparathyroidism or hyperparathyroidism.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where it is processed to separate serum or plasma for testing. Phosphorus levels are measured using a specialized laboratory technique.

Reference range

Adult: 2.5-4.5 mg/dLN/A

Specimen: urine

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 My Next Steps If My Result Is Abnormal?
If your phosphorus level is outside the expected range, your doctor may recommend further tests, such as additional blood tests (e.g., calcium, parathyroid hormone), imaging studies, or a review of your medications and diet. Follow-up visits will help determine the best course of action based on your specific health needs.
How Often Should I Get This Test?
The frequency depends on your health condition and treatment plan. Your doctor will advise you on how often to get this test, especially if you have chronic kidney disease, are on phosphate binders, or have other conditions that affect phosphorus levels.
Can I Prepare for This Test?
No special preparation is needed for this test. However, inform your doctor about any medications you’re taking, including over-the-counter supplements, as they may affect results. Avoiding certain foods or drinks (like those high in phosphorus) before the test isn’t typically required unless instructed by your healthcare provider.
  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