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Phosphorus (Serum) Concentration

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

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

Quick summary

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

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

Key facts at a glance

LOINC
5994-9
Short code
PA PRP Ca Ionoph
Synonyms
PA PRP Ca Ionoph
Category
hematology
Sample
plasma
Container
Lavender-top (EDTA) or Green-top (Heparin)
Units
N/A
Ref low
7.35
Ref high
7.45
Critical range
7.2 N/A – 7.6 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
aggregometry-calcium-ionophore-induced
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 Is This Test Done?

Your doctor may order this test to evaluate kidney function, monitor treatment for conditions like hypophosphatemia or hyperphosphatemia, or check for metabolic bone diseases. It can also help diagnose or manage conditions affecting phosphorus balance, such as malnutrition or certain cancers.

What to Expect Before the Test

No special preparation is typically needed. You may be asked to fast for 8–12 hours before the test if it’s part of a metabolic panel, but always follow your healthcare provider’s instructions.

How the Test Is Performed

A blood sample is drawn from a vein, usually in your arm, by a healthcare professional. The sample is sent to a lab for analysis.

What the Results Mean

Results are compared to standard reference ranges, but exact values can vary by lab. Abnormal levels may signal underlying health concerns that require further evaluation.

Reference range

NCBI: pH 7.35-7.45N/A

Specimen: plasma

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.

◆Associated findings1

Short name

Serum Phosphorus

Frequently asked questions

What Are Common Causes of Abnormal Results?
Low phosphorus levels (hypophosphatemia) can result from conditions like malnutrition, kidney disease, or excessive vitamin D intake. High levels (hyperphosphatemia) may occur with kidney failure, certain medications, or metabolic disorders.
How Might My Doctor Use These Results?
Your doctor may adjust treatments, such as dietary changes or medications, if phosphorus levels are out of balance. They may also recommend additional tests to investigate the cause of abnormal results.
What Should I Do If My Test Results Are Abnormal?
Follow your doctor’s guidance for next steps. If you have symptoms like muscle weakness, bone pain, or fatigue, report them to your healthcare provider promptly.
  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