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Serum Phosphorus (Phosphorus Level)

Published: August 9, 2026Updated: August 16, 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 16, 2026Editorial policy

Key facts at a glance

LOINC
49682-8
Short code
LPT PHA 3D Bld-Rto
Synonyms
LPT PHA 3D Bld-Rto
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85610
SNOMED
396252006
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for conditions affecting phosphorus balance, such as kidney disease (which can cause phosphorus to build up), vitamin D deficiency, or metabolic disorders. It may also be done to monitor treatment for conditions like hyperparathyroidism or certain cancers.

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 it’s part of a metabolic panel, but this is not always required. Bring any medications or supplements you’re taking to your appointment.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. The blood sample is sent to a lab for analysis. The test typically takes a few minutes, and you may feel slight discomfort or bruising afterward.

What the Results Mean

Results are compared to a standard range for healthy adults, but exact values can vary by lab. High or low phosphorus levels may signal underlying health issues that need further evaluation.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: whole-blood

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Phosphorus

Frequently asked questions

How often will I need this test?
This test may be repeated periodically if you have chronic conditions like kidney disease, diabetes, or are receiving treatments that affect phosphorus metabolism. Your provider will determine the timing based on your health needs.
What causes phosphorus levels to be too high or too low?
High phosphorus levels can result from kidney problems, certain medications (like phosphate salts), or metabolic disorders. Low levels may occur due to kidney dysfunction, vitamin D deficiency, or excessive loss through urine or diarrhea.
Can diet affect phosphorus test results?
Yes, phosphorus is found in many foods, including dairy, nuts, seeds, and processed foods. If your test is part of a metabolic panel, your provider may ask you to avoid high-phosphorus foods for a short time before testing to get a more accurate baseline.
  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 16, 2026. · Read our editorial policy