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Phosphorus in Serum (or Plasma)

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.

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
52122-9
Short code
PT p hep neut PPP
Synonyms
PT p hep neut PPP
Category
chemistry
Sample
plasma
Container
Lavender-top (EDTA) or Green-top (Heparin)
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
Method
coag-tissue-factor-induced-post-heparin-neutralization
CPT
85610
SNOMED
396252006
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 check for conditions affecting bone metabolism, kidney function, or hormonal imbalances. It can also help diagnose or monitor diseases like hyperparathyroidism, kidney disease, or metabolic disorders.

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 depends on your doctor’s instructions. Bring any medications you’re taking.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but it’s quick and painless. The blood sample is sent to a lab for analysis.

What the Results Mean

Results are compared to a reference range specific to your age, sex, and overall health. Low or high levels can signal underlying issues, but your doctor will interpret them in the context of your medical history and other tests.

Reference range

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

Specimen: plasma

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

Serum Phosphorus

Frequently asked questions

How often will I need this test?
This test is often done as part of a routine checkup, when symptoms like fatigue, muscle weakness, or bone pain appear, or when kidney function or bone health is suspected. Your doctor will determine how often it’s needed based on your health needs.
What are the normal reference ranges?
Reference ranges vary by lab and individual factors. Typical ranges for adults are often between 2.5 and 4.5 mg/dL (or mmol/L), but your doctor will provide your specific results.
Can I eat or drink before this test?
Follow your doctor’s instructions. Some tests require fasting, while others do not. Always confirm with your healthcare provider before the test.
  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