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Phosphorus in Serum (Mass Concentration)

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

This test measures the amount of phosphorus, an essential mineral, in your blood serum. Phosphorus helps maintain healthy bones, teeth, and cells, and plays a role in energy production.

Quick summary

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

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

Key facts at a glance

LOINC
59037-2
Short code
Phosphate DiafP-mCnc
Synonyms
Phosphate DiafP-mCnc
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
SNOMED
394971007
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?

Doctors may order a serum phosphorus test to check for conditions affecting bone health, kidney function, or metabolic balance. It’s often used alongside other tests to diagnose or monitor diseases like kidney disease, diabetes, or certain 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 involves drawing blood from a vein. Avoid taking certain medications (like phosphate supplements) that day, as instructed by your healthcare provider.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm to draw blood. The process is quick and typically painless. The blood sample is then sent to a lab for analysis.

What Do Results Mean?

Results are compared to standard reference ranges, but exact values can vary by lab. High or low phosphorus levels may signal underlying health issues, such as kidney problems or hormonal imbalances.

Reference range

Adult: 2.5-4.5 mg/dLN/A

Specimen: serum

No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Phosphorus

Frequently asked questions

Why might my doctor ask for this test?
Your doctor may recommend this test if you have symptoms like fatigue, muscle weakness, bone pain, or if they suspect kidney disease, metabolic disorders, or conditions affecting phosphorus metabolism.
What are common symptoms linked to abnormal phosphorus levels?
Symptoms of low phosphorus may include muscle cramps, weakness, bone pain, or irregular heartbeat. High phosphorus levels might cause fatigue, nausea, or kidney problems. However, symptoms can vary widely and may not appear at all.
How often should I expect this test?
The frequency depends on your health status. Some people need this test regularly if they have chronic conditions like kidney disease, while others may only need it once for diagnostic purposes.
  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