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Phosphorus (Serum) Concentration

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

This test measures the amount of phosphorus, an essential mineral, present in your blood serum. Phosphorus helps maintain healthy bones, teeth, and cells, and works with calcium to support normal muscle and nerve function.

Quick summary

["Blood phosphorus levels help assess mineral balance and potential metabolic or bone disorders."]

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

Key facts at a glance

LOINC
14405-5
Short code
Phosphate Prt-mCnc
Synonyms
Phosphate Prt-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
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 This Test Might Be Ordered

Your doctor may recommend this test if you have symptoms like muscle weakness, bone pain, or abnormal kidney function. It can also be part of routine monitoring for conditions like chronic kidney disease or metabolic bone diseases.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a metabolic panel. Bring any medications you’re currently taking to your appointment.

How the Test Works

A blood sample is drawn from a vein in your arm. The sample is sent to a lab where it is analyzed to measure phosphorus concentration using a specialized chemical method.

What the Results Mean

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

Reference range

Adult: 2.5-4.5 mg/dLN/A

Specimen: serum

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 Phosphate

Frequently asked questions

What causes low phosphorus levels?
Low phosphorus levels can result from poor diet (low intake of foods like dairy, nuts, or legumes), excessive vomiting or diarrhea, kidney problems, or certain medications.
What causes high phosphorus levels?
High phosphorus levels may be linked to kidney disease, overuse of phosphate supplements, or certain cancers or medications that affect mineral balance.
Can diet affect phosphorus test results?
Yes, dietary intake of phosphorus-rich foods can temporarily influence results. If your test is part of a routine check, your doctor may advise fasting to avoid interference.
  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