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Phosphorus (Serum) 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 is involved in energy production.

Quick summary

["Your blood phosphorus levels can help doctors assess bone health and metabolic function."]

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

Key facts at a glance

LOINC
14406-3
Short code
Phosphate Snv-mCnc
Synonyms
Phosphate Snv-mCnc
Category
electrolyte
Sample
fluid
Container
Sterile tube
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
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like muscle weakness, fatigue, or bone pain. It could also be part of a routine check-up or evaluation for conditions like kidney disease, diabetes, 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 isn’t always required for phosphorus alone. Bring any medications you’re taking to your appointment.

How the Test Is Performed

A blood sample is drawn from a vein, usually in your arm, by a healthcare professional. The blood is sent to a lab for analysis. Phosphorus levels are measured using a chemical method that detects its presence in the serum.

What the Results Mean

Results are typically reported as a mass concentration (e.g., mg/dL or mmol/L). While reference ranges vary by lab, low or high levels may signal underlying health concerns that need further investigation.

Reference range

Adult: 2.5-4.5 mg/dLN/A

Specimen: fluid

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.

Low phosphorus levels (hypophosphatemia) can cause muscle weakness, bone pain, or even seizures in severe cases. High phosphorus levels (hyperphosphatemia) may indicate kidney problems, metabolic imbalances, or certain cancers. Your provider will interpret results in the context of your overall health and symptoms.

Short name

Serum Phosphorus

Frequently asked questions

What causes low phosphorus levels?
Low phosphorus can result from poor diet (low intake of foods like nuts, seeds, or dairy), kidney disease (which fails to regulate phosphorus), excessive sweating, or certain medications (e.g., antacids).
What causes high phosphorus levels?
High phosphorus is often linked to kidney failure, excessive vitamin D intake, or certain cancers. It can also occur from overuse of phosphate-containing laxatives or supplements.
How often should I get this test?
Your provider will determine how often you need this test based on your health status, symptoms, or ongoing conditions. Regular monitoring may be recommended if you have chronic kidney disease, diabetes, or other metabolic disorders.
  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