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Phosphorus (Serum) Concentration

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

This test measures the amount of phosphorus, a mineral essential for healthy bones and cells, in your blood serum. Phosphorus helps maintain normal levels of calcium and phosphate in your body.

Quick summary

["Phosphorus levels can indicate bone health, kidney function, or metabolic balance."]

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

Key facts at a glance

LOINC
10884-5
Short code
Phosphate Stl-mCnt
Synonyms
Phosphate Stl-mCnt
Category
electrolyte
Sample
stool
Container
Clean container
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 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to check for conditions affecting phosphorus metabolism, such as kidney disease (which can cause phosphorus levels to rise), bone disorders, or metabolic disorders like diabetes or hyperparathyroidism. It may also be part of routine monitoring for patients on certain medications or with chronic illnesses.

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 or supplements you’re taking to your appointment.

What Happens During the Test?

A healthcare professional will draw blood from a vein, typically in your arm. The process is quick and usually painless. The blood sample is sent to a lab for analysis.

What Do Results Mean?

Results alone don’t provide a diagnosis—they’re used alongside other tests and symptoms. Very high or very low phosphorus levels may signal underlying health concerns, but your doctor will interpret results in the context of your overall health.

Reference range

Adult: 2.5-4.5 mg/dLN/A

Specimen: stool

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 Phosphorus

Frequently asked questions

What Are Common Causes of Abnormal Results?
High phosphorus levels (hyperphosphatemia) can occur due to kidney disease, certain medications (like phosphate supplements or laxatives), or dehydration. Low phosphorus levels (hypophosphatemia) may result from malnutrition, excessive vitamin D, or conditions like diabetes or alcoholism.
How Often Should I Get This Test?
Your doctor will determine how often you need this test based on your health status, symptoms, and treatment plan. Regular monitoring may be recommended if you have chronic kidney disease, are on dialysis, or take medications that affect phosphorus levels.
Can I Take Anything to Lower or Raise Phosphorus Levels?
Yes, lifestyle changes can help. To lower phosphorus: reduce intake of dairy, nuts, and processed foods; drink water; and follow a doctor’s advice on phosphate-binding medications if prescribed. To raise phosphorus: eat foods like nuts, seeds, and legumes, but consult your doctor before making dietary changes.
  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