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Phosphorus (Phosphate) Level in Serum or Plasma

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

This test measures the amount of phosphorus, an essential mineral, in your blood. Phosphorus helps maintain healthy bones, teeth, and cells.

Quick summary

["Phosphorus levels can affect bone health, kidney function, and metabolism—keep an eye on them if you have conditions like kidney disease or metabolic disorders."]

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

Key facts at a glance

LOINC
50898-6
Short code
Phosphate Hair-sCnt
Synonyms
Phosphate Hair-sCnt
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 It’s Done

Doctors may order this test to check for conditions like hypophosphatemia (low phosphorus) or hyperphosphatemia (high phosphorus), which can cause weakness, muscle cramps, or bone problems. It’s also used in monitoring treatments for kidney disease, cancer, or metabolic disorders.

What to Expect

A blood sample is taken from a vein, usually in your arm. You may feel a slight pinch, but it’s quick and painless. No special preparation is needed unless your doctor instructs otherwise.

Common Conditions Affecting Results

Low phosphorus levels can occur due to poor diet, kidney problems, or certain medications. High levels may result from overuse of phosphate supplements, kidney failure, or certain cancers.

Factors That Could Affect Results

Eating or drinking certain foods (like dairy or phosphorus supplements) within 24 hours of the test can influence results. Stress, illness, or certain medications may also play a role.

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.

Clinical Significance

Short name

Serum/Plasma Phosphate

Frequently asked questions

How often should I get this test?
Your doctor will determine how often you need this test based on your health status, symptoms, and any ongoing conditions. Regular monitoring may be needed if you have chronic kidney disease, metabolic bone disease, or are receiving treatments that affect phosphorus levels.
What do my results mean?
Results are typically compared to your baseline or reference ranges provided by your lab. If your levels are outside the normal range, your doctor will discuss potential causes and next steps with you.
Can I adjust my diet to manage phosphorus levels?
If your doctor suggests dietary changes, they’ll provide specific guidance. Generally, limiting high-phosphorus foods (like processed meats, carbonated drinks, and certain cheeses) may help if you have kidney issues, but always follow their advice.
  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