Skip to content

Phosphorus (Serum/Plasma Concentration)

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 normal cell function.

Quick summary

["Phosphorus levels can indicate bone health and metabolic balance."]

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

Key facts at a glance

LOINC
35221-1
Short code
Phosphate SerPl-msCnc
Synonyms
Phosphate SerPl-msCnc
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 healthcare provider may recommend this test if you have symptoms like muscle weakness, bone pain, or kidney issues. It’s also used to monitor conditions like kidney disease, metabolic disorders, or after treatments affecting phosphorus levels.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re on a phosphate-restricted diet, check with your doctor first.

What the Results Mean

Results help assess whether phosphorus levels are too high or too low, which can affect how your body uses energy, builds bones, and functions overall.

Common Conditions Affecting Phosphorus Levels

High phosphorus levels (hyperphosphatemia) can occur with kidney disease or certain medications. Low levels (hypophosphatemia) may be linked to malnutrition, diarrhea, or overuse of phosphate binders.

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.

Phosphorus levels play a critical role in bone mineralization, red blood cell function, and energy metabolism. Abnormalities can lead to weakened bones, muscle cramps, or even heart problems in severe cases.

Short name

Serum Phosphorus Level

Frequently asked questions

What causes abnormal phosphorus levels in my blood?
Abnormal levels can result from kidney problems (which filter waste, including phosphorus), certain medications, or conditions like diabetes or malnutrition. Kidney disease is the most common cause of high phosphorus.
How often should I get this test?
Your doctor will determine frequency based on your health needs—such as monitoring kidney function, managing a chronic condition, or checking for metabolic imbalances. Follow their guidance.
Can diet affect phosphorus test results?
Yes, high-phosphorus foods (like dairy, nuts, or processed foods) may temporarily raise levels. If you’re on a restricted diet, discuss it with your provider before testing.
  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