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Phosphorus (Serum/Plasma Mass 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.

Quick summary

["Phosphorus helps maintain bone strength and supports energy production in your body."]

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

Key facts at a glance

LOINC
14408-9
Short code
Phosphate Amn-mCnc
Synonyms
Phosphate Amn-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 doctor may request this test if you have symptoms like muscle weakness, bone pain, or unusual fatigue. It could also be checked if you have conditions affecting kidney function, diabetes, or metabolic disorders. Sometimes, it’s part of routine monitoring for patients on certain medications or with chronic illnesses like cancer or heart disease.

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 draw if your test is part of a metabolic panel. Bring a list of medications you’re taking, as some can affect results.

How the Test Works

A small blood sample is taken from a vein in your arm. The sample is sent to a lab where phosphorus levels are measured using a specialized analytical method to detect its concentration in your blood.

What the Results Mean

Results are compared to a reference range specific to your age, sex, and overall health. Low or high levels may signal underlying health issues, but interpretation depends on your full medical picture.

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 weakness, muscle cramps, or even seizures in severe cases. High phosphorus levels (hyperphosphatemia) may indicate kidney problems, metabolic disorders, or overuse of phosphate-containing supplements. Both extremes can disrupt normal bodily functions, including bone health and energy metabolism.

Short name

Phosphorus Level

Frequently asked questions

What causes low phosphorus levels?
Low phosphorus can result from poor diet (low intake of foods like dairy, nuts, or legumes), kidney disease (which fails to reabsorb phosphorus), excessive sweating, or certain medications (e.g., antacids, diuretics). Rarely, it can be caused by overactive thyroid or liver disease.
What causes high phosphorus levels?
High phosphorus is often linked to kidney problems (where the body can’t excrete it properly), certain cancers (like multiple myeloma), or overuse of phosphate supplements. It can also occur in patients on dialysis or those with untreated diabetes.
Can lifestyle changes affect phosphorus levels?
Yes! Dietary adjustments (e.g., limiting phosphate-rich foods) and managing conditions like kidney disease can help balance phosphorus levels. Always follow your doctor’s advice tailored to your specific needs.
  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