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Phosphorus (Phosphate) in Serum or Plasma

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 levels help assess bone health and metabolic function."]

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

Key facts at a glance

LOINC
38717-5
Short code
Phosphate Air-mCnc
Synonyms
Phosphate Air-mCnc
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 Is This Test Done?

Your doctor may order this test to check for conditions affecting phosphorus balance, such as kidney disease, vitamin D deficiency, or metabolic disorders. It can also help monitor treatment responses for conditions like hyperparathyroidism or certain cancers.

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 test if it involves a blood draw. If you’re on certain medications (like phosphate binders), your doctor will advise you.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. The sample is then sent to a lab for analysis using a blood chemistry test.

What Are Normal Results?

Results vary by lab and method, but your doctor will compare your results to your specific reference range. Abnormal levels may signal underlying health concerns.

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.

Low phosphorus levels (hypophosphatemia) can cause weakness, muscle cramps, or bone pain, while high levels (hyperphosphatemia) may lead to kidney issues, heart problems, or calcium deposits in tissues. Chronic imbalances can affect metabolism, nerve function, and bone health.

Short name

Phosphorus Level

Frequently asked questions

What causes low phosphorus levels?
Conditions like malnutrition, kidney disease, excessive sweating, or certain medications (e.g., antacids, diuretics) can lower phosphorus. Severe cases may also result from overactive thyroid or liver disease.
What causes high phosphorus levels?
Kidney failure, certain cancers, or overuse of phosphate supplements can raise phosphorus. Excessive vitamin D or rapid cell breakdown (e.g., from chemotherapy) may also contribute.
How is phosphorus treated?
Treatment depends on the cause. For low levels, dietary adjustments (e.g., avoiding phosphate-rich foods) or supplements may be recommended. For high levels, medications like calcium-based binders or dialysis may be needed.
  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