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Phosphorus (Serum or Plasma) 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 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
49006-0
Short code
Phosphate DiafP-sCnc
Synonyms
Phosphate DiafP-sCnc
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
SNOMED
394971007
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 Is Done

Your doctor may order this test to check for conditions affecting bone density, kidney function, or metabolic disorders. It can also help monitor treatment progress for conditions like hyperparathyroidism, kidney disease, or metabolic bone diseases.

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 blood thinner, inform your healthcare provider before the test.

What the Results Mean

Results are compared to a general reference range, but exact values can vary by lab. Low levels may suggest kidney problems or vitamin D deficiency, while high levels could indicate overactive parathyroid glands or kidney issues.

Common Conditions Linked to Abnormal Results

Low phosphorus levels might be seen in malnutrition, kidney disease, or excessive calcium intake. High levels can occur with kidney failure, overuse of antacids, or certain medications.

Reference range

Adult: 2.5-4.5 mg/dLN/A

Specimen: serum

No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Phosphorus levels are critical for bone mineralization, energy production, and cell function. Abnormalities can signal underlying metabolic or organ-related disorders requiring medical evaluation.

Short name

Serum Phosphorus

Frequently asked questions

What causes low phosphorus levels in blood?
Low phosphorus levels can result from conditions like kidney disease, malnutrition, or excessive use of certain medications (e.g., antacids). Lifestyle factors, such as poor diet or vomiting/diarrhea, may also contribute.
How long does it take to get phosphorus test results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will discuss them with you during your follow-up visit.
Can diet affect phosphorus test results?
Yes, dietary intake of phosphorus (found in dairy, nuts, and processed foods) can influence results. Avoiding high-phosphorus foods for 24 hours before testing may help standardize results, but this isn’t always necessary.
  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