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Phosphorus (Serum) Concentration

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

This test measures the amount of phosphorus, a mineral essential for healthy bones, cells, and energy production, in your blood serum.

Quick summary

["Assesses phosphorus levels that may affect bone health or metabolic balance."]

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

Key facts at a glance

LOINC
110637-6
Short code
Phosphate Msmt Stl
Synonyms
Phosphate Msmt Stl
Category
electrolyte
Sample
stool
Container
Clean container
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 g
Stability
Refrigerated: 24h, Frozen: 7d
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, fatigue, bone pain, or if you’re being treated for conditions like kidney disease, hyperparathyroidism, or malnutrition. It may also be part of routine monitoring for patients on certain medications or with metabolic disorders.

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 any medications or supplements you’re taking to discuss with your provider.

How the Test Is Performed

A blood sample is taken from a vein in your arm by a healthcare professional. The serum portion is separated and analyzed for phosphorus concentration using an automated chemical method.

What the Results Mean

Results are compared to standard reference ranges, though exact values can vary by lab. Low phosphorus (hypophosphatemia) may indicate kidney issues or excessive loss, while high levels (hyperphosphatemia) could signal kidney dysfunction or overuse of phosphate-containing supplements.

Reference range

Adult: 2.5-4.5 mg/dLN/A

Specimen: stool

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.

Abnormal phosphorus levels can impact bone mineralization, muscle function, and energy metabolism. Chronic imbalances may lead to complications like bone fractures, muscle cramps, or even heart problems. Your provider will interpret results in the context of your overall health and symptoms.

Short name

Serum Phosphorus

Frequently asked questions

How long does it take to get my test results?
Results are typically available within 1–3 business days, depending on your lab’s processing schedule. Follow up with your provider if you have questions about your specific results.
Can I eat or drink before this test?
If fasting is required, avoid food and liquids (except water) for 8–12 hours before your blood draw. If no fasting is needed, you can eat and drink normally. Always check with your provider for exact instructions.
What causes low or high phosphorus levels?
Low phosphorus can result from kidney disease, excessive vitamin D, or malabsorption issues. High phosphorus may stem from kidney failure, certain medications, or overconsumption of phosphate supplements. Lifestyle factors like diet (e.g., dairy, nuts) can also influence levels.
  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