Phosphorus (Serum) Concentration
This test measures the amount of phosphorus, an essential mineral, in your blood serum. Phosphorus helps maintain healthy bones, teeth, and cells, and is involved in energy production.
["Your blood phosphorus levels can help doctors assess bone health, kidney function, and metabolic balance."]
Key facts at a glance
- LOINC
- 48641-5
- Short code
- Phosphate pre dial SerPl-mCnc
- Synonyms
- Phosphate pre dial SerPl-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 This Test Might Be Ordered
Your doctor may recommend this test if you have symptoms like muscle weakness, fatigue, bone pain, or if they suspect conditions such as kidney disease, metabolic disorders, or disorders affecting bone metabolism. It may also be used to monitor treatment for conditions like hyperparathyroidism or phosphate disorders.
What to Expect Before the Test
No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it’s part of a metabolic panel, but always follow your doctor’s instructions. Bring any medications you’re taking, as some may affect results.
How the Test Is Performed
A blood sample is drawn from a vein, usually in your arm. The blood is then sent to a lab where it is analyzed to measure phosphorus concentration. The test is typically done using a standard biochemical assay method.
Possible Results and Interpretation
Results are reported as a mass concentration in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). While reference ranges vary by lab, low or high levels may signal underlying health concerns that need further evaluation.
Reference range
Adult: 2.5-4.5 mg/dLN/A
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 lead to muscle weakness, bone pain, or even seizures, especially in severe cases. High phosphorus levels (hyperphosphatemia) may indicate kidney problems, metabolic disorders, or overuse of phosphate supplements. Both conditions can affect bone health and energy metabolism, so monitoring is important for patients with chronic illnesses like kidney disease or diabetes.
Short name
Serum Phosphate
Frequently asked questions
What does a normal phosphorus level mean for me?
How can I manage phosphorus levels if they’re out of range?
Can diet or medications affect this test result?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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