Phosphorus (Serum)
This test measures the amount of phosphorus, a mineral essential for healthy bones and cells, in your blood serum.
["Phosphorus levels help assess bone health and metabolic function."]
Key facts at a glance
- LOINC
- 59161-0
- Short code
- Phosphate Stl-sCnc
- Synonyms
- Phosphate Stl-sCnc
- 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 Is This Test Done?
Your doctor may order this test to check for conditions affecting bone metabolism, kidney function, or hormonal imbalances. It can also help monitor treatment responses for diseases like hyperparathyroidism or kidney 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 confirm with your lab. Bring any medications you’re taking.
What Happens During the Test?
A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but it’s quick and painless. The sample is sent to the lab for analysis.
What the Results Mean
Results are compared to a general reference range, but your actual values will be provided to your doctor for interpretation. Abnormally high or low levels may signal underlying health concerns.
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.
◆Associated findings1
Short name
Serum Phosphorus
Frequently asked questions
High phosphorus levels (hyperphosphatemia) can occur with kidney disease, certain cancers, or overuse of supplements, potentially weakening bones and causing itching. Low phosphorus levels (hypophosphatemia) may result from malnutrition, chronic kidney disease, or excessive vitamin D intake, leading to muscle weakness or bone pain.
Abnormal phosphorus levels can stem from kidney problems (e.g., failing kidneys retain phosphorus), hormonal imbalances (e.g., hyperparathyroidism), or conditions like diabetes, malnutrition, or excessive vitamin D exposure. Rarely, medications (e.g., certain diuretics or antacids) may also affect levels.
Your doctor will determine how often you need this test based on your health status. For example, people with kidney disease may need regular monitoring, while others may only need it once or twice a year.
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