Phosphorus (Phosphate) 24-Hour Urinary Excretion Rate
This test measures how much phosphorus (a mineral important for bones and cells) is excreted in your urine over a 24-hour period. It helps assess kidney function and phosphate balance in your body.
["This test helps doctors check if your kidneys are removing enough phosphorus from your body."]
Key facts at a glance
- LOINC
- 35263-3
- Short code
- Phosphate 24h Ur-msRate
- Synonyms
- Phosphate 24h Ur-msRate
- Category
- electrolyte
- Sample
- urine
- Container
- Sterile urine 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
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your doctor may order this test if they suspect kidney problems, such as chronic kidney disease, or if you have conditions like hyperphosphatemia (too much phosphorus in your blood) or hypophosphatemia (too little). It can also be used to monitor phosphate levels in people with certain metabolic disorders or those on phosphate-binding medications.
How the Test Works
You’ll collect all your urine for a full 24-hour period, typically starting and ending at the same time each day. The urine is then sent to a lab for analysis to determine the total phosphorus content.
Sample Collection
To collect urine for this test, you’ll need to: • Start collecting urine immediately after waking up. • Empty your bladder completely into a clean container. • Collect all urine for the next 24 hours, including any overnight urine. • Keep the container refrigerated if possible. • Finish collecting urine at the same time the next day and send it all to the lab together.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to avoid certain medications or supplements that could affect results. Your doctor might also advise you to drink enough water to help flush out phosphorus naturally.
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.
High urinary phosphate excretion may indicate kidney dysfunction, excessive intake of phosphate-rich foods, or certain metabolic conditions. Low excretion could suggest kidney disease, malabsorption issues, or other disorders affecting phosphate metabolism. This test helps guide treatment decisions, such as dietary adjustments or medication management.
Short name
24-Hour Urine Phosphate
Frequently asked questions
What causes abnormal phosphate levels in urine?
Does diet affect this test?
How long does it take to get results?
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