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24-Hour Urinary Phosphate Excretion Rate

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

This test measures how much phosphate (a mineral) your kidneys excrete over a 24-hour period in your urine. It helps assess kidney function and phosphate metabolism.

Quick summary

["This test helps evaluate kidney health and phosphate balance in your body."]

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

Key facts at a glance

LOINC
59167-7
Short code
Phosphate 24h Stl-sRate
Synonyms
Phosphate 24h Stl-sRate
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 Is Done

Your doctor may order this test if they suspect kidney problems, such as chronic kidney disease, or if you have conditions affecting phosphate levels, like hyperparathyroidism or certain metabolic disorders. It can also be used to monitor long-term kidney function or diagnose phosphate-related issues.

How the Test Works

You’ll collect all your urine over a full 24-hour period and provide a sample to the lab. The lab then analyzes the phosphate content in your urine to determine your excretion rate.

Sample Collection

To collect your urine properly, start by emptying your bladder at the beginning of the test (this urine is discarded). Then, collect every bit of urine you pass for the next 24 hours, including during the night. Store the urine in a cool, sealed container and bring the full sample to your doctor or lab on the following day.

What to Expect

There are no special preparations needed, but you may need to wear a special urine collection bag or container if you’re at home. Avoid certain medications or foods that could interfere with the test results, as advised by your doctor.

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.

Clinical Significance

Short name

Phosphate Urine Rate

Frequently asked questions

How Often Should I Get This Test?
Your doctor will determine how often you need this test based on your health condition, symptoms, and other tests. It’s usually done as part of a routine evaluation or if you have known kidney or metabolic issues.
Can I Eat or Drink Anything Before the Test?
No specific diet or fluids are restricted before the test, but avoid medications that might affect phosphate levels unless your doctor advises otherwise. Follow your doctor’s instructions for any special preparations.
What If I Missed Collecting My Urine Sample?
If you miss any urine during the 24-hour period, you’ll need to restart the collection. If you’re unsure, contact your doctor or lab immediately to avoid inaccurate results.
  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