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24-Hour Urine Porphobilinogen-to-Creatinine Ratio

Published: August 9, 2026Updated: August 16, 2026

Measures porphobilinogen relative to creatinine in urine collected over 24 hours, helping evaluate suspected acute hepatic porphyria.

Quick summary

["An elevated result may suggest increased porphyrin precursor production, including during an acute porphyria attack."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
74910-1
Short code
Porph Fract+Creat Pnl 24h Ur-sRto
Synonyms
Porph Fract+Creat Pnl 24h Ur-sRto
Category
kidney
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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

What is this test?

This test measures porphobilinogen, a heme-production intermediate, in a 24-hour urine collection. The result is compared with the urine creatinine level to account for differences in urine concentration.

Why might I need this test?

It may be ordered when abdominal pain, neuropathy, mood changes, darkening urine, or other symptoms raise concern for an acute hepatic porphyria. It can also be used to monitor people with a confirmed porphyria.

How is the test performed?

Urine is collected into a special container for a full 24-hour period, usually beginning in the morning. The laboratory measures porphobilinogen and creatinine and calculates their ratio.

How do I prepare for the test?

Follow the collection instructions provided by the laboratory, including the start and end times and any storage requirements. Tell your clinician about medicines, alcohol, smoking, or major dietary changes, because these can affect the result.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

A markedly elevated porphobilinogen-to-creatinine ratio may indicate an acute hepatic porphyria, particularly during an attack. The result should be interpreted with symptoms, medical history, and other laboratory tests because urine porphobilinogen can occasionally be increased for other reasons.

Short name

24-Hour Urine Porphobilinogen/Creatinine Ratio

Frequently asked questions

Is this the same as a routine 24-hour urine test?
It uses a 24-hour urine collection but measures porphobilinogen relative to creatinine rather than general urine protein, electrolytes, or other routine substances.
Why is creatinine included in the result?
Creatinine helps show how concentrated the urine is. Including it makes the porphobilinogen measurement less dependent on variations in urine volume.
Do I need to stop taking medicines before collecting urine?
Do not stop prescribed medicines on your own. Ask your clinician whether any medication or lifestyle changes are needed, because abrupt changes could affect safety or test interpretation.
  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 16, 2026. · Read our editorial policy