Free Hydroxylysine/Creatinine Ratio, 24-Hour Urine
A 24-hour urine test that measures free hydroxylysine relative to creatinine, providing information about collagen breakdown and bone turnover.
["Elevated urinary hydroxylysine may indicate increased collagen breakdown or bone turnover."]
Key facts at a glance
- LOINC
- 49849-3
- Short code
- OH-Lysine Free/Creat 24h Ur-sRto
- Synonyms
- OH-Lysine Free/Creat 24h Ur-sRto
- Category
- kidney
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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
What is this test?
This test measures free hydroxylysine, a substance released when collagen is broken down, in urine collected over 24 hours. The result may also be compared with urine creatinine to help account for differences in urine concentration.
Why might I need this test?
A clinician may order this test as part of a specialist evaluation of bone turnover, collagen metabolism, or suspected metabolic bone disease. It is not usually a routine screening test.
How is the test performed?
You collect all urine for a full 24-hour period, usually beginning after emptying your bladder in the morning. The laboratory then measures free hydroxylysine and creatinine and may report the hydroxylysine-to-creatinine ratio.
How do I prepare for the test?
Follow the collection instructions provided by the laboratory, including the exact start and stop times. Keep the container refrigerated if instructed, record any missed collections, and ask your clinician whether unusual exercise or collagen-rich foods should be avoided.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Higher urinary free hydroxylysine can reflect increased collagen breakdown or bone resorption. This may be seen in conditions involving increased bone turnover, such as Paget disease, hyperparathyroidism, osteomalacia, or bone metastases. Results must be interpreted with symptoms, imaging, and other bone tests because collection errors and factors affecting collagen or creatinine can also influence the result.
Short name
24-Hour Urine Hydroxylysine
Frequently asked questions
Is this the same as a routine kidney function test?
Why is a 24-hour urine collection required?
What if part of the urine collection is missed?
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 16, 2026. · Read our editorial policy