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N-Acetyl-L-Methionine/Creatinine Ratio, Urine

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

A urine test that measures N-acetyl-L-methionine relative to creatinine to help evaluate certain inherited metabolic disorders.

Quick summary

["This specialized urine test can help identify and monitor metabolic conditions affecting methionine or vitamin B12 metabolism."]

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

Key facts at a glance

LOINC
104699-4
Short code
N-acetyl-L-methionine/Creat Ur-sRto
Synonyms
N-acetyl-L-methionine/Creat 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 N-acetyl-L-methionine, a compound related to methionine metabolism, in urine. The result is compared with the urine creatinine level, which helps account for differences in urine concentration.

Why might I need this test?

This test may be ordered by a genetics or metabolic specialist when an inherited disorder affecting methionine, vitamin B12, or related metabolic pathways is suspected. It may also be used to monitor an established metabolic condition.

How is the test performed?

A urine specimen is collected and analyzed in the laboratory for N-acetyl-L-methionine and creatinine. The laboratory then reports the amount of N-acetyl-L-methionine relative to the amount of creatinine.

How do I prepare for the test?

Follow the urine collection instructions provided by your healthcare professional, including any timing, container, and storage requirements. Tell the laboratory if you are taking vitamin B12 or other supplements, because supplementation may affect the interpretation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

An elevated ratio may occur in methylmalonic acidemia, homocystinuria, vitamin B12 metabolism disorders, or related inherited metabolic conditions. Results must be interpreted with symptoms, genetic testing, blood tests, and other urine studies because an abnormal result does not identify one specific disorder by itself.

Short name

Urine N-acetyl-L-methionine

Frequently asked questions

Is this a routine urine test?
No. It is a specialized metabolic test usually ordered when a clinician suspects or is monitoring an inherited condition involving methionine or vitamin B12 metabolism.
Why is the result divided by creatinine?
Urine concentration can vary from sample to sample. Creatinine is used as a reference measurement so the N-acetyl-L-methionine result better reflects the amount excreted rather than the concentration of the urine itself.
Can vitamin B12 supplements affect the result?
They may. Inform the healthcare professional and laboratory about vitamin B12, folate, methionine, and other relevant supplements before or at the time of testing.
  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