5mthfhcysmtserccnc
This test measures the activity of methionine synthase enzyme in your blood, which is important for processing homocysteine and maintaining healthy cells.
{"Methionine synthase helps convert homocysteine to methionine using vitamin B12","Low enzyme activity may indicate vitamin B12 deficiency or genetic conditions","The test requires a simple blood sample","Results help diagnose certain types of anemia and neurological disorders"}
Key facts at a glance
- LOINC
- 1696-4
- Short code
- MTR; MS; MTRase
- Synonyms
- 5MTHF-Hcys-MT Ser-cCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or plain red top tube
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Enzymatic spectrophotometric assay measuring 5-methyltetrahydrofolate-dependent homocysteine remethylation to methionine
- CPT
- 82657 (Enzyme assay, 5-methyltetrahydrofolate-homocysteine methyltransferase)
- SNOMED
- 414561006 (Enzyme measurement)
- Specimen volume
- 1.0 mL serum minimum; 2.0 mL preferred for optimal testing
- Stability
- Serum should be separated from cells within 2 hours of collection. Store at 2-8°C if analysis within 7 days. For longer storage, freeze at -20°C or below. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 50
- Lipemia max
- 100
- Icterus max
- 20
- TAT
- 48–168 hours
- Order
- routine
What is this test?
The methionine synthase (MS) test measures the activity level of an enzyme in your blood called 5-methyltetrahydrofolate homocysteine methyltransferase. This enzyme plays a crucial role in converting homocysteine (an amino acid) into methionine (another amino acid) through a process that requires vitamin B12 (cobalamin) as a cofactor. Proper function of this enzyme is essential for DNA synthesis, cell division, and maintaining healthy nerve cells.
Why is this test performed?
Your healthcare provider may order this test if you have symptoms of vitamin B12 deficiency, such as fatigue, weakness, numbness or tingling in hands and feet, memory problems, or difficulty walking. It may also be used to investigate the cause of certain types of anemia (particularly megaloblastic anemia) or to evaluate patients with suspected inherited disorders affecting one-carbon metabolism.
How is the test performed?
A healthcare professional will draw a small sample of blood from a vein in your arm. The sample is then sent to a laboratory where specialists measure the activity of the methionine synthase enzyme. You do not need to fast before this test, but you should inform your doctor about any medications or supplements you are taking.
Understanding your results
Results are reported as enzymatic activity levels. Low methionine synthase activity typically suggests vitamin B12 deficiency or impaired B12 metabolism. In rare cases, genetic mutations can cause reduced enzyme function. Your doctor will interpret your results in combination with other tests, including serum B12 levels, homocysteine levels, and methylmalonic acid levels, to make an accurate diagnosis.
Reference range
Reference range varies by laboratory methodology; typically reported as enzyme activity units per liter (U/L). Contact local laboratory for institution-specific reference intervals.N/A
No special preparation required. Fasting is not necessary for this test. Inform physician of any vitamin B12 or folate supplementation as this may affect enzyme activity results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings2
Frequently asked questions
Do I need to fast before this test?
What do low methionine synthase levels mean?
Can supplements affect my results?
How long does it take to get results?
Is this test painful?
Sources
- 1
- 2
- 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 10, 2026. · Read our editorial policy