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Understanding Your Laboratory Test: What It Is, How the Sample Is Collected, and Why It Is Performed

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

This test checks for the presence of 5-Methyltetrahydrofolate, the active form of folate, in the cerebrospinal fluid surrounding the brain and spinal cord.

Quick summary

{"Measures active folate levels in the fluid around the brain and spinal cord","Helps diagnose folate-related neurological conditions","Requires a lumbar puncture (spinal tap) to collect the sample","Low levels may indicate cerebral folate deficiency","Important for evaluating certain brain development and neurological disorders"}

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

Key facts at a glance

LOINC
33274-2
Short code
5MTHF CSF
Synonyms
5Me-tetrahydrofolate CSF Ql
Category
chemistry
Sample
csf
Container
Sterile polypropylene cryovial or sterile CSF collection tube (no preservatives)
Units
N/A
Ref low
2.7
Ref high
17
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) or High-performance liquid chromatography (HPLC) with electrochemical detection
CPT
83789
SNOMED
104171000
Specimen volume
1-2 mL of CSF
Stability
Store at -70°C or below. Stable for up to 30 days at -70°C. Avoid repeated freeze-thaw cycles. Transport on dry ice.
Hemolysis max
200
TAT
72–168 hours
Order
routine

What is this test, and what can it tell my healthcare provider about my health?

The 5-Methyltetrahydrofolate (5-MTHF) test measures the amount of this active form of folate in your cerebrospinal fluid (CSF). CSF is the clear, protective fluid that surrounds your brain and spinal cord. Folate (vitamin B9) is essential for many bodily functions, and 5-MTHF is the form of folate that can cross the blood-brain barrier to support brain function.

How is the sample for this test collected, and what should I expect during the collection process?

The sample is collected through a procedure called a lumbar puncture, also known as a spinal tap. A healthcare provider inserts a thin needle between the bones in your lower spine to withdraw a small amount of cerebrospinal fluid. The procedure is generally safe and takes only a few minutes.

Why might my doctor order this test, and what health conditions can it help detect or monitor?

This test is typically ordered to evaluate neurological symptoms that may be related to folate deficiency in the brain, such as developmental delays, cognitive issues, movement disorders, or seizures. It helps doctors determine if there is a cerebral folate deficiency, which may not be detected by standard blood folate tests.

Reference range

NCBI: Folate 2.7-17.0 ng/mLN/A

Specimen: csf

No specific patient preparation required. Inform patient about the lumbar puncture procedure and obtain informed consent. Assist patient into lateral decubitus position with knees drawn to chest.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormal 5-MTHF levels in CSF may indicate cerebral folate deficiency syndrome, a condition where the brain does not receive enough folate despite normal blood levels. This can lead to neurological symptoms including developmental regression, movement disorders, speech delays, and seizures. The test is also useful in evaluating certain inherited disorders of folate metabolism and monitoring treatment response in patients with neurological conditions related to folate deficiency.

Frequently asked questions

Do I need to fast before this test?
Typically, no fasting is required for this test. However, follow any specific instructions provided by your healthcare provider.
Is the lumbar puncture painful?
A local anesthetic is used to numb the area, so you may feel some pressure but minimal pain during the procedure. You may experience a headache afterward, which can be managed with rest and fluids.
How long does it take to get results?
Results may take several days to a week, as this is a specialized test that may be sent to a reference laboratory.
What do low levels mean?
Low levels of 5-MTHF in CSF may indicate cerebral folate deficiency, which can affect brain development and function. Your healthcare provider will recommend appropriate treatment, which often includes folate supplementation.
  1. 1
    MedlinePlus - Lumbar PunctureSource
  2. 2
    National Institutes of Health - FolateSource

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