MTHFR Gene Test

What is an MTHFR Gene Test?

An MTHFR Gene Test is a genetic test that looks for common variants of the MTHFR (methylenetetrahydrofolate reductase) gene. This gene provides instructions for making an enzyme involved in processing folate, also known as vitamin B9.

Folate, vitamin B12 and vitamin B6 help the body to break down an amino acid called homocysteine. If this process does not work correctly, homocysteine may build up in the blood, causing damage to the inner lining of artery walls, blood vessel blockages, and an increased risk of dangerous blood clots. However, MTHFR variants are only one possible influence on homocysteine levels.

The two commonly tested MTHFR variants in this test are:

• C677T 
• A1298C

These variants are common in the population and have an impact on MTHFR enzyme activity. Finding one variant does not mean that a person has a disease, a folate deficiency or a high homocysteine level. Many people have one or two copies of a common MTHFR variant and remain healthy.

For this reason, healthcare providers interpret the result alongside the person’s medical history and other laboratory findings. These may include homocysteine, folate and vitamin B12 levels.

Repeated or routine tests may not be needed for everyone. Many healthcare professionals recommend performing it only once, as inherited DNA remains the same.

What Can This Test Tell You?

The test can show whether a person has one or two copies of the MTHFR variants included in the laboratory analysis. It may help a healthcare provider understand a persistently high homocysteine result in a specific clinical situation.

However, the test cannot show:

• Whether a person currently has a folate deficiency 
• Whether homocysteine is high without measuring it separately 
• Whether a person will develop a blood clot or heart disease 
• Whether a pregnancy complication will occur 
• Whether the person needs a specific supplement or treatment 
• Whether every possible change in the MTHFR gene is present 

The scope of the test matters. A result for C677T and A1298C does not represent a complete analysis of every possible MTHFR variant.

Major medical genetics guidance advises against using common MTHFR variant testing as a routine test for inherited thrombophilia or recurrent pregnancy loss. 

What are the Symptoms that Prompt this Test?

An MTHFR Gene Test is not usually ordered because of symptoms alone. Common MTHFR variants often do not cause any noticeable symptoms.

A healthcare provider may consider the test when evaluating:

• Persistently elevated homocysteine 
• A close relative with a documented MTHFR variant 
• A suspected inherited metabolic condition 
• Findings that suggest rare, severe MTHFR deficiency 
• A specific clinical or pharmacogenetic question 

High homocysteine can have many causes other than an MTHFR variant. These include low vitamin B12 or folate, kidney disease, hypothyroidism, certain medicines, smoking and increasing age. That’s why a homocysteine result needs a wider assessment.

Conditions That May Require This Test

An MTHFR Gene Test may be considered when evaluating:

• MTHFR gene variants
• Severe MTHFR deficiency
• Elevated homocysteine (hyperhomocysteinemia)
• Certain rare inherited metabolic disorders

Healthcare providers generally do not use common MTHFR variant testing alone to diagnose blood clots, recurrent pregnancy loss, or other common health conditions.

How is the Test Performed?

Preparation

• Fasting is usually not required. 
• Tell your doctor about your medical and family history. 
• Mention if there are any previous high homocysteine results. 
• Share details of the vitamins and supplements you take, particularly folic acid, folate, vitamin B6 and vitamin B12. 
• Follow any additional instructions provided by the laboratory. 

Supplements do not change a person’s genetic result. However, they may influence folate, vitamin B12 or homocysteine levels if these are tested at the same time.

Sample Collection

A healthcare professional collects blood sample for MTHFR gene test. The process involves: 

• Disinfecting the area from where the needle has to be inserted for sample collection
• Collecting a small amount of blood by inserting sterile needle into the vein
• Careful sample storage in the sample tube
• Transporting the sample to the genetics laboratory

The blood draw usually takes a few minutes. Mild discomfort or bruising may occur at the collection site.

Lab Analysis

DNA is extracted from the blood sample. The laboratory then analyses the specific parts of the MTHFR gene included in the test, usually through a molecular method such as PCR-based genotyping.

Results of MTHFR Gene Test

The MTHFR gene test doesn’t have a numerical reference range. It is a genetic test that indicates whether specific variants included in the test were detected.

Lab results may show that a person has: 

• No tested variant – The MTHFR variants included in the test were not identified. 
• Heterozygous Variant: One copy of a specific variant was identified.
• Homozygous Variant: Two copies of the same variant were identified.
• Compound Heterozygous: Two different variants, such as C677T and A1298C, were identified.

“Results may be interpreted differently depending on the laboratory. Consult your healthcare provider to interpret results correctly.”

Understanding Your Results

An abnormal MTHFR Gene Test result means that one or more genetic variants were identified. The significance of the result depends on the specific variant tested and whether it affects MTHFR enzyme function.

MTHFR Variant Detected

Common variants such as C677T and A1298C may affect enzyme activity to varying degrees. Whether there is one copy of a particular variant, two copies of the same variant, or a copy of two different variants, it does not mean a treatment is required.

Many people with these variants have no health problems and have normal homocysteine or folate levels.

Your healthcare provider will assess your overall symptoms and health history and may consider checking:

• Homocysteine level
• Folate level
• Vitamin B12 level
• Vitamin B6 level
• Complete Blood Count (CBC)
• Kidney function
• Thyroid function

Negative Test Result

A negative result means that the particular variants included in the test were not found. It does not exclude:

• Other rare MTHFR variants 
• Vitamin deficiency 
• Kidney or thyroid disease
• Other causes for high homocysteine 
• Inherited metabolic disorder

If the symptoms or laboratory findings of the patient don’t give a meaningful picture, further investigation may be required.

Does an MTHFR Variant Confirm a Clotting Disorder?

No. Common MTHFR variants are not considered inherited thrombophilias. A positive result cannot confirm why a person developed a blood clot and should not replace an appropriate clotting evaluation.

If there is a personal or family history of thrombosis, the healthcare provider may consider other investigations based on the clinical circumstances.

Does a Positive Result Mean Folic Acid Must Be Avoided?

No. People with common MTHFR variants can process folate, including folic acid. A common variant is not, by itself, a reason to avoid folic acid.

People who may become pregnant are still advised to follow established folic acid recommendations because folic acid helps prevent neural tube defects. Decisions about the type or amount of any supplement should be discussed with a qualified healthcare provider.

Severe MTHFR Deficiency

Common variants such as C677T and A1298C should not be confused with rare pathogenic MTHFR variants that can cause severe enzyme deficiency. Rare pathogenic variants reduce MTHFR enzyme activity, can cause severe elevations in homocysteine and may be associated with neurological or developmental problems.

Possible symptoms in severe cases may include:

• Developmental delay
• Intellectual disability
• Seizures
• Muscle weakness
• Movement problems
• Blood clotting complications

These rare conditions require specialised medical evaluation and management.

An experienced healthcare professional interprets results based on a patient’s symptoms and medical history. Additional testing and treatment plans are recommended accordingly.

Schedule Your Appointment

Looking for an MTHFR Gene Test? Book your appointment now for accurate genetic testing and expert laboratory support that you can trust.