What Can Your Genes Tell You About How Your Body Processes Folate?

Folate often enters the conversation during pregnancy, usually when prenatal vitamins come up. But vitamin B9 has jobs throughout the body. It contributes to DNA synthesis and cell division and plays an important role in amino acid metabolism (National Institutes of Health, Office of Dietary Supplements [NIH ODS], n.d.).

Genetics can influence parts of this process. One gene in particular, MTHFR, has received plenty of attention online, sometimes accompanied by claims that go much further than the evidence.

Common MTHFR variants can affect folate metabolism, but having one doesn’t automatically mean you are folate deficient, can’t process folic acid, or need a particular type of supplement (Centers for Disease Control and Prevention [CDC], 2026). Understanding what your genes can actually tell you makes it easier to separate useful information from unnecessary worry.

What Is Folate, Exactly?

Folate is the general term for forms of vitamin B9. It occurs naturally in foods including leafy greens, asparagus, beans, peas, avocado, and citrus fruits. Folic acid is a form used in dietary supplements and fortified foods, while 5-methyltetrahydrofolate, usually shortened to 5-MTHF, is the main form of folate circulating in plasma (NIH ODS, n.d.).

For U.S. readers, the National Institutes of Health lists the recommended dietary allowance for most adults as 400 micrograms of dietary folate equivalents, or DFE, per day. During pregnancy, this rises to 600 micrograms DFE (NIH ODS, n.d.).

Separately, U.S. CDC guidance recommends that people who could become pregnant consume 400 micrograms of folic acid daily to help prevent neural tube defects (CDC, 2026). Recommendations can differ between countries, so readers outside the United States should follow guidance from their national health authority or healthcare professional.

Where the MTHFR Gene Fits In

MTHFR stands for methylenetetrahydrofolate reductase. The gene provides instructions for making an enzyme involved in one of the body’s folate-dependent pathways (National Library of Medicine, n.d.).

Chemically, the MTHFR enzyme catalyzes the conversion of 5,10-methylenetetrahydrofolate into 5-methyltetrahydrofolate, or 5-MTHF. The 5-MTHF can then provide a methyl group for a separate, vitamin B12-dependent reaction in which methionine synthase converts homocysteine to methionine (National Library of Medicine, n.d.; NIH ODS, n.d.).

That distinction matters. MTHFR helps produce the folate form required for the pathway, but the MTHFR enzyme itself doesn’t directly convert homocysteine into methionine.

Some people encounter the subject after taking a genetic test. An MTHFR gene test from Fenix Health uses an at-home cheek swab and reports MTHFR genotype information, including the common C677T and A1298C variants, along with estimated MTHFR activity (Fenix Health Science, n.d.).

Genetic information like this can tell you which tested variants you carry. It can’t tell you your current folate level, and it isn’t a diagnosis. Fenix Health Science similarly states that its genetic reports are for informational purposes and should be interpreted in the context of personal and family medical history, with a healthcare professional or genetic counselor where appropriate.

Why C677T Gets Particular Attention

Everyone inherits two copies of the MTHFR gene, one from each parent. For the C677T position, a person may therefore have the CC, CT, or TT genotype.

Of the common variants, C677T has clearer evidence of an effect on MTHFR function and blood folate concentrations. The T allele is associated with reduced folate-processing capacity, with the effect most apparent in people who inherit two T copies and therefore have the 677 TT genotype (Tsang et al., 2015).

A systematic review and meta-analysis by Tsang et al. (2015) examined trials and observational studies involving women ages 12 to 49. It found a consistent pattern in which folate concentrations were highest in CC participants, followed by CT and then TT participants when recommended microbiological testing methods were used.

The practical difference should still be kept in perspective. The CDC (2026) reports that, with the same amount of folic acid intake, people with the 677 TT genotype have blood folate concentrations about 16% lower on average than people with the 677 CC genotype. The agency also emphasizes that consuming 400 micrograms of folic acid can raise blood folate levels regardless of MTHFR genotype.

As the CDC (2026) explains, “Your folic acid intake is more important than your MTHFR genotype” when considering blood folate levels.

The evidence for A1298C shouldn’t simply be treated as equivalent to C677T. Current CDC guidance states that there isn’t enough evidence to show that A1298C on its own significantly affects how the body processes folate (CDC, 2026).

Your Genotype Isn’t the Same as Your Folate Status

A DNA test answers one kind of question: What genetic variants are present?

Blood tests answer different questions. Serum folate is influenced by recent intake, while red-blood-cell, or erythrocyte, folate provides a longer-term picture of folate status. Plasma homocysteine can provide information about the function of folate-dependent metabolism, but it isn’t specific to folate because factors such as vitamin B12 status and kidney function can also affect it (NIH ODS, n.d.).

That is why a genotype shouldn’t be used as a substitute for biochemical testing when a healthcare professional is investigating suspected folate deficiency or another medical concern.

The same caution applies to symptoms. An MTHFR variant alone can’t establish why someone feels fatigued, has fertility difficulties, experiences mood changes, or develops a pregnancy complication. Many genetic, nutritional, environmental, and medical factors can contribute to health outcomes.

Having an MTHFR Variant Doesn’t Mean You Can’t Use Folic Acid

Perhaps the most important misconception to clear up is the idea that people with common MTHFR variants can’t process folic acid.

The CDC (2026) states that people with MTHFR variants can process all forms of folate, including folic acid. It also notes that folic acid remains the only form of folate demonstrated to help prevent neural tube defects.

For U.S. readers who could become pregnant, the recommendation to consume 400 micrograms of folic acid daily, therefore, still applies even when an MTHFR variant is present (CDC, 2026).

This doesn’t mean every person should take the same supplement or dose. Medical history matters, and some people receive different recommendations from their clinicians. A genetic result is best viewed as one piece of information rather than a reason to change a prenatal vitamin or supplement without professional guidance.

Does Everyone Need MTHFR Testing?

No. Genetic testing can satisfy curiosity or provide specific genotype information, but common MTHFR testing isn’t a routine medical requirement for everyone.

This is particularly important when MTHFR is discussed in connection with blood clots. The American College of Medical Genetics and Genomics concluded that common MTHFR polymorphism testing has minimal clinical utility as part of a routine thrombophilia evaluation (Hickey et al., 2013). The recommendation was later reaffirmed and reclassified as a Clinical Practice Resource (Bashford et al., 2020).

That recommendation has a specific context: evaluating thrombophilia. It doesn’t mean genetic information is incapable of telling someone which MTHFR variants they carry. It means the presence of a common variant should not automatically be treated as evidence of a blood-clotting disorder.

Conclusion

Genes can give you useful clues about folate metabolism, but they can’t tell the whole story.

The MTHFR C677T variant, particularly the TT genotype, is associated with differences in folate-processing capacity and blood folate concentrations (Tsang et al., 2015). Yet diet, folic acid intake, health status, medications, and other biological factors also influence what happens in the body.

Current U.S. CDC guidance is clear that people with common MTHFR variants can process folic acid and that those who could become pregnant should obtain 400 micrograms daily (CDC, 2026).

Genes provide context. Good health decisions come from putting that context alongside nutrition, medical history, appropriate testing, and individual healthcare advice.

References

Bashford, M. T., Hickey, S. E., Curry, C. J., & Toriello, H. V. (2020). Addendum: ACMG practice guideline: Lack of evidence for MTHFR polymorphism testing. Genetics in Medicine, 22, 2125. https://doi.org/10.1038/s41436-020-0843-0

Centers for Disease Control and Prevention. (2026, July 16). MTHFR gene variant and folic acid facts.

Hickey, S. E., Curry, C. J., & Toriello, H. V. (2013). ACMG practice guideline: Lack of evidence for MTHFR polymorphism testing. Genetics in Medicine, 15(2), 153–156. https://doi.org/10.1038/gim.2012.165

National Institutes of Health, Office of Dietary Supplements. (n.d.). Folate: Fact sheet for health professionals.

National Library of Medicine. (n.d.). MTHFR gene. MedlinePlus Genetics.

Tsang, B. L., Devine, O. J., Cordero, A. M., Marchetta, C. M., Mulinare, J., Mersereau, P., Guo, J., Qi, Y. P., Berry, R. J., Rosenthal, J., Crider, K. S., & Hamner, H. C. (2015). Assessing the association between the methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphism and blood folate concentrations: A systematic review and meta-analysis of trials and observational studies. The American Journal of Clinical Nutrition, 101(6), 1286–1294. https://doi.org/10.3945/ajcn.114.099994