HSA | FSA CARDS ARE NOW ACCEPTED

Last reviewed: May 12, 2026 Last updated: May 12, 2026

Written by: Jay Hastings , CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance. His work has included scaling healthcare startups, leading CLIA lab integrations, and helping expand consumer access to precision health tools.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

MTHFD1L and One-Carbon Metabolism: What Your Genotype Means for Methylation, Nucleotide Synthesis, and Health

The MTHFD1L gene produces a mitochondrial enzyme that plays a key role in formate production and the mitochondrial arm of one-carbon metabolism. Formate is exported from mitochondria to the cytoplasm where it helps generate 10-formyl-THF for purine and nucleotide synthesis and 5-MTHF for remethylation of homocysteine to methionine. Through this linkage, MTHFD1L influences availability of S-adenosylmethionine or SAMe, which is central to DNA methylation, epigenetic regulation, neurotransmitter production, and many detoxification pathways.

Genetic changes that reduce MTHFD1L function can limit mitochondrial formate output, creating a bottleneck in one-carbon supply. That can slow the methylation cycle and stress nucleotide production, especially during periods of high demand such as rapid cell growth, pregnancy, inflammation, or low nutrient intake. Conversely, typical MTHFD1L activity helps keep nucleotide synthesis and methylation running efficiently, supporting genomic stability and healthy cell replication.

How we use this information

This article explains what different genotypes at rs11754661 mean for MTHFD1L activity, what health considerations may be relevant, and practical diet, supplement, lifestyle, and testing suggestions you can discuss with your healthcare provider. PlexusDx does not provide medical advice. Always consult your healthcare provider before making changes to diet, supplements, or medications.

Genetic interpretation

2 effect alleles (AA) — reduced MTHFD1L activity

The AA genotype at rs11754661 has been associated with reduced MTHFD1L function and potentially lower mitochondrial formate output. Reduced formate can narrow the flow of one-carbon units to the cytosolic folate cycle and lower production of 5-MTHF, which may limit remethylation of homocysteine to methionine and reduce SAMe availability. This can affect DNA methylation, nucleotide synthesis, and processes that rely on methyl donors.

Considerations

  • Maintain strong folate and B12 status to support downstream methylation.
  • Support serine and glycine availability since mitochondrial serine catabolism helps supply formate.
  • Monitor homocysteine if clinically indicated to assess methylation stress.
  • Focus on nutrient-dense diet and lifestyle practices that support mitochondrial health.
1 effect allele (AG) — moderately altered MTHFD1L activity

The AG genotype is associated with a moderate change in mitochondrial formate production. In everyday conditions you may function normally, but during higher metabolic demand or with low folate intake the limited one-carbon supply could become more relevant.

Considerations

  • Ensure sufficient dietary folate, B12, and amino acids that feed one-carbon metabolism.
  • Support serine and glycine flux and consider lifestyle steps to protect mitochondrial function.
  • Be attentive to periods of increased demand such as pregnancy, intense training, or illness.
0 effect alleles (GG) — typical MTHFD1L activity

The GG genotype is associated with expected or typical MTHFD1L activity and steady mitochondrial formate export. With this genotype the folate cycle generally receives normal one-carbon input for nucleotide synthesis and methyl-donor regeneration, assuming adequate nutrient status and mitochondrial health.

Considerations

  • Maintain balanced intake of folate, B12, and serine/glycine to support ongoing methylation and nucleotide needs.
  • Follow general healthy lifestyle practices to preserve mitochondrial and overall metabolic resilience.

Dietary recommendations

  • Prioritize natural folate rich foods: dark leafy greens, asparagus, Brussels sprouts, lentils, chickpeas, and liver if appropriate. Natural folate supports 5-MTHF and folate cycle flux.
  • Include vitamin B12 sources: seafood, fish, poultry, eggs, dairy, or fortified foods. If you follow a vegetarian or vegan diet consider B12 supplementation after testing.
  • Boost serine and glycine precursors: protein-rich foods such as poultry, eggs, fish, soy, legumes, and seeds provide amino acids that feed one-carbon metabolism. Bone broths and gelatinous cuts supply glycine.
  • Consume choline and betaine containing foods: eggs, soy, broccoli, quinoa, and beets. Choline and betaine can donate methyl groups and support homocysteine remethylation.
  • Limit excess alcohol: alcohol impairs folate absorption and methylation processes.

Supplement recommendations (discuss with your provider)

  • Folate as methylfolate (5-MTHF) or a balanced folate form: supports cytosolic folate pools and remethylation. People with limited mitochondrial formate output may benefit from ensuring adequate active folate availability.
  • Vitamin B12 as methylcobalamin or hydroxocobalamin: supports methionine synthase and remethylation of homocysteine.
  • B-complex and cofactors: B2 riboflavin and B6 pyridoxine support enzymes in one-carbon metabolism and transsulfuration pathways.
  • Betaine (trimethylglycine) or choline: alternative methyl donor pathways can help maintain methylation when folate dependent remethylation is challenged.
  • Mitochondrial support nutrients: coenzyme Q10, alpha lipoic acid, magnesium, and adequate dietary protein may support mitochondrial function and one-carbon flux indirectly.
  • Do not self-prescribe high dose supplements without medical oversight. Discuss appropriate forms and dosages with your healthcare provider, especially during pregnancy, lactation, or when taking medications.

Lifestyle and testing considerations

  • Measure plasma homocysteine and B12/folate status if you or your clinician are concerned about methylation stress. Trends over time are often more informative than a single snapshot.
  • Prioritize regular physical activity and resistance training which support mitochondrial biogenesis and metabolic flexibility.
  • Get consistent, restorative sleep. Sleep deprivation impairs metabolic and mitochondrial function.
  • Manage chronic stress through behavior strategies such as mindfulness, breathing exercises, or counseling. Chronic stress can raise metabolic demand and alter methylation requirements.
  • Avoid smoking and reduce exposure to environmental toxins that increase demand on methylation and detoxification pathways.
  • During pregnancy or planned conception, coordinate with your healthcare provider to ensure appropriate folate and B12 support given increased nucleotide and methylation demands.

When to talk to your healthcare provider

  • If lab tests show elevated homocysteine, low B12, or low folate you should follow up with your clinician to determine cause and treatment.
  • If you are pregnant, trying to conceive, or on medications that affect folate or B12 status discuss personalized supplementation strategies.
  • If you plan to begin supplements such as methylfolate, high dose B12, betaine, or mitochondrial-targeted therapies consult your healthcare provider to check for interactions and appropriate dosing.

Final notes and disclaimer

This information is educational and intended to help you understand how MTHFD1L variation can affect one-carbon metabolism, methylation, and related nutrient needs. PlexusDx does not provide medical advice. Always consult your healthcare provider before starting or stopping supplements, making significant dietary changes, or adjusting medical treatments. Your healthcare provider can interpret genetic results in context of your medical history, current labs, medications, and personal goals.

If this genetic variant is present in your PlexusDx results, the following tests and reports are commonly used to explore it further:

🧬 Genetic Tests:

🧪 Blood Tests:

📄 Genetic Report:

Frequently Asked Questions About Formate Metabolism and MTHFD1L rs11754661

What does the MTHFD1L rs11754661 genotype mean for methylation and SAMe?

The MTHFD1L gene helps supply one-carbon units from mitochondria to the cytoplasm, supporting production of 5-MTHF for remethylating homocysteine to methionine and helping maintain SAMe availability. With the rs11754661 AA genotype, reduced MTHFD1L activity may lower mitochondrial formate output, potentially slowing the methylation cycle and stressing methyl-donor availability—especially during higher-demand periods. AG may reflect a moderate shift, while GG is associated with typical MTHFD1L activity when nutrient status is adequate.

How can one-carbon metabolism differ between AA, AG, and GG at rs11754661?

AA (two effect alleles) is linked to reduced MTHFD1L function and potentially lower mitochondrial formate export, which can narrow one-carbon flow for nucleotide synthesis and remethylation of homocysteine. AG is associated with a moderate alteration, where effects may be more noticeable during folate-limited states or increased metabolic demand. GG (no effect alleles) is associated with typical MTHFD1L activity, supporting steady one-carbon input for methylation and nucleotide needs if folate, B12, and mitochondrial health are adequate.

What diet, supplements, and labs are commonly recommended to support methylation with MTHFD1L variation?

Diet priorities often include folate-rich foods (e.g., leafy greens, asparagus, lentils), vitamin B12 sources (especially important for vegetarian/vegan diets), and amino-acid precursors like serine and glycine (from protein foods, eggs, fish, legumes; glycine from gelatinous cuts/bone broths). Choline and betaine sources (eggs, soy, broccoli, quinoa, beets) can support alternative methyl-donor pathways. Supplements—when appropriate—may include methylfolate (5-MTHF), B12 (methylcobalamin or hydroxocobalamin), B-complex cofactors (B2, B6), and beta-in/ choline under clinician guidance. Labs commonly discussed include plasma homocysteine plus B12/folate status, ideally tracked over time, and results should be reviewed with a healthcare provider before starting or changing supplements, especially in pregnancy or when on medications.

What tests can help me learn more about Formate Metabolism and MTHFD1L rs11754661?

The Genetic Methylation Test delivers over 300 genetic insights related to methylation, detoxification, and nutrient processing. The Methylation Pathway Genetic Report translates your results into personalized, actionable guidance. Your healthcare provider can also recommend targeted blood tests based on your specific pathway results and health history to complement your genetic insights with current biomarker data.

Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance. References are included at the end of the article when scientific, medical, or health-related claims are discussed.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.