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.

Folate, MTHFR, and What Your Genes Mean for Methylation

Folate is a cornerstone nutrient for methylation, the biochemical system that supports DNA maintenance, neurotransmitter production, lipid metabolism, and detoxification. In the body folate is converted into its active form 5-methyltetrahydrofolate (5-MTHF). That active folate donates a one-carbon unit to convert homocysteine into methionine, replenishing S-adenosylmethionine (SAMe) — the universal methyl donor used throughout the body.

The MTHFR enzyme helps convert 5,10-methylene-THF into 5-MTHF. When MTHFR activity is reduced, the supply of active folate can be limited, which can slow remethylation and impact overall methylation capacity. Compared with synthetic folic acid, 5-MTHF is already active and bypasses certain enzymatic steps, so it can be especially helpful when MTHFR or DHFR activity is lower.

Why this matters for health

  • Low active folate or impaired remethylation may raise homocysteine, a marker associated with cardiovascular and other metabolic risks.
  • Reduced methylation capacity can affect energy, mood, neurotransmitter balance, and detoxification pathways.
  • During pregnancy, adequate active folate is essential for optimal fetal development and to reduce neural tube risk.

Tests and monitoring to consider

  • Plasma homocysteine — evaluates remethylation performance.
  • Serum folate and red blood cell folate — show short- and long-term folate status.
  • Vitamin B12 (serum and, if needed, methylmalonic acid) — B12 is required for remethylation.
  • Riboflavin (B2) status may be relevant because it is a cofactor for MTHFR activity.
  • Talk with your healthcare provider before ordering tests or starting supplements.

Practical diet, supplement, and lifestyle recommendations

These suggestions are intended to support methylation and general health. PlexusDx does not provide medical advice. Always consult your healthcare provider before starting new supplements, changing medications, or making major diet changes.

Diet

  • Eat folate-rich whole foods daily: dark leafy greens (spinach, kale), legumes (lentils, chickpeas, beans), beets, asparagus, and liver if you eat animal products.
  • Include B12 sources if you consume animal products: fish, meat, eggs, and dairy. If you follow a vegetarian or vegan diet, talk to your clinician about B12 supplementation.
  • Choose whole grains and fortified foods when appropriate to help maintain folate and B-vitamin intake.
  • Support gut health: a balanced microbiome helps nutrient absorption. Prioritize fiber, fermented foods, and adequate hydration.

Supplements to discuss with your clinician

  • Low-dose methylfolate (L-5-MTHF) when active folate support is needed. Dosage and necessity depend on genotype, labs, and clinical context.
  • Methylcobalamin (active B12) to pair with methylfolate and support remethylation.
  • Riboflavin (vitamin B2) to support MTHFR enzyme function.
  • A balanced B-complex may help ensure adequate cofactor status for methylation and related pathways.
  • Avoid high-dose folic acid supplements without clinical indication, especially if functional folate metabolism is a concern; discuss with your provider.

Lifestyle

  • Manage stress: chronic stress can increase nutrient demand and affect methylation. Use sleep hygiene, mindfulness, and regular physical activity.
  • Regular moderate exercise supports cardiovascular health and metabolic flexibility.
  • Avoid smoking and excess alcohol, both of which can disrupt methylation and nutrient status.
  • Maintain a healthy body weight and monitor cardiovascular risk factors as recommended by your provider.

Genetic interpretation for MTHFR rs1801133

Two effect alleles (AA) — reduced MTHFR activity

If you have the AA genotype for rs1801133, you carry two copies of the effect allele and typically have notably reduced MTHFR enzyme activity, often around a 70 to 80 percent reduction. That means your conversion of folate into the active 5-MTHF form can be much less efficient. When active folate is limited, homocysteine may rise and methylation capacity can be compromised.

Practical considerations

  • Diet: Prioritize folate-dense foods such as dark leafy greens, legumes, beets, and if tolerated, small amounts of liver.
  • Supplements: Discuss a low-dose methylfolate (5-MTHF) supplement with your clinician. Use alongside adequate vitamin B12 (methylcobalamin) and riboflavin (B2) to support the pathway.
  • Testing: Consider checking homocysteine, serum and red blood cell folate, and B12 before and after interventions.
  • Life stage: During pregnancy or when planning pregnancy, speak with your provider urgently about folate form and dose to support fetal development.
One effect allele (AG) — moderately reduced MTHFR activity

If you have the AG genotype for rs1801133, you carry one copy of the effect allele and typically have moderately reduced MTHFR function, often around a 40 percent decrease. Your body may produce active 5-MTHF more slowly and may rely more on supportive cofactors like riboflavin and B12.

Practical considerations

  • Diet: Keep folate intake steady with leafy greens, legumes, and fortified whole grains. A balanced intake usually supports normal function.
  • Supplements: If tests or symptoms suggest suboptimal folate or elevated homocysteine, discuss a low-dose methylfolate and riboflavin with your clinician. Methylcobalamin is recommended if B12 status is suboptimal.
  • Monitoring: Check homocysteine if you have cardiovascular risk factors or symptoms that might relate to methylation.
  • Stress and nutrition: Under periods of illness, high stress, or poor diet, your need for active folate and B vitamins may be higher.
No effect alleles (GG) — typical MTHFR function

If you have the GG genotype for rs1801133, you carry two copies of the non-effect allele and are likely to have typical MTHFR function. Your body usually converts dietary folate to active 5-MTHF effectively, supporting normal homocysteine regulation and methylation processes.

Practical considerations

  • Diet: Maintain a folate-rich diet with leafy greens, legumes, beets, and fortified grains.
  • Supplements: Routine B12 and B2 intake through diet or a standard B-complex can help if your diet is low in animal products.
  • Monitoring: Routine screening is usually not required unless symptoms or other health conditions suggest otherwise.

PlexusDx does not provide medical advice. The information here is educational about genetic predispositions and potential nutritional strategies only. Always consult your healthcare provider to interpret your genetic results in the context of your medical history, current medications, lab results, and life stage before starting supplements or treatment plans.

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 Cofactors and Folate MTHFR rs1801133

What does the MTHFR rs1801133 genotype mean for methylation and homocysteine?

MTHFR rs1801133 affects how efficiently your body converts folate into the active form 5-MTHF, which supports remethylation (homocysteine to methionine) and replenishes SAMe, the body’s universal methyl donor. AA (two effect alleles) typically has notably reduced MTHFR activity and may lead to higher homocysteine and reduced methylation capacity. AG (one effect allele) usually shows a moderate reduction, while GG (no effect alleles) is associated with typical MTHFR function.

Which lab tests are most useful to monitor methylation if I have an MTHFR rs1801133 effect allele?

Common monitoring includes plasma homocysteine to evaluate remethylation performance; serum folate and red blood cell folate to assess short- and long-term folate status; and vitamin B12 testing (serum, and methylmalonic acid if needed) because B12 is required for remethylation. Riboflavin (B2) status may also be relevant because it supports MTHFR activity. Always review test choices with your healthcare provider before ordering labs or starting supplements.

How can I support methylation with diet or supplements based on MTHFR rs1801133?

To support methylation, focus on folate-rich whole foods daily (dark leafy greens, legumes, beets, asparagus, and liver if you eat animal products) and ensure adequate B12 intake if you consume animal products (fish, meat, eggs, dairy). If you’re vegetarian or vegan, discuss B12 supplementation with your clinician. If supplementation is appropriate, clinicians may consider low-dose methylfolate (L-5-MTHF) alongside methylcobalamin (active B12) and riboflavin (B2). Pairing cofactors matters because B12 and B2 support the pathway, and high-dose folic acid is often discouraged without a clear clinical indication.

What tests can help me learn more about Cofactors and Folate MTHFR rs1801133?

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.