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.

How SLC23A1 and Vitamin C Influence Your Health

Vitamin C is an essential nutrient for skin, blood vessels, bones, immune function, and antioxidant protection. Because the body cannot make Vitamin C on its own, we rely on food and supplements to maintain healthy levels. The SLC23A1 gene makes the SVCT1 transporter protein, which helps absorb Vitamin C in the intestines and reabsorb it in the kidneys. Variations in this gene can change how well that transporter works, which may affect circulating vitamin C levels even when dietary intake appears adequate.

Why this matters

  • Lower plasma vitamin C can reduce antioxidant protection and may affect immune resilience, wound healing, and connective tissue health.
  • People with reduced transporter function may lose more vitamin C in urine and need higher or more consistent intake to maintain normal blood levels.
  • Lifestyle factors such as smoking and chronic stress also increase vitamin C needs.

Practical Diet, Supplement, Lifestyle, and Testing Recommendations

This section offers practical steps to help support optimal vitamin C status based on genotype and lifestyle. PlexusDx provides educational information about genetic predispositions and does not provide medical advice. Always consult your healthcare provider before starting supplements, changing your diet, or ordering blood tests.

Dietary guidance

  • Aim to include a variety of vitamin C-rich foods daily: citrus fruit, strawberries, kiwi, bell peppers, broccoli, Brussels sprouts, cauliflower, spinach, kale, and other leafy greens.
  • Distribute vitamin C intake across meals rather than consuming a single large dose. Regular small servings improve steady absorption and retention.
  • Prefer whole foods for additional fiber, phytonutrients, and bioavailability. Raw and lightly cooked vegetables retain most vitamin C, while prolonged high-heat cooking reduces levels.
  • If you eat little fruit or vegetables, consider adding a vitamin C-rich smoothie, chopped raw bell pepper snacks, or a salad with citrus segments to daily habits.

Supplement guidance

  • Consider a vitamin C supplement if dietary intake is inconsistent or if you have increased needs from smoking, high stress, certain chronic conditions, or frequent illness.
  • Typical supplemental doses range from 100 mg to 500 mg per day for maintenance; higher short-term doses (up to 1,000 mg) are commonly used during illness. Your healthcare provider can advise on an appropriate dose.
  • Divide larger doses across the day (for example, 500 mg twice daily) to improve absorption and reduce urinary loss.
  • Choose well-absorbed forms such as ascorbic acid or buffered formats if you have GI sensitivity. If you have kidney disease or a history of kidney stones, consult your healthcare provider before supplementing.

Lifestyle recommendations

  • Avoid smoking and reduce exposure to secondhand smoke. Smoking depletes vitamin C and increases requirements.
  • Manage chronic stress through sleep, regular exercise, mindfulness, and social support. Stress increases oxidative load and vitamin C utilization.
  • Maintain regular physical activity. Exercise supports overall antioxidant defense but may slightly increase nutrient requirements; pairing activity with vitamin C–rich foods is beneficial.
  • Stay hydrated and limit excess alcohol which can affect nutrient absorption and status.

When to test blood levels

  • Consider measuring plasma vitamin C if you have symptoms of deficiency (fatigue, easy bruising, poor wound healing), follow a restrictive diet, or have known genetic variants that reduce transporter efficiency.
  • Repeat testing after 6 to 12 weeks of dietary or supplemental intervention to confirm improvement.
  • Work with your healthcare provider to interpret results and adjust diet or supplementation safely, especially if you have kidney disease or other medical conditions.

Genetic Interpretation for rs10063949 in SLC23A1

Two effect alleles (CC)

If your genotype is CC you carry two copies of the effect allele associated with lower plasma vitamin C. Your SVCT1 transporter may be less efficient at absorbing vitamin C in the gut and reabsorbing it in the kidneys. This can lead to lower circulating vitamin C even when dietary intake seems adequate.

  • Action steps: Prioritize daily servings of vitamin C-rich whole foods across meals. Consider a daily supplement, for example 100 to 500 mg split across the day, if dietary intake is inconsistent.
  • Monitor and reduce factors that increase vitamin C needs: stop smoking, address chronic stress, and limit excess alcohol.
  • Consider measuring plasma vitamin C with your healthcare provider and re-check after 6 to 12 weeks if you begin supplementation.
One effect allele (CT)

If your genotype is CT you carry one copy of the effect allele and may have somewhat reduced efficiency of the SVCT1 transporter. This can modestly lower circulating vitamin C compared to people without the variant.

  • Action steps: Make vitamin C-rich foods a consistent part of your daily meals. Small servings several times a day help maintain steady levels.
  • If dietary intake is limited, consider a moderate supplement such as 100 to 250 mg daily, split if needed.
  • Avoid smoking and manage stress. Discuss testing with your healthcare provider only if you have symptoms or other risk factors.
No effect alleles (TT)

If your genotype is TT you have the typical version of SLC23A1 and your SVCT1 transporter is expected to function normally for vitamin C absorption and reabsorption. You are likely to maintain healthy vitamin C levels with a balanced diet.

  • Action steps: Continue eating a variety of vitamin C-rich foods daily. Supplementation is usually not necessary unless dietary intake is poor, you smoke, or you have increased needs.
  • Maintain healthy lifestyle practices to preserve vitamin C status: avoid smoking, manage stress, and eat a nutrient-dense diet.

Final reminders

PlexusDx provides educational information about genetic predispositions and does not provide medical advice. This report is intended to help you understand how a variant in the SLC23A1 gene may affect vitamin C absorption and what practical steps you can take to support healthy vitamin C status. Always consult with your healthcare provider before beginning supplements, making major diet changes, or ordering blood tests. Your provider can help personalize recommendations based on your overall health, medications, and medical history.

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 Vitamin C and SLC23A1 rs10063949

How does the SLC23A1 rs10063949 variant affect vitamin C levels?

SLC23A1 helps produce the SVCT1 transporter, which absorbs vitamin C in the intestines and reabsorbs it in the kidneys. Variations in SLC23A1 can change transporter efficiency, which may lower circulating (plasma) vitamin C even when your diet seems adequate.

What should I do if my SLC23A1 genotype is CC, CT, or TT?

CC (two effect alleles): you may have reduced SVCT1 efficiency, so prioritize vitamin C-rich whole foods daily, consider splitting a supplement (for example 100–500 mg/day) if intake is inconsistent, and address higher-need factors like smoking and chronic stress; consider checking plasma vitamin C and repeating after 6–12 weeks. CT (one effect allele): aim for consistent vitamin C foods across multiple meals; a moderate supplement (often 100–250 mg/day) may help if intake is limited; consider testing with your healthcare provider if symptoms or risk factors apply. TT (no effect alleles): transporter function is expected to be typical, so focus on a balanced diet; supplementation is usually only needed if intake is poor or needs are increased (e.g., smoking).

When should I test my plasma vitamin C, and how do I interpret it?

Consider measuring plasma vitamin C if you have possible deficiency symptoms (fatigue, easy bruising, poor wound healing), a restrictive diet, or known variants that reduce transporter efficiency. Repeat testing after 6–12 weeks of dietary and/or supplemental changes to confirm improvement. Work with your healthcare provider to interpret results and adjust safely—especially if you have kidney disease or a history of kidney stones.

What tests can help me learn more about Vitamin C and SLC23A1 rs10063949?

The Optimal Diet and Weight Loss Genetic Test delivers over 295 genetic insights related to nutrition response, body composition, metabolism, and fitness. The Diet and Nutrition 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.