HSA | FSA CARDS ARE NOW ACCEPTED

Carnitine and SLC22A5 (OCTN2): What Your Results Mean for Cellular Energy

Carnitine is a small but essential molecule that helps move long-chain fatty acids into mitochondria, the parts of cells that produce energy. The SLC22A5 gene makes a transporter protein called OCTN2 that moves carnitine from the blood into cells and helps the kidneys conserve it. Variations in SLC22A5 can change how effectively cells access carnitine. That can lead to normal or even higher blood levels of carnitine while cellular availability is reduced, which matters because carnitine works inside cells—especially in heart and skeletal muscle—to support energy production, exercise performance, and metabolic balance.

How to think about these results

  • Blood carnitine is only part of the story. If transport into cells is reduced, blood levels may not reflect cellular need.
  • Diet, vitamins and minerals that support carnitine synthesis and mitochondrial function, exercise, sleep, hydration, and stress management all influence how well your body uses carnitine.
    •

Practical steps to support carnitine transport and cellular energy

  • Diet: prioritize complete proteins (meat, poultry, fish, eggs, dairy), legumes, and plant-based proteins to provide lysine and methionine, the amino acids used to make carnitine. Include a variety of vegetables, fruits, whole grains, nuts, and seeds for additional cofactors.
  • Micronutrients: ensure adequate vitamin C, vitamin B6, vitamin B12, niacin, iron, magnesium and folate to support carnitine synthesis and mitochondrial enzymes.
  • Supplements: under the guidance of your healthcare provider consider options such as L-carnitine (for cellular support), acetyl-L-carnitine (may cross into the brain more readily), and coenzyme Q10 for mitochondrial support. Start with recommended dosages and reassess effects with your clinician.
  • Exercise: combine regular aerobic activity with resistance training. Exercise increases muscle demand for carnitine and can upregulate mitochondrial capacity.
  • Sleep and stress: aim for 7 to 9 hours of quality sleep per night and use stress reduction strategies like mindfulness, breathing practices, or regular physical activity to support cellular metabolism.
  • Hydration: adequate fluid and electrolyte balance supports kidney conservation of nutrients and overall transport processes.
  • Blood testing and clinical follow up: if symptoms suggest low cellular energy (fatigue, exercise intolerance, muscle pain, heart rhythm concerns) discuss with your clinician whether targeted blood or urine testing, or trial supplementation, is appropriate.

Genetic Interpretation

Two effect alleles (TT) — slightly higher blood carnitine, possible reduced cellular uptake

If your genotype is TT at rs274567 you carry two copies of the effect allele. This pattern is associated with slightly higher serum carnitine levels. Because SLC22A5 encodes OCTN2, the transporter responsible for moving carnitine into cells and preserving it in the kidneys, certain variants can reduce how efficiently cells take up carnitine.

Key points for TT:

  • Blood carnitine may be normal or elevated, but cellular availability can be lower than expected.
  • Heart and skeletal muscle are the tissues most sensitive to carnitine transport issues because they rely heavily on fatty acid oxidation.
  • Consider focusing on measures that improve cellular uptake and mitochondrial function rather than relying solely on blood levels.

Recommended actions:

  • Nutrition: consume adequate protein sources and include foods high in vitamin C, B6, B12, niacin, iron and magnesium.
  • Supplements: discuss with your provider whether L-carnitine or acetyl-L-carnitine and coenzyme Q10 are appropriate. A monitored trial may help determine symptom response.
  • Lifestyle: prioritize aerobic and resistance exercise, sleep, hydration and stress management to enhance cellular energy use.
  • Clinical monitoring: if you experience persistent fatigue, muscle weakness, or exercise intolerance ask your clinician about targeted testing for intracellular nutrient markers or referral to a specialist.
One effect allele (CT) — slightly higher blood carnitine, possible partial transport impact

If your genotype is CT at rs274567 you carry one copy of the effect allele. This genotype is associated with slightly higher serum carnitine levels and may modestly influence OCTN2 transporter efficiency.

Key points for CT:

  • Blood levels can look normal or slightly elevated while some reduction in cellular uptake is possible.
  • Effects are generally milder than with two effect alleles but can be meaningful when combined with other risk factors such as low dietary intake or high metabolic demand.

Recommended actions:

  • Diet: maintain consistent intake of quality proteins and nutrient-dense foods that supply cofactors for carnitine production.
  • Supplements: consider discussing a conservative supplement plan with your clinician if symptoms or testing suggest suboptimal cellular energy.
  • Exercise and recovery: a balanced training program with adequate rest helps maximize mitochondrial efficiency.
  • Monitor: if you notice decreased exercise performance, prolonged recovery, or unexplained fatigue, raise these with your healthcare provider for evaluation.
Zero effect alleles (CC) — typical transporter function

If your genotype is CC at rs274567 you carry two copies of the non-effect allele. This pattern is associated with expected SLC22A5/OCTN2 function, meaning carnitine transport into cells and renal conservation typically work as intended.

Key points for CC:

  • Your transporter function is likely typical, so blood and cellular carnitine balance is generally maintained with normal diet and lifestyle.
  • Even with typical transporter function, maintaining the right nutrients and lifestyle habits supports optimal mitochondrial function and endurance.

Recommended actions:

  • Continue a balanced diet rich in quality proteins, vitamin C, B vitamins, iron and magnesium.
  • Support mitochondria with regular aerobic and resistance exercise, sleep, and stress reduction.
  • Only consider supplementation if directed by your clinician based on symptoms or specific tests.

When to talk to your healthcare provider

Contact your clinician if you have persistent fatigue, decreased exercise capacity, unusual muscle weakness, or other concerning symptoms. They can evaluate symptoms in context, order appropriate tests, and advise on whether dietary changes, supplements or specialist referral are warranted. PlexusDx provides genetic information to inform wellness decisions but does not provide medical advice. Always consult your healthcare provider before starting any new supplement, changing medications, or making major changes to your diet or exercise routine.

Summary

SLC22A5 variants can change how well carnitine moves from blood into cells. Depending on your genotype, blood carnitine may not reflect how much is available inside muscle and heart cells. Regardless of genotype, you can support carnitine function through protein-focused nutrition, adequate vitamins and minerals, consistent exercise, sleep, hydration and stress management. Discuss any concerns or consideration of supplements with your healthcare provider.