Condition
    Strong Evidence
    Effectiveness 4/5

    Vitamin B12 for Peripheral Neuropathy

    B12 deficiency is a genuinely reversible cause of neuropathy, and early repletion can restore nerve function. Late treatment often cannot.

    Overview

    B12 deficiency is one of the few genuinely reversible causes of peripheral neuropathy. Early repletion can restore nerve function; late treatment often cannot, which makes timing the most important variable on this page.
    The typical presentation is symmetrical numbness and tingling starting in the feet, sometimes with unsteadiness in the dark from dorsal column involvement. Anaemia may be absent entirely, so a normal full blood count does not rule deficiency out. Risk concentrates in long-term metformin users, people on acid suppression, those after gastric surgery, vegans without supplementation, and older adults with atrophic gastritis.

    How It Works

    B12 is a cofactor for methionine synthase, which supplies the methylation reactions that maintain the myelin sheath, and for methylmalonyl-CoA mutase. Deficiency in both pathways produces subacute combined degeneration, affecting the dorsal columns and peripheral nerves together.
    Early on the damage is demyelination, which is repairable once the cofactor is restored. If deficiency persists, axonal degeneration follows, and that is not reversible. This staging is the reason clinicians treat suspected deficiency promptly rather than waiting for confirmatory results. Methylmalonic acid accumulates as a direct consequence of the mutase block, which is what makes it a more sensitive marker of tissue deficiency than serum B12.

    Dosing & Protocol

    Oral cyanocobalamin or methylcobalamin at 1000 mcg daily replete most people with deficiency. Where pernicious anaemia or significant malabsorption is present, or neurological signs are progressing, intramuscular loading is the safer route. Continue maintenance indefinitely if the cause of malabsorption persists.

    Evidence

    No individual trials are currently linked to this pairing in our database, so no study list is displayed rather than attaching unverified citations. The account above reflects established clinical literature on B12 deficiency neuropathy and its response to repletion.

    Verified references for this pairing are being compiled and will appear here once each has been linked and checked against the claims on this page.

    Safety

    B12 has no established upper intake level and oral repletion is very well tolerated. Injections may cause local pain or, rarely, acne-like eruptions. Rapid correction of severe deficiency can drop serum potassium, which is a reason for supervision in profound cases.

    Check B12 before starting folate. Folate can normalise the blood count while nerve damage progresses, delaying diagnosis until the damage is permanent.

    Interactions & Conflicts

    Most of what matters is the list of things that cause or mask the deficiency, rather than interactions with B12 itself.
    Interacts withSeverityMechanismAction
    high
    		—Screen B12 periodically; supplement if low
    moderate
    		—Monitor status on prolonged therapy
    high
    		—Establish B12 status first
    high
    		—Avoid recreational use; disclose deficiency to anaesthetists

    References

    Verified references for this pairing are being compiled. Sources will be listed here once each has been linked to this page and checked against the claims made above.

    Frequently Asked Questions

    Medical Disclaimer

    The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.

    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.