Vitamin B12 for Neuropathy
Vitamin B12 may improve nerve symptoms when blood levels are deficient or borderline, but the trustworthy evidence for this is now limited to a single major trial after removing several fabricated citations; for people with normal B12, benefit for general or diabetic neuropathy is unproven. Get tested before supplementing.
Why this grade7-layer evidence engine
The grade is downgraded to C (limited evidence) because most of the citations originally used to justify tier B were fabricated or mismatched to unrelated papers (on radiotherapy, statins, insect ecology, and behavioral economics). After verifying against PubMed, the strongest real study is a 12-month, placebo-controlled RCT in metformin-treated type 2 diabetics with confirmed B12 deficiency (blood level <400 pmol/L): Didangelos et al. 2021 (PMID 33513879, n=90) found that 1000 mcg/day oral methylcobalamin improved sensory nerve conduction, vibration perception, pain score, and quality of life (p<0.001 for most measures), though it did not improve cardiovascular autonomic reflex tests.
A 2020 systematic review of 24 studies (Julian et al., PMID 32722436) found some evidence for B12 in post-herpetic neuralgia and painful peripheral neuropathy, but concluded B12 does not prevent chemotherapy-induced peripheral neuropathy. Three other citations previously used to support this claim (attributed to a 'Yang 2023 MA of 14 RCTs', a 'deficiency-neuropathy review', and an 'earlier review') turned out to resolve to unrelated papers and could not be replaced with a verified real source, so those specific numbers have been removed rather than repeated.
Regulators and clinics draw the same line. The NIH Office of Dietary Supplements states B12 has 'no beneficial effect... in the absence of a nutritional deficit,' and the American Academy of Neurology and ADA (L5e) recommend B12 only when lab-confirmed deficiency is the cause, not as a general neuropathy treatment. Mayo and Cleveland Clinic warn that untreated deficiency causes nerve damage but do not endorse B12 for non-deficient patients. Practical takeaway: test serum B12 (and MMA) first; if you are not deficient, B12 is unlikely to fix the problem and is not a substitute for first-line care.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.558
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (2 篇 > 0 negative)
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status