Supplements
vitamin B12 causes small-fibre neuropathy
Part of: 🧪 Vitamin B12
📅 Last reviewed: 2026-07-15 ⓘ
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: Population patterns (Observational)
How the studies fall
What the evidence shows
Vitamin B12 deficiency causes small-fibre neuropathy (reduced IENFD). A competing/additive testable hypothesis for unexplained neuropathy — cheaply confirmable or excludable with B12 + MMA + homocysteine (serum B12 reads high on methyl-B12 supplementation, so MMA/homocysteine are the informative tests).
The evidence (5)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Güneş HN, et al. 2018 · Int J Neurosci | observational | supports | moderate | B12-deficient patients with neuropathic pain had lower IENFD (~3.35 vs 6.20, p<0.001) than those without → B12 deficiency linked to small-fibre loss. |
| Khan 2012 2012 · Muscle Nerve | observational | supports | low | [FT-verified] Khan 2012 NLD-SFN phenotyping; B12 one of many assoc not B12-specific; weak/peripheral |
| Issi 2025 · Neurol Res Pract | observational | supports | low | [FT-verified] 2025 obs n=28 B12-deficient subclinical SFN by electrophysiology; associative |
| d10-56238-arev8n5-023 2026 · Aracê. | observational | supports | low | Case report, n=1 (63-year-old woman) with SFN (hand paresthesia, burning leg pain) confirmed by absent pain-related evoked potentials (PREP); serum B12 111 pg/mL. After B12 replacement therapy, B12 rose to 304 pg/mL and PREP responses norma |
| de Greef 2018 · Eur J Neurol | observational | supports | low | [FT-verified] de Greef 2018 large SFN cohort B12 deficiency enrichment; associative not causal |
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