Protocols › Vitamin B12

Vitamin B12 for nerve damage in diabetes

Goal: To improve nerve function and nerve pain in people with diabetes, as trials of vitamin B12 tested it.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 3 Nov 2026
Dose

1,000 µg a day by mouth in a 1-year trial.[1]

Form

Methylcobalamin, also called mecobalamin.[1][2]

How long

12 months.[1]

What studies found

In 90 people with type 2 diabetes and nerve damage who took metformin and had B12 below 400 pmol/L, blood B12 rose from 232 to 777 pmol/L. Nerve tests, pain and quality of life improved in the B12 group, and several nerve tests and pain got worse in the placebo group. Tests of the nerves that control the heart did not improve significantly.[1] A 2020 review of 15 trials with 1,707 people with nerve damage from diabetes or shingles found more overall improvement with methylcobalamin alone (risk ratio 1.17), but no effect on pain scores. Of the 15 trials, 11 had a high risk of bias.[2] A 2020 systematic review rated the evidence for painful nerve damage as level III. It rated the evidence for nerve pain after shingles higher, as level II.[3] A 2022 review of 7 trials in people on metformin called the effect on nerve symptoms unclear.[4]

Ask a doctor first

Numbness and tingling have many causes, and a B12 blood test can help show whether a low level is one of them.[5] In a trial of people with kidney disease from diabetes, high doses of B12 with folic acid and vitamin B6 made kidney function fall faster.[6] Ask a doctor or pharmacist before taking B12 with diabetes medicines or with kidney disease.[6][5]

References

  1. Vitamin B12 Supplementation in Diabetic Neuropathy: A 1-Year, Randomized, Double-Blind, Placebo-Controlled Trial. Didangelos T, Karlafti E, Kotzakioulafi E, Margariti E, Giannoulaki P, Batanis G, et al. Nutrients, 2021. PMID 33513879
  2. Efficacy and Safety of Mecobalamin on Peripheral Neuropathy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Sawangjit R, Thongphui S, Chaichompu W, Phumart P J Altern Complement Med, 2020. PMID 32716261
  3. B12 as a Treatment for Peripheral Neuropathic Pain: A Systematic Review. Julian T, Syeed R, Glascow N, Angelopoulou E, Zis P Nutrients, 2020. PMID 32722436
  4. The efficacy of vitamin B(12) supplementation for treating vitamin B(12) deficiency and peripheral neuropathy in metformin-treated type 2 diabetes mellitus patients: A systematic review. Pratama S, Lauren BC, Wisnu W Diabetes Metab Syndr, 2022. PMID 36240684
  5. Vitamin B12 deficiency in over 16s: diagnosis and management (NG239). National Institute for Health and Care Excellence (NICE), 2024. www.nice.org.uk
  6. Effect of B-vitamin therapy on progression of diabetic nephropathy: a randomized controlled trial. House AA, Eliasziw M, Cattran DC, Churchill DN, Oliver MJ, Fine A, et al. JAMA, 2010. PMID 20424250