Vitamin B12 for nerve damage in type 2 diabetes
What it found
In 90 people with type 2 diabetes and nerve damage, taking 1000 micrograms of vitamin B12 daily for a year raised B12 levels and improved several nerve and pain measures.
The authors say this dose may be worth recommending for patients with B12 levels below 400 pmol/L.
What they found
Studies in people
Vitamin B12 levels
In the B12 group, levels rose from 232.0 pmol/L at the start to 776.7 pmol/L after one year. In the placebo group, levels stayed about the same.
Nerve function tests
Sural nerve conduction velocity, sural nerve action potential, and vibration perception threshold all improved in the B12 group. These measures got worse in the placebo group.
Pain and quality of life
Pain score and quality of life improved in the B12 group. Pain score got worse in the placebo group.
Sweat gland function
Electrochemical skin conductance in the feet improved in the B12 group. This test checks how well the small nerves that control sweating work.
Autonomic nerve tests
The cardiovascular autonomic reflex tests and the Michigan Neuropathy Screening Instrument Examination did not improve significantly in the B12 group. The authors note the placebo group showed a trend toward worsening on some autonomic measures.
Side effects
No adverse events suspected or possibly related to the B12 tablet were reported.
What the authors conclude
“The treatment of patients with DN with 1 mg of oral methylcobalamin for twelve months increased plasma B12 levels and improved all neurophysiological parameters, sudomotor function, pain score, and QoL, but it did not improve CARTS and MNSIE.”
Also in their conclusions
- They conclude that treating patients with diabetic neuropathy with 1 mg of oral methylcobalamin for twelve months increased plasma B12 levels and improved all neurophysiological parameters, sudomotor function, pain score, and quality of life, but it did not improve cardiovascular autonomic reflex tests or the Michigan Neuropathy Screening Instrument Examination.
- They say it is reasonable to recommend B12 supplementation in every patient with diabetic neuropathy and B12 levels below 400 pmol/L.
- They advise that future studies need to address whether B12 helps in the absence of deficiency, whether it prevents neuropathy, and which forms of neuropathy improve most.
How it was done
The authors wanted to know whether normalising vitamin B12 levels on its own improves diabetic neuropathy, since earlier studies either gave B12 with other supplements or had blood sugar changes that made B12's own effect unclear.
They randomly assigned 90 adults with type 2 diabetes, who had taken metformin for at least four years and had both peripheral and autonomic nerve damage, to take either 1000 micrograms of oral methylcobalamin or a placebo daily for 12 months. All patients had vitamin B12 levels below 400 pmol/L and stable blood sugar control.
What it can’t tell you
- This trial was done in one diabetes centre in Greece with Caucasian patients, so the results may not apply to other groups.
- The study lasted one year, so it cannot show whether the improvements last longer or whether B12 prevents nerve damage from developing.
- The trial cannot show whether B12 helps people who already have normal B12 levels.
Who paid
- Conflicts
- The authors declare no conflict of interest. The pharmaceutical company providing the supplement, had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
- Authors work at
- Aristotle University of Thessaloniki, Greece; University General Hospital of Thessaloniki ''AHEPA'', Greece; Royal Hallamshire Hospital, UK
The paper
- Title
- Vitamin B12 Supplementation in Diabetic Neuropathy: A 1-Year, Randomized, Double-Blind, Placebo-Controlled Trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Didangelos T, Karlafti E, Kotzakioulafi E, et al (2021). Vitamin B12 Supplementation in Diabetic Neuropathy: A 1-Year, Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients. doi:10.3390/nu13020395Free full textPubMed 33513879DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error