Another warning about metformin for diabetes and Vitamin B12

Judging from the tone of this paper just published in the journal Diabetes Care, there are still too few professionals and lay people alike who are not aware that Vitamin B12 must be attended to when taking the type 2 diabetes drug metformin. The authors focus on the varying severity of diabetic neuropathy and observe:

"Long-term use of metformin is associated with malabsorption of vitamin B12 (cobalamin [Cbl]) and elevated homocysteine (Hcy) and methylmalonic acid (MMA) levels, which may have deleterious effects on peripheral nerves."

It won't surprise any readers of these posts that their data showed...

"Metformin-treated patients had depressed Cbl levels and elevated fasting MMA and Hcy levels. Clinical and electrophysiological measures identified more severe peripheral neuropathy in these patients; the cumulative metformin dose correlated strongly with these clinical and paraclinical group differences."

Their conclusion:

"Metformin exposure may be an iatrogenic cause for exacerbation of peripheral neuropathy in patients with type 2 diabetes. Interval screening for Cbl deficiency and systemic Cbl therapy should be considered upon initiation of, as well as during, metformin therapy to detect potential secondary causes of worsening peripheral neuropathy."

Remember, when taking metformin you need to check your B12 levels, not by measuring it in the serum (blood) which is unreliable, but with methylmalonic acid in the blood or urine (not perfect but better) and keeping an eye on homocysteine.