Relationship of vitamin B12 deficiency in metformin-treated type-2 diabetes with peripheral neuropathy

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Relationship of vitamin B12 deficiency in metformin-treated type-2 diabetes with peripheral neuropathy

Metformin is routinely prescribed to about 120 million diabetic patients around the world. It is the main medication in the management of type 2 diabetes mellitus (T2DM). The relationship between long-term metformin use and low vitamin B12 levels has already been delineated. But, the occurrence estimates of metformin-induced vitamin B12 deficiency depicted considerable variation among the studies. The prospects of the deficiency to cause or worsen peripheral neuropathy in type-2 diabetes mellitus (T2DM) patients has been assessed with conflicting results.

A study was done to analyze 1) the prevalence of vitamin B12 deficiency in T2DM patients on metformin; 2) the relation between vitamin B12 and peripheral neuropathy; 3) and the risk factors for vitamin B12 deficiency in these patients.

In the study, consecutive metformin-treated T2DM patients attending diabetes clinics of two public hospitals in South Africa were considered for participation. Participation included assessing vitamin B12 levels and analyzing peripheral neuropathy via the Neuropathy Total Symptom Score-6 (NTSS-6) questionnaire. The frequency of vitamin B12 deficiency (defined by concentrations <150 pmol/L) was established. People with NTSS-6 scores >6 were regarded to have peripheral neuropathy. When two variables were in the binary and continuous forms, the relationship between vitamin B12 and peripheral neuropathy was determined. Risk factors for vitamin B12 deficiency was determined by using multiple logistic regression.

As per results, among 121 participants, prevalence of vitamin B12 deficiency was 28.1 %. No difference in presence of neuropathy between those with normal and deficient vitamin levels (36.8 % vs. 32.3 %, P = 0.209) was observed. NTSS-6 scores and vitamin B12 levels were not correlated (Spearman’s rho =0.056, P = 0.54). HbA1c (mmol/mol) (OR = 0.97, 95 % CI: 0.95 to 0.99, P = 0.003) and black race (OR = 0.34, 95 % CI: 0.13 to 0.92, P = 0.033) were risk factors notably associated with vitamin B12 deficiency. The metformin daily dose (gram) revealed borderline significance (OR = 1.96, 95 % CI: 0.99 to 3.88, P = 0.053).

It was culminated that close to third of metformin-treated T2DM patients had vitamin B12 deficiency. This deficiency had no relation with peripheral neuropathy. Black race was an armored factor for vitamin B12 deficiency.

BMC Pharmacology and Toxicology
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