highly significantp ≤ 0.01
The seven studies in Table 1 indicated either an association of metformin use with a lower vitamin B12 concentration [ 13 , 14 , 16 , 17 , 19 , 20 , 21 ] that was highly significant ( p ≤ 0.01) or was not significantly different (432 ± 206 vs. 448 ± 219 pg/ml; p = 0.4 in one study [ 12 ].