Vitamin B12 profile assesses vitamin B12 status at the time of sample collection. We will use the Active-B12 (holotranscobalamin, holoTC), total serum B12 and methylmalonic acid (MMA) tests for this assessment. The Active-B12 test measures the biologically active fraction of vitamin B12 which is utilised by cells. Serum B12 measures all B12 forms present in blood (active and inactive). Values above our cut-offs for these tests normally suggest good vitamin B12 status. MMA is the functional test (reflects utilization of B12 by tissues/cells) for vitamin B12 deficiency. Elevated MMA concentration can suggest vitamin B12 deficiency or B12 being not utilized well by cells. Please note that MMA can be also elevated independently of vitamin B12 deficiency e. g. in thyroid disease, renal impairment, some genetic conditions, intestinal bacterial overgrowth or hemoconcentration. Antibiotics treatment can lower MMA.
In exceptional circumstances e.g. in view of other results (if requested), issues with sample volumes or highly abnormal results, we may also request plasma homocysteine to further support the assessment of vitamin B12 status.