The amount of a bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase, mitochondrial when measured in blood. The trait is level of bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase, mitochondrial in blood (Ontology of Biological Attributes term OBA_2050762). Also known as: blood bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase, mitochondrial amount.