PROBLEM TO BE SOLVED: To provide a homocysteine level inhibitor which can be administered safely and simply for a long period of time and which is used for lowering and preventing from increase of plasma total homocysteine levels when MTHFR gene type is a mutation homo-type.SOLUTION: The invention provides a homocysteine level inhibitor which consists of dry powders of a cell wall crushed material of Chlorella pyrenoidosa in which 95% or more of the cell wall is crushed, the inhibitor being used for lowering and preventing from increase of plasma total homocysteine levels when MTHFR gene type is a mutation homo-type. Plasma total homocysteine levels can be effectively lowered or can be effectively prevented from increasing by oral administration of the homocysteine level inhibitor in the amount that includes folic acid in the amount of at least 42% by weight of recommended dose of folic acid when MTHFR gene type is a mutation homo-type.SELECTED DRAWING: None
