The order of potential (again, note that each person's severity can be different)
SEVERITY----> MOST to LEAST:

    1. C677T & C677T (Two C Copies - C677T Homozygous)

    2. C677T & A1298C (One Copy of Each The C & A - Compound Heterozygous)

    3. C677T (One C Copy - C677T Heterozygous)

    4. A1298C & A1298C (Two A Copies - A1298C Homozygous)

    5. A1298C (One A Copy - A1298C Heterozygous)

 

Source: MedHelp.org/posts/MTHFR-Methylenetetrahydrofolate-reductase