How do I interpret the MTHFR results?

The “>” designation is genetic nomenclature, describing which allele is “wild type” or normal and which allele is the variant allele. The “>” symbol points to the variant allele.

For 677 C>T, C is the normal (wild type) allele and T is the variant allele.

For 1298 A>C, A is the normal (wild type) allele and C is the variant allele. 

The terms homozygous and heterozygous refer to the individual genotype or individual result and describe the extent of normalcy or variation. There are three possible combinations for each gene: homozygous wild, heterozygous variant, and homozygous variant. Compound heterozygous refers to variants that occur on different copies of different genes.

See the table below for a visual description:



Homozygous Wild

*No variant, 2 copies of normal allele

Heterozygous Variant

*1 copy of normal allele, 1 copy of variant allele

Homozygous Variant

*2 copies of a variant allele

Compound Heterozygous

*Variants that occur on different copies of genes and which may completely “knock out” gene function


*C is normal/wild type






C/T AND 1298 A/C


*A is normal/wild type





A/C AND 677 C/T

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