Homo, Hetero, Huh?

So you got your genetic test results back and are confused as to what all these complicated-sounding science-y words mean. There's the C677T variant and then the A1298C. You can be heterozygous, homozygous, or even compound! It can be a bit overwhelming, but have no fear. This post will break it down for you in a way that's simple to understand.

C677T vs. A1298C

First thing's first...there are two primary types of MTHFR genetic variants: C677T and A1298C. Each of these represent a specific location in the MTHFR gene where the DNA code varies a bit from the general population. While it is technically possible to have an MTHFR variant that is not one of these two possibilities, it is highly unlikely. C677T and A1298C are the two variants that are the most common and well-understood.

While both of these combinations of letters and numbers represents a specific variant that the MTHFR gene could present with, they manifest a bit differently from each other when it comes to health. C677T is associated with more health problems because it impairs methylation to a greater degree than A1298C. On the other hand, A1298C is connected to more neurotransmitter and mental health issues.

However, it's important to note that these are just general trends. This does not mean that A1298C doesn't have a significant impact on methylation or that C677T can't impair mental health. Each variant simply has its area of most marked damage. Beyond which type of genetic variant you have, the amount of impact it will have depends on how many copies you carry. That's where it's important to understand if you're heterozygous, homozygous, or compound...

Heterozygous vs. Homozygous vs. Compound

Everyone carries two copies of the MTHFR gene, inherited from each of their biological parents. To be heterozygous means that you inherited one MTHFR gene with a variant and one "typical" MTHFR gene without a deviation. To be homozygous means that you inherited two MTHFR variants. In other words, both of your MTHFR genes contain a variant in the DNA code. As you would probably imagine, being homozygous is associated with more health problems than being heterozygous because both MTHFR genes contain a variant. This means that methylation will be impacted to a more severe degree.

To complicate matters even further, it's also possible to have both the C677T and A1298C variants! In such a case, a person would be considered to have a compound diagnosis. If one copy of each variant is present, then the diagnosis would be compound heterozygous. If two copies of each are present, the diagnosis would be compound homozygous. A compound homozygous diagnosis would cause the most severe impact on methylation and health of all. Such a circumstance is very rare, but not impossible.

The Bottom Line

While there are general trends as to which diagnosis causes the most health problems, no MTHFR variant diagnosis is insignificant. Regardless of which variant you may have or how many copies you carry, I highly suggest making strategic changes that will accommodate and optimize your genetics.


To take a deeper, guided dive into how to thrive with an MTHFR variant, check out Hey MTHFR Academy. This 16-week online course will give you the tools you need to harness the power of epigenetics and befriend your MTHFR gene.