MTHFR and homocysteine are linked because homocysteine builds up when the folate cycle isn't working efficiently, which can happen with MTHFR. Because of this, testing homocysteine can be a helpful way to determine whether the health changes you are making for your MTHFR gene mutation are actually effective for you. In this post, we will cover Homocysteine testing and parameters - what is normal, what isn't, and what is considered normal but maybe shouldn't be.