The MTHFR genetic error is getting more attention now.

You can have it tested:
http://www.kimballgenetics.com/tests-mthfr.html

Or you can get a homocysteine test to see if it is elevated in spite of taking folic acid. This might cost less.

So far there are 25 specific polymorphisms of the MTHFR pathway. I
This genetic failure is more common than previously thought.

It used to be very inexpensive (about $5-6 for a 100 tabs) to just take methylfolate (like it is for methylcobalamin) until the greedy drug manufacturer holding the patent, Merck, decided it would make more money by withholding sale of it to vitamin makers, like Source Naturals. They wanted to FORCE people to get the far more expensive RX only drugs, Metanx and Cerefolin.

Folinic acid is still OTC and will work in a similar way.
Source Naturals makes it also. They substituted it when the supply was cut by Merck. Folinic acid has been RX for decades at 5mg tablets and called Leucovorin to treat folate loss during certain chemo treatments. It is a very common form of bioavailable folate.