If you suffer significant hair loss, like I did, while taking mtx, there could be a genetic reason. A recent DNA test revealed that I have the MTHFR A1286C gene mutation (homozygous, for me--from both parents). This gene mutation is apparently fairly common especially in European ancestry. People with this mutation cannot process synthetic folic acid. So all the synthetic folic acid supplements in the world would not have made any difference. If you are on mtx and hair loss is a problem, ask your doctor about the MTHFR mutation. It could be the culprit!