Folate analogues are medications that work like folic acid (vitamin B9) in the body. They're used to treat low folic acid levels, as part of certain cancer treatments, and to protect against the side effects of methotrexate. Folate analogues come in different forms, including oral tablets and injectable solutions. Examples include leucovorin, l-methylfolate, and levoleucovorin (Fusilev, Khapzory).