Leucovorin calcium 50mg Injection contains the active substance Leucovorin calcium which is chemically related to a vitamin called folic acid. It belongs to the class folic acid analogs. It is used to prevent the harmful effects of methotrexate medicine when treating certain types of cancer. It is also used to treat people who have accidentally overdosed on methotrexate medicine or medications that belong to a similar class. It is also used with other anticancer medications to treat colorectal cancer (cancer that begins in the colon or rectum). Other uses include treating anemia caused by low levels of folic acid in the body. Do not take Leucovorin calcium 50mg Injection if you are allergic to Leucovorin calcium, calcium folinate, or any other ingredients of this medicine if you have certain types of anemia (pernicious anemia or megaloblastic anemia) where vitamin B12 is deficient. Before initiating the treatment, inform your physician if you have anemia, kidney, heart, or liver problems. Inform your physician if you are using any medications for treating seizures. Notify your physician if you face any symptoms of wheezing or trouble breathing, skin rash, itching or hives, or swelling in the lips, face, or tongue.