Do not take leucovorin if you have anemia that is caused by a lack of vitamin B12.
Before taking leucovorin, tell your doctor if you are allergic to any drugs, or if you have kidney, liver, or lung disease.
Before taking leucovorin, tell your doctor if you are using fluorouracil (Adrucil), phenytoin (Dilantin), fosphenytoin (Cerebyx), ethotoin (Peganone), phenobarbital (Luminal, Solfoton), or primidone (Mysoline).
When treating an accidental overdose, leucovorin should be started as soon as possible for best effect.
To be sure this medication is helping your condition, your blood will need to be tested often. This will help your doctor determine how long to treat you with leucovorin.