Hi Dear user ! I have gone through your questions and i understand your concern! One of the most serious and most often side of this medication is infection. This drug block an enzyme that play a major role in the immunity system in the end your immunity system will function less. It s a choice the we make when methotrexate is not successful. In this condition viruses , bacteria , fungus or others ,take advantage and cause infection ( pneumonia, urinary tract infections, Herpes reactivation if you have the virus in your body, cellulitis ...) be aware of these symptoms : - cough, sore throat, sneezing,stuffy or runny nose,, fever, chest pain, difficult breathing, burning ,difficult or painful urination, or any other sign of infection. Allergic reaction: difficult breathing , , rapid breathing .rash Liver problems : Elevated liver test ( ALT/AST)., dark urine or stools , itching, yellow skin or eyes. Gastrointestinal problems: diarrhea, ,nause,vomiting , abdominal pain , .. Hypertension, dehydration, headache, dizziness, sleeping problem, muscles pain...anemia If you have any of the symptoms you must go to your local doctor( he /she will stop the medication ) I would suggest to blood test every 3 month to check your liver, white blood cells , red blood cells, cholesterol. Wish these help. If you have any other questions please feel free to ask me .