What will happen if i get a piercing while on mtx?

Usually nothing: If Methotrexate (mtx) increases infection risk, it is minimal. Some published studies even show no increased risk. However, if mtx is taken for rheumatoid arthritis (ra), there is an increased infection risk due to the ra. If the RA is well controlled, some patients choose to skip mtx for a week while they get pierced (not usually necessary). Sterile piercing technique is far more important!