So many people are confused, about whether Codeine is legal or not. After the study, it concluded that; Codeine is a legal medication with FDA certification. But it's legal for people who are suffering from various pain; not for others. It completely removes pain after some days of use. The doctor suggested; that in case you miss a dose in a day, do not take an overdose at the same time. It causes side effects, dry mouth, headache, vomiting, stomach pain, red marks in the body, mood swings, etc.