Codeine NHS warning over ‘unpleasant’ side effect for more than 1 in 100 peopleGuidance from the NHS has highlighted a common side effect for people who take codeine for pain reliefView Image Codeine can cause a range of common side effects (Image: Getty Images)In the UK, over 74 million controlled drugs were prescribed in England alone in 2024. ‌According to the NHS, codeine is often used to treat pain after a patient has undergone an operation or suffered an injury. NHS guidance highlights that more than one in 100 people could suffer from symptoms such as constipation, feeling sick, confusion, tiredness, dizziness, and headaches. According to data from the NHS, less than one in 100 people may experience symptoms such as muscle stiffness and symptoms associated with low blood pressure, such as feeling dizzy or tired. NHS guidance highlights that this is especially the case if you begin to experience side effects like constipation.