What illness is a problem arising from a prescribed medical treatment?

A problem arising from a prescribed medical treatment is known as an "adverse drug reaction" (ADR). This refers to any harmful or unintended effect resulting from the use of a medication, which can range from mild side effects to serious health complications. ADRs can complicate treatment regimens, lead to medication non-adherence, and may require additional medical interventions. It's crucial for healthcare providers to monitor patients closely for these reactions.