Adverse drug reactions (ADRs) are classified into different types based on their severity. The severity of an ADR refers to the degree of harm or damage caused by the reaction. The following are the different types of ADRs based on severity: Mild ADRs: These are the least severe type of ADRs and are usually self-limiting. Mild ADRs do not require any specific treatment and usually resolve on their own. Examples of mild ADRs include nausea, headache, and mild allergic reactions. Moderate ADRs: These ADRs are more severe than mild ADRs and may require medical intervention or treatment. They may cause discomfort and can affect the patient's daily activities. Examples of moderate ADRs include severe allergic reactions, diarrhea, and dizziness. Severe ADRs: These are the most severe type of ADRs and can be life-threatening. They require immediate medical attention and may result in hospitalization or even death. Examples of severe ADRs include anaphylaxis, Stevens-Johnson Syndrome (SJS), and toxic epidermal necrolysis (TEN). Serious ADRs: These are ADRs that result in hospitalization, prolongation of hospitalization, disability, or death. Serious ADRs are usually severe in nature and require immediate medical attention. Examples of serious ADRs include renal failure, liver failure, and pulmonary embolism. Unexpected ADRs: These are ADRs that are not listed in the product label or are not expected based on the known safety profile of the drug. Unexpected ADRs can be of any severity and require immediate reporting to regulatory authorities.