What Are Examples of Adverse Events? Your Guide to Patient Safety

October 2, 2025 •

4 min read

According to the World Health Organization, around 1 in 10 patients are harmed in healthcare, with adverse events being a leading cause. This guide explores what are examples of adverse events and the critical importance of preventing them in all medical settings.

Quick Summary

Adverse events include any unintended and harmful occurrence caused by medical intervention, from medication and surgical errors to hospital-acquired infections and patient falls.

Key Points

Medication Mistakes: Errors in prescribing, dispensing, or administering drugs are frequent adverse events.
Surgical Errors: Operating on the wrong site or leaving an object inside are severe surgical adverse events.
Infections: Hospital-acquired infections, such as CLABSIs and CAUTIs, represent a significant and often preventable category of adverse events.
Patient Falls: Unplanned falls in a healthcare setting can cause serious injury and are considered adverse events.
Diagnostic Failures: Delays or inaccuracies in diagnosis can lead to delayed or inappropriate treatment, causing patient harm.
Reporting Is Key: The analysis of reported adverse events is crucial for identifying systemic issues and improving patient safety.

Understanding Adverse Events

An adverse event is an untoward medical occurrence that results in harm to a patient as a result of medical care, rather than the underlying disease process. These events can prolong a patient’s stay, cause permanent harm, or even contribute to death. They can be preventable or unpreventable, and range widely in severity.

Adverse Events vs. Side Effects vs. Sentinel Events

It's important to distinguish between these related, but distinct, terms. While all side effects and sentinel events can be types of adverse events, the terms carry different connotations and reporting requirements.


Term	Description	Examples
Adverse Event	Any harm resulting from medical care.	Medication errors, patient falls, healthcare-associated infections.
Side Effect	An expected, but often unintended, effect of a drug or treatment.	Nausea from chemotherapy, drowsiness from allergy medication.
Sentinel Event	A serious, unexpected adverse event involving death or serious physical or psychological injury.	Wrong-site surgery, patient suicide in a healthcare facility.

Common Examples of Adverse Events in Healthcare

Adverse events can occur at any stage of care, from a routine check-up to complex surgery. Here are some of the most common categories and examples.

Medication Errors

Medication-related errors are among the most frequently reported adverse events. These errors can occur at various points in the medication process.

Wrong Dose or Medication: Administering an incorrect dose or the wrong medication entirely. Distractions during preparation or similar-looking drug names can be contributing factors.
Wrong Route of Administration: Giving medication through the wrong route, such as an oral medication intravenously.
Adverse Drug Reactions (ADRs): This can include allergic reactions or other unintended, harmful responses to a medication, though the line between side effect and ADR can sometimes be debated.
Prescribing Errors: Illegible handwriting or incorrect entries in electronic health records can lead to mistakes by pharmacists or nurses.

Surgical and Procedural Complications

Surgical and procedural adverse events are often among the most serious.

Wrong-site, Wrong-procedure, or Wrong-patient Surgery: These are considered "never events"—highly preventable incidents that should never occur.
Retained Foreign Objects: Items like sponges or instruments are left inside a patient's body after surgery.
Post-Surgical Infections: Infections can arise at the incision site or elsewhere in the body following a procedure.
Complications from Anesthesia: Rare but serious adverse events can result from errors in the administration or management of anesthesia.

Healthcare-Associated Infections (HAIs)

HAIs, or nosocomial infections, are infections acquired by a patient during a hospital stay or while receiving care.

Central Line-Associated Bloodstream Infections (CLABSIs): Infections occurring from central venous catheters.
Catheter-Associated Urinary Tract Infections (CAUTIs): Infections related to urinary catheter use.
Surgical Site Infections (SSIs): Infections at or near the incision site after surgery.
Pneumonia: Infections of the lungs, especially common in patients on ventilators.

Diagnostic Errors

Failure to make an accurate or timely diagnosis can have profound consequences for a patient.

Delayed Diagnosis: Significant delays in diagnosing a condition can lead to progression of the disease and a worse prognosis.
Misdiagnosis: The incorrect identification of a patient's medical condition.
Failure to Act on Test Results: Overlooking or failing to follow up on abnormal lab results or imaging findings.

Patient Safety and Environmental Events

These events relate to the patient's immediate environment and overall care management.

Patient Falls: Particularly common in older adults or those with mobility issues, falls can result in serious injuries such as fractures or head trauma.
Pressure Ulcers: Also known as bedsores, these are injuries to the skin and underlying tissue resulting from prolonged pressure.
Incorrect Patient Identification: Misidentification can lead to a host of other errors, including wrong-patient surgery or mismatched blood transfusions.
Elopement: The unauthorized departure of a patient from a healthcare facility, particularly those who may be at risk.

The Importance of Reporting and Analysis

Reporting adverse events is a cornerstone of patient safety. Transparent reporting allows for the identification of systemic issues, rather than just individual errors. Root cause analysis (RCA) is a process used to identify the underlying causes of an adverse event, so that steps can be taken to prevent future occurrences. A culture of safety where healthcare providers can report events without fear of punishment fosters learning and continuous improvement.

Conclusion

Understanding what are examples of adverse events is the first step toward improving patient safety. From medication mix-ups to surgical mistakes, these incidents highlight the inherent risks in complex healthcare systems. By focusing on systemic improvements, reporting, and a culture of transparency, the healthcare community can continue to work toward the ultimate goal of zero patient harm.

For more information on patient safety, refer to resources from the Agency for Healthcare Research and Quality (AHRQ).

Frequently Asked Questions

An adverse event refers to any harm to a patient caused by medical intervention, while a medical error is an action or omission that has the potential to cause harm. An error does not always result in an adverse event, and an adverse event doesn't always stem from a preventable error.

Yes, a patient fall within a healthcare facility is a common example of an adverse event, especially if it results in injury.

A sentinel event is a specific, serious type of adverse event that is unexpected and involves death or serious physical or psychological injury. It signals the need for immediate investigation and response.

Prevention involves implementing robust safety protocols, improving communication among staff, leveraging technology to reduce human error, and fostering a culture of safety where reporting and learning are encouraged.

Healthcare providers and facilities are responsible for reporting adverse events to relevant regulatory bodies, which use the data to improve overall safety standards.

Yes, adverse events can occur in any healthcare setting, including outpatient clinics, long-term care facilities, and even during self-care.

Reporting adverse events is crucial for identifying patterns, root causes, and systemic issues. This information allows organizations to implement targeted corrective actions and improve patient safety for everyone.