An opioid overdose can happen for many different reasons. Some of the most common causes include:

Individual
- When a patient misuses a prescription on purpose.
- When someone uses an illegal drug like heroin.
- When someone uses an opioid contaminated with an even stronger one like fentanyl.
- When a patient using prescription opioids misunderstands the directions for use.
- When someone mixes opioids with other kinds of medication.

Physician
- When the person prescribing an opioid miscalculates the dosage amount.

Pharmacist
- When the pharmacist providing medication makes a mistake.
