An overdose occurs when a person knowingly or unknowingly takes too much of a substance, such as prescription medications, illicit drugs, or alcohol, and the body cannot process the amount taken.(Source) This overwhelms vital systems like breathing, heart function, and brain activity.

During an overdose, the brain may not receive enough oxygen, which can cause long-term brain injury even if the person survives.(Source) This lack of oxygen (hypoxia) can impair memory, thinking, movement, and emotional regulation.

Some possible neurological symptoms after an overdose can include:

• Short-term memory loss
• Disorientation or confusion
• Acute amnesia (sudden, significant memory loss)
• Difficulty concentrating or processing information
• Changes in mood, behavior, or personality

Physical problems after an overdose may include:

• Loss of control over bodily functions
• Lack of coordination or balance
• Nerve damage
• Reduced motor function, such as weakness or loss of use of a limb
• Paralysis in severe cases
• Overall diminished physical functioning and stamina

Overdoses can happen at any time, including the first time someone uses a substance or after years of use. Tolerance, health conditions, mixing substances, and changes in drug supply (such as fentanyl contamination) all affect overdose risk.(Source) Regardless of the cause, every suspected overdose is a medical emergency.