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.

Overdoses are often accidental and can come on quickly and unexpectedly. Warning signs differ based on the type of substance used, but any sudden change in breathing, consciousness, or behavior should be taken seriously.

Below are common signs of overdose for central nervous system (CNS) depressants and stimulants. If you suspect an overdose, call 911 immediately.

Central nervous system depressants include opioids, benzodiazepines, and alcohol. These substances slow down brain activity, breathing, heart rate, and other essential functions. When too much is taken, these systems can slow to the point of stopping.(Source)

Common CNS depressants include:

• Prescription opioids (such as oxycodone, hydrocodone, morphine, fentanyl)
• Illicit opioids (such as heroin and non-prescribed fentanyl)
• Benzodiazepines (such as Xanax, Valium, Ativan, Klonopin)
• Alcohol

Mixing these substances together (for example, opioids with benzodiazepines or alcohol) greatly increases the risk of overdose and death.(Source)

Benzodiazepine overdose can occur when someone takes too much of the medication, uses it more often than prescribed, or combines it with other depressants like alcohol or opioids.(Source) The way the drug is taken (swallowed, injected, or snorted) and whether it is short-acting or long-acting can also affect overdose risk.

Possible signs of benzodiazepine overdose include:

• Difficulty breathing or not breathing
• Blue or gray lips or fingernails (cyanosis)
• Confusion, disorientation, or extreme dizziness
• Blurred or double vision
• Weakness or uncoordinated muscle movements
• Tremors
• Profoundly altered mental status (unresponsiveness, inability to wake up)
• Slurred speech
• Low blood pressure and slow heart rate
• Coma in severe cases

Benzodiazepine overdoses are especially dangerous when combined with opioids or alcohol, because all three slow breathing and can lead to respiratory arrest.(Source)

Opioid overdose has become increasingly common in the United States and remains a leading cause of injury-related death.(Source) Overdoses can occur with prescription opioids, heroin, or synthetic opioids like fentanyl.

Opioid overdose may happen when:

• A person takes more than prescribed or uses opioids in a way not directed by a doctor
• Someone returns to use after a period of abstinence (such as after detox, jail, or rehab) and uses the same amount they used before, even though their tolerance is lower
• Drugs are mixed with other depressants like alcohol or benzodiazepines
• Illicit drugs are contaminated or “cut” with potent synthetic opioids like fentanyl or nitazenes, often without the user’s knowledge(Source)

Common signs of opioid overdose include:

• Pinpoint (very small) pupils
• Loss of consciousness or inability to wake up
• Slow, shallow, or stopped breathing
• Gurgling, choking, or snoring-like sounds
• Pale, clammy, or bluish skin, lips, or fingernails
• Slow heart rate and low blood pressure
• Extreme drowsiness
• Nausea or vomiting

If you see these signs, treat it as an emergency and call 911 immediately.

Opioid overdose can often be reversed if naloxone (Narcan) is given quickly and emergency medical care is provided.(Source) Naloxone is a medication that rapidly blocks opioid receptors, reversing the effects of opioids on breathing and consciousness.

Key facts about naloxone:

• It works only on opioid overdoses and is not effective for overdoses from stimulants or alcohol alone.
• It can be given as a nasal spray or injection.
• It begins working within minutes but may wear off in 30–90 minutes, while some opioids remain in the body longer.(Source)
• Multiple doses may be needed for strong opioids like fentanyl.

In many states, naloxone is available without an individual prescription at pharmacies, and it is often distributed for free or at low cost through community programs, harm reduction organizations, and public health departments.(Source)

Anyone who uses opioids, takes high-dose opioid prescriptions, or has friends or family who use opioids should consider carrying naloxone. It is safe to use even if you are not sure whether the person is experiencing an opioid overdose, and it can save lives.(Source)

Even if naloxone seems to reverse the overdose, it is vital to call 911 and seek medical attention. The person can stop breathing again after the naloxone wears off, especially with long-acting or high-potency opioids.

Alcohol overdose, also called alcohol poisoning, happens when there is so much alcohol in the bloodstream that basic life-support functions—such as breathing, heart rate, and body temperature—begin to shut down.(Source)

Alcohol overdose is common with binge drinking, which is typically defined as consuming enough alcohol to bring blood alcohol concentration (BAC) to 0.08% or higher, often 4 or more drinks for women or 5 or more drinks for men within about 2 hours.(Source)

Symptoms of alcohol overdose may include:

• Difficulty breathing or not breathing
• Slow or irregular breathing (fewer than 8 breaths per minute or pauses of 10 seconds or more)
• Confusion, stupor, or inability to stay awake
• Vomiting, sometimes repeatedly
• Seizures
• Pale, bluish, or cold skin
• Very low body temperature (hypothermia)
• Unresponsiveness or unconsciousness
• Risk of choking on vomit

If someone is showing these signs, do not leave them alone, do not try to “sleep it off,” and do not give them coffee, cold showers, or more food or fluids. These common myths do not reverse alcohol poisoning and can be dangerous.(Source) Call 911 immediately.

Stimulants such as methamphetamine and cocaine affect the central nervous system by increasing activity in the brain and body. They raise heart rate, blood pressure, and body temperature, and can cause the heart and blood vessels to work far beyond safe limits.(Source)

A stimulant overdose occurs when these effects become so intense that the body can no longer cope, leading to heart attack, stroke, seizures, or organ failure.

Common stimulants include:

• Methamphetamine (meth, crystal meth)
• Cocaine and crack cocaine
• Prescription stimulants (such as Adderall, Ritalin, Vyvanse) when misused

Mixing stimulants with other drugs, including alcohol or opioids, can increase the risk of overdose and complicate treatment.

Methamphetamine can be snorted, injected, swallowed, or smoked. Using large amounts, using repeatedly over a short period, or combining meth with other substances can lead to overdose.(Source)

Symptoms of methamphetamine overdose may include:

• Enlarged (dilated) pupils
• Chest pain or tightness
• Irregular heart rate (very fast, very slow, or skipping beats)
• Difficulty breathing or shortness of breath
• Very high blood pressure
• Very high body temperature (hyperthermia), often with sweating or hot, flushed skin
• Heart attack
• Stroke
• Kidney failure
• Severe stomach pain or cramping
• Extreme agitation, restlessness, or panic
• Paranoia, hallucinations, or psychotic episodes
• Violent or unpredictable behavior
• Suicidal thoughts or behavior
• Seizures
• Loss of consciousness or coma

Stimulant overdoses can progress quickly. If you notice these signs, call 911 immediately and stay with the person until help arrives.

Overdoses can cause serious, permanent health complications or death if not treated as soon as possible. If you suspect someone may be overdosing, it is always safer to act quickly and call for help.

Steps to take if you think someone is overdosing:

1. Call 911 immediately.

• Describe the person’s symptoms and, if possible, what substances they may have taken and when.
• Follow the dispatcher’s instructions carefully.

2. Check for breathing and responsiveness.

• Try to wake the person by calling their name and gently shaking them.
• If they are not breathing or are breathing very slowly or irregularly, tell the 911 operator.

3. Use naloxone if you suspect an opioid overdose.

• If you have naloxone (Narcan) and suspect opioids are involved, give it right away.
• Follow the instructions on the package for nasal spray or injection.
• If there is no response in 2–3 minutes and emergency services have not yet arrived, a second dose may be needed.(Source)

4. Place the person in the recovery position if they are breathing but unconscious.

• Gently roll them onto their side.
• Bend the top leg and place the hand under the head to keep the airway open.
• This position helps prevent choking if they vomit.(Source)

5. Do not give food, drink, or other substances.

• Do not give coffee, cold showers, or other “home remedies”—these do not reverse overdose and can make things worse.
• Do not try to make the person vomit.

6. Stay with the person until help arrives.

• Monitor their breathing and level of consciousness.
• Be prepared to perform CPR if instructed by the 911 operator and you are able.

If the individual has overdosed on alcohol, do not place them in a cold shower or give them coffee. These treatments are myths and do not help the individual recover from an overdose. Call 911 for help immediately and stay with them until they arrive.(Source)

Many people hesitate to call for help during an overdose because they fear arrest or legal trouble related to drug or alcohol possession. To address this, most U.S. states and the District of Columbia have enacted some form of “Good Samaritan” or overdose immunity law that offers limited legal protections to people who seek medical help during a suspected overdose.(Source)

These laws vary by state but often provide some protection from arrest or prosecution for:

• Possession of small amounts of drugs or drug paraphernalia
• Underage drinking or alcohol possession

The goal of these laws is to encourage people to call 911 without delay when someone’s life is at risk.

Because Good Samaritan protections differ by location and can change over time, it is important to check your state’s current law or speak with a legal professional for specific information.(Source) Regardless of the law, medical emergencies should always take priority—calling 911 can save a life.

An overdose can occur the first time someone uses a substance or after many years of use—it depends on the person’s health, tolerance, the substance, and how it was taken.(Source) However, repeated or escalating substance use significantly increases the risk of overdose, especially when multiple substances are combined.

If an overdose occurs in the context of ongoing drug or alcohol use, it is often a sign that professional help is urgently needed. Addiction is a chronic medical condition that affects the brain and behavior, making it difficult to stop using substances even when they cause harm.(Source)

Treatment and support can help people:

• Safely withdraw from substances under medical supervision
• Learn coping skills to manage cravings and triggers
• Address underlying mental health conditions such as anxiety, depression, or trauma
• Rebuild relationships, work, and daily functioning

Evidence-based treatment options may include:

• Medical detox to manage withdrawal safely
• Residential or inpatient treatment for structured, 24/7 support
• Outpatient programs that allow people to live at home while receiving care
• Medication-assisted treatment (MAT) for opioid or alcohol use disorders, using medications such as buprenorphine, methadone, or naltrexone alongside counseling(Source)
• Individual, group, and family therapy
• Aftercare and relapse prevention planning

If you or someone you love has experienced an overdose or is at risk, reaching out for help can be a turning point. Recovery is possible with the right support, and you do not have to face it alone.