A heroin overdose can quickly become life-threatening. Learn the warning signs, why overdose happens, and what to do if someone may be in danger.
A heroin overdose occurs when the drug suppresses the body’s breathing to a dangerous level. Because heroin slows the central nervous system, taking too much can prevent the body from getting enough oxygen.
Overdose can happen suddenly and may become life-threatening without immediate help, so understanding the warning signs and knowing how to respond can make a critical difference.
If you’re concerned about heroin use more generally, you can read more about the wider risks and patterns of heroin addiction.
Why Heroin Overdose Happens
Heroin is an opioid drug that slows down breathing, heart rate and brain activity. When too much heroin is taken, the body’s ability to breathe normally can become severely reduced.
In some cases, breathing may slow to the point where oxygen can’t reach vital organs such as the brain.
Overdose risk can increase when:
- A larger amount of heroin is taken than usual
- Heroin is used after a period of abstinence, when tolerance has dropped
- Heroin is mixed with other substances such as alcohol, benzodiazepines, or certain medications
- The purity or strength of the drug is unknown.
Because illegal drugs are unpredictable, it’s often difficult for people to know exactly how strong a particular dose may be.
Signs of a Heroin Overdose
Recognising the signs of an overdose is extremely important. An overdose can progress quickly and may require urgent medical attention.
Common warning signs may include:
- Very slow, shallow, or stopped breathing
- Unconsciousness or the inability to wake the person
- Blue or grey lips and fingertips
- Pale or clammy skin
- Gurgling or choking sounds
- Extremely small pupils.
If someone shows these symptoms after using heroin, it may indicate an overdose.
What To Do If Someone Overdoses
If you believe someone is experiencing a heroin overdose, it’s important to act quickly.
In the UK, you should call 999 immediately and ask for an ambulance.
While waiting for help to arrive:
- Try to keep the person awake and responsive if possible
- Place them in the recovery position if they are unconscious but breathing
- Stay with them until medical help arrives.
Emergency responders are trained to manage overdoses and provide life-saving treatment when necessary.
Overdose Risk After Stopping Heroin
One of the most dangerous periods for overdose can happen after someone has stopped using heroin for a period of time.
When tolerance decreases, the body becomes more sensitive to the drug. If someone returns to heroin and takes a similar amount to what they previously used, the body may no longer be able to tolerate that dose.
This is one reason overdose risk can increase following a relapse.
The Link Between Withdrawal and Overdose Risk
People who stop using heroin may experience withdrawal symptoms as the body adjusts to the absence of the drug.
These symptoms can be physically and emotionally difficult, which sometimes leads people to return to heroin use to relieve the discomfort.
You can learn more about how this process works on our heroin withdrawal page.
Getting Help for Heroin Use
Heroin use carries serious risks, including overdose. For many people, recognising these risks is what leads them to begin looking for support.
Recovery often begins with stabilising physical health and addressing the immediate effects of heroin use. Some people start this process with a structured detox, which focuses on helping the body adjust safely after stopping heroin.
Longer-term recovery usually involves therapeutic support and learning new ways to manage the challenges that may have contributed to drug use in the first place. Our guide to addiction treatment explains how these stages of recovery typically work together.
