What is it?
Heroin is an opioid. Street supply varies in strength and may be adulterated, including with other potent opioids, which makes strength unpredictable.
Common forms
- Powder
- Prepared solutions for injection
- Smoked ('chasing')
How it affects the body
Opioids act on opioid receptors, reducing pain and producing sedation. They also slow breathing, which is what makes opioid overdose life-threatening.
Short-term effects
- Pain relief and sedation
- Warmth and detachment
- Nausea and vomiting
- Slowed breathing
- Small pupils
Long-term effects
- Dependence and tolerance
- Constipation and dental problems
- Injecting-related injuries and infections
- Blood-borne viruses where equipment is shared
- Significant social and financial harm
Dependence and addiction
Dependence can develop when the body and brain adapt to regular use. It is not a moral failing or a lack of willpower. Signs people describe include needing more to get the same effect, difficulty cutting down, spending more time thinking about use, and continuing despite harm. Support is available at any stage — you do not need to have reached a crisis point. Opioid dependence is treatable, and opioid substitution treatment is an established part of UK care.
Withdrawal
Stopping or reducing after regular use can cause withdrawal. Withdrawal varies between people and depends on how much and how long someone has used, their physical health and other substances involved. Some withdrawal can be medically serious, so it is safer to plan a reduction with a clinician or a drug and alcohol service rather than stopping abruptly alone. Opioid withdrawal is intensely uncomfortable and can be dangerous when someone is unwell, pregnant or dehydrated. Importantly, tolerance falls quickly during any break in use — including after prison, hospital or detox — which raises overdose risk if use restarts.
Overdose risks
Signs include unresponsiveness, very slow or stopped breathing, snoring or gurgling sounds, blue or grey lips and pinpoint pupils. Call 999, use naloxone if you have it, and put the person in the recovery position. Naloxone temporarily reverses opioid overdose — always call an ambulance as well.
Mixing substances
Mixing opioids with alcohol, benzodiazepines, gabapentinoids or other sedatives sharply increases the risk of stopped breathing. Most opioid deaths involve more than one substance.
Harm-reduction information
- Carry naloxone and make sure people around you know how to use it
- Avoid using alone, or make sure someone can check on you
- Never share injecting equipment
- Take extra care after any break in use — tolerance drops
- Contact a local service for naloxone, testing and treatment options
When to seek urgent medical help
Call 999 if someone is unconscious or cannot be woken, is having difficulty breathing, has a seizure, has chest pain, becomes very confused or agitated, or you are worried they may have overdosed. For urgent advice that is not life-threatening, call NHS 111. You will not get someone into trouble by calling for medical help.
Treatment and recovery options
- Talking therapies and structured psychosocial support
- Community drug and alcohol services, including self-referral where available
- Medication-assisted treatment where clinically appropriate
- Medically supported withdrawal, arranged and monitored by clinicians
- Peer support and recovery communities
- Residential rehabilitation for some people, usually via assessment
- Support for related needs — mental health, housing, family and welfare
UK support resources
- NHS — health information and service finders (nhs.uk)
- Talk to FRANK — UK drug information service (talktofrank.com)
- Your local community drug and alcohol service — many accept self-referrals
- Local pharmacy teams, who can offer advice and signposting
Sources / references
This page is a plain-language summary written for education. For clinical or legal detail, use authoritative UK sources: NHS (nhs.uk), Talk to FRANK (talktofrank.com), NICE (nice.org.uk), UK Government and devolved government publications, and guidance from UK professional bodies. Each page on this site carries a review date, and we welcome corrections.