Overdose prevention
Risk can rise with unknown strength, mixing, using alone and a drop in tolerance. Opioids mixed with alcohol, benzodiazepines or gabapentinoids are especially concerning.
Practical action
Harm reduction
Clear steps to reduce preventable harm — without judgement, false reassurance or requiring someone to be ready to stop using drugs.
TD ConsultancyPublished 5 August 2026Reviewed 5 August 2026NHS · OHID · UKHSA
When to call 999
Call 999 if someone is unconscious or cannot be woken, is not breathing normally, has a seizure, collapses, has severe chest pain, is dangerously overheated or is severely confused and at immediate risk. Tell the call handler what you know.
Suspected opioid overdose: call 999, give naloxone if available and follow the product instructions. Stay with the person.
Essentials
Six high-value actions
Naloxone
Naloxone can temporarily reverse opioid overdose. Call 999 as well: its effect can wear off before the opioid does and more than one dose may be needed according to the product instructions.
Changing tolerance
Tolerance can fall after a break, detoxification, hospital stay, prison release or a period of reduced use. Returning to a previously familiar amount can then be dangerous.
Unknown strength & contamination
Appearance, packaging and a familiar seller do not confirm contents or strength. Unexpected synthetic opioids and other adulterants can change risk.
Drug checking
Where a recognised checking service is available it can add useful information, but no result guarantees purity, dose, identity throughout a sample or safety.
Avoid using alone
For people at opioid-overdose risk, having someone able to respond and access naloxone can shorten the time to emergency action.
Situation guides
Risks change with the substance and setting
01
Opioids, nitazenes & heroin
Prioritise naloxone, avoiding depressant combinations, awareness of lowered tolerance and rapid response to slowed or abnormal breathing. Unexpected synthetic opioids can make strength especially uncertain.
02
Alcohol & benzodiazepines
Heavy sedation can become a medical emergency. Abrupt withdrawal after sustained heavy alcohol or benzodiazepine use can also be dangerous; seek clinical advice rather than attempting an unsupported sudden stop.
03
Stimulants
Multiple stimulants, long sessions, heat and sleep deprivation can increase cardiovascular strain, agitation and paranoia. Chest pain, seizure, collapse or dangerous overheating needs urgent assessment.
04
MDMA, heat & hydration
Hot environments and prolonged exertion can increase overheating risk. Both dehydration and excessive water intake can be dangerous. Severe heat, confusion, collapse or seizure is an emergency.
05
Synthetic cannabinoids
Products can vary substantially within and between batches. Severe agitation, confusion, chest pain, collapse or seizures warrant urgent medical help.
Safer smoking
Avoid sharing mouthpieces where possible; burns and damaged equipment can add harm. Smoke can irritate lungs regardless of substance.
Safer injecting
Use sterile equipment for every injection and do not share needles, syringes, spoons, filters or water. Local needle and syringe programmes can provide equipment and advice.
Infection & sexual health
Blood-borne virus testing, vaccination where indicated, wound care, contraception and sexual-health services can all sit alongside drug treatment or harm reduction.
Panic, paranoia & crisis
Reduce stimulation, move away from traffic, water or heights and stay calm. If someone is severely confused, violent through fear, suicidal or medically unwell, call 999.
Test doses: a limit, not a guarantee
Using less initially may reduce exposure to an unexpectedly strong product, but does not make a drug safe and cannot reliably detect uneven contamination.
After the immediate risk
Harm reduction and treatment are not competing choices. People can use naloxone, drug services, medical care and recovery support in whatever sequence fits their needs.
Explore treatment options →Evidence, review and limits
Specific risks depend on substance, strength, amount, route, tolerance, health, medicines and what else has been taken. This page provides education, not personalised medical clearance or dosing instructions.
Reviewed: 5 August 2026 · TD Training & Consultancy Ltd.
Professional depth
Lean (Purple Drank): A Practitioner’s Guide
For practitioners needing deeper context on codeine-based mixtures, opioids, sedating antihistamines and harm reduction.
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