All drug use has risks. This page is for information only and does not constitute or replace medical advice. If you have medical concerns about your drug use, please speak to a medical professional.
Synthetic Cannabinoids

Fentanyl is a highly potent synthetic (lab-made) opioid. It has been used as an analgesic (pain-killing) medicine since the 1960s.

Recently fentanyl use has emerged in non-medicinal drug markets, either sold as fentanyl or more commonly found as an adulterant (unexpected ingredient) in other drugs. In many countries, fentanyl has been detected as products mis-sold as heroin, benzodiazepines (such as diazepam and etizolam), cocaine and gabapentinoids.

It is active in lower doses than heroin so a much smaller dose is needed to feel the effects. Anyone who takes drugs should be aware of the risks of adulterants, test the drugs, start with a test dose and use fentanyl test strips.

Other names



Fine white, gray or tan powder

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Misuse of Drugs Act (1971) – Class A.

If not prescribed/medically administered, fentanyl (and most of its analogues) are Class A drugs.

Penalties for possession are up to 7 years in prison and/or an unlimited fine. Penalties for supply are up to life in prison and/or an unlimited fine.


The following information on dosage was taken from PsychonautWiki, but this should not be taken as a recommendation: duration and effects of any drug will depend on purity, regularity of use, other medications or drugs you have taken, your body and how it is taken (route of administration).  

Insufflate (snort): 

  • Light: 10-25 micrograms (μg) 
  • Common: 25–50 micrograms (μg) 

Accessed November 2020  

It is essential to use accurate scales – ones that are capable of measuring to 10 micrograms (0.00001 of a gram). Knowledge of how to use them and how to ensure they are measuring accurately is important.  

A slight difference in dose can create a different experience or effect. Find out more about reducing the risk from dosing including volumetric dosing.

General information on dosing.


Fentanyl is a painkiller that can cause sedation and drowsiness. People may feel warm, safe and relaxed. It can also cause constipation, nausea and vomiting. Some of the effects are similar to other opioids, such as heroin, but people generally report experiencing less euphoria (feelings of happiness) with fentanyl.

Fentanyl can cause respiratory depression (slowed/shallow breathing and reduced heart rate) and death.

There are many other types of synthetic opioid that have similar effects. These include drugs such as fentanyl analogues like acetyl, butyl, or furanyl-fentanyl, and as well as opioid-type new psychoactive substances (NPS), such as U-47700. Research is limited for many of these drugs and great care and caution is advised.


The use of fentanyl comes with extreme risk. If you are determine to take it, be aware that:

  • Fentanyl is active in lower doses than heroin so a much smaller dose is needed to feel the effects. Fentanyl is often described as being 50 times stronger than heroin, so 50 times less is needed to get the intended effect. Take care when dosing – even a small difference in dose can make the difference between feeling the intended effects and overdose.
  • The fentanyl can be spread unevenly throughout a bag of powder or batch of pills. This means some pills/powder contains no psychoactive substance whereas other pills/parts, contain much more than expected. If taking powder, mix the product well before testing and use.
  • If taken frequently, a tolerance to fentanyl will develop. Tolerance to a drug means that a higher dose of the drug is needed to achieve the desired effect, which increases the risk of overdose and dependency.
  • Physical dependence to opiates can happen quickly, after only a few days of use. This means people will experience withdrawal symptoms if they do not take the drug. Limit use, and take regular breaks from use to allow your body time to heal and readjust.

Harm reduction

If you choose to take fentanyl then the following steps can help to reduce harm.

General harm reduction

  • If you can, get your drugs tested. Without testing your drugs there is no way to be sure that they contain only or any of the drugs you think you have. Visit WEDINOS.
  • In many countries, fentanyl has been found in products sold as heroin, benzodiazepines (such as diazepam and etizolam), cocaine and gabapentinoids. Fentanyl test strips can confirm the presence of fentanyl in products – these are available to order online.
  • Start low, go slow! Start with a small test dose to feel the effects.
  • Avoid taking drugs alone but if you do, let someone who can check on you know what you are taking, how much and when.
  • Avoid mixing drugs, including alcohol and medicines.
  • Avoid sharing equipment including needles, cookers, snorters or pipes etc.

Fentanyl harm reduction

  • Start with a test dose – smaller than a matchstick head size and wait a few hours before taking more.
  • If you are injecting avoid ‘slamming’ the hit quickly and instead slowly press the needle so that you can manage your dose better.
  • Injecting is the most risky way to take fentanyl – when you have a new batch try smoking or snorting your test dose of it instead of injecting.
  • Snorting or smoking is less risky than injecting but there is still a risk of overdose.
  • Mixing fentanyl with other downers (including heroin, alcohol and benzodiazepines) is extremely dangerous and increases the risk of respiratory depression and death.
  • Always carry naloxone, this can be used to temporarily reverse an opioid overdose. You may need to use more than one dose of naloxone. The naloxone may also take longer to work than it would with other opioids – wait 2-3 minutes and give another dose.
  • If you are taking drugs in a group ensure multiple naloxone kits are available and that one person is alert/sober enough to respond to an emergency (space out your dosing, instead of everyone dosing at the same time).
  • Those in Scotland can order a naloxone kit from Scottish Families Affected by Alcohol and Drugs.
  • Sleep on your side. This will help to keep your airway clear.
  • Call 999 and ask for an ambulance if you see the signs of an overdose: confusion, unconsciousness (won’t wake with a shout or a shake), severe nausea and vomiting, fitting, difficulty breathing, snoring/raspy breathing, blue/pale tingeing of knees, hands and lips, slow or erratic pulse (heartbeat), pale, cold and clammy skin, seizure-like symptoms (fits/muscle spasm/rigid or tight muscles/tightness in the chest that makes breathing difficult).