In the United States, almost 110,000 people died from drug overdoses in 2022, apparently driven largely by fentanyl.

I don't know the biology of it, but it occurs to me that surely something helpful could be said about safe dosing for illegal drugs (i.e., more than just “these drugs are harmful in any quantity”).

I'm curious whether any governments have published these sorts of guidelines. It seems to be equivalent to programs that provide needles or safe spaces for drug users to inject.

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    Medical studies release lethality reports on a lot of substances (and not only illegal drugs); typically refered as LD. For example LD50 means a dosis that has a 50% chance of killing you. But that is the ballpark of science, not of governments.
    – SJuan76
    Sep 23, 2023 at 11:34
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    And this question seems to imply that illegalization to drugs is only because of OD. But a "safe" dosis can have negative effects: people become addicted, people start taking more and more (up to the time it is not safe anymore). Even "safe" drugs from which an OD is rarely lethal (weed) can have social and individual social effects that can induce people to ban them. And sometimes governments and other organizations even try to provide incentives for people to leave drugs that are legal and "safe", due to their health effects (alcohol, tobacco).
    – SJuan76
    Sep 23, 2023 at 11:38
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    @SJuan76 Well, that implication wasn't intended, anyway (that legalization is associated with OD risk). I wouldn't want to pursue that line of argument, because it's easy to OD on acetaminophen, and I don't want that to be banned!
    – adam.baker
    Sep 23, 2023 at 15:58
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    people do not overdose because they take 3 pills of something standardized and well labelled that would have been ok if they took 2. They overdose because they think it's something they can take 10 of (making 2 fine) but it's actually something where 1 will kill you. And that's because someone didn't stir or filter or whatever something quite properly. So telling people the safe doses would change nothing unless there was also a safe and regulated supply. That's what's causing overdoses, not a lack of guidelines on how much a safe dose would be. Sep 23, 2023 at 23:56
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    Or to put it in other words, governments might be able to give safe doses in mg of active ingredients, but if you don't know how many mq of the active substance are in the pill your seeing because it is from a completely untrusted supply chain with minimal to no QA and zero documentation? That information is completely useless to you. Sep 24, 2023 at 12:44

8 Answers 8


Offering generic advice of the form up to xxx mg are generally a safe dosage is very hard to give for illegal drugs because one doesn't know the exact quantities of the various ingredients. It is also common especially for hard drugs like that they are diluted by other substances that might be harmful themselves.

There is a related offer that is used, which is anonymous drug checking, see for example here for a relevant law in Germany. There are labs offering that in Berlin (source in German). What is done there is that you can get the specific drug you have tested and they will tell you whether the specific drug you handed them contains any substances it shouldn't contain and what a reasonable dosage might be.

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    Another factor is user-dependent. Simply put, how a frequent, habituated, opiate user will react to fentanyl will be very different from a "naive", non opiate using person encountering it unexpectedly in say what they thought was cocaine. The first may enjoy "a good hit". The second may very well have a lethal overdose. Source: my partner works in this field. Sep 23, 2023 at 15:48
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    When it comes to illicit drugs, there's little or no quality control happening at the manufacturing stage. A 'joint' harvested from two neighbouring plants grown at the same time from the same patch may have as much as 200mg of THC or as little as 0mg depending on the growing conditions.
    – Valorum
    Sep 23, 2023 at 17:22
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    With regards to the exact quantities of the various ingredients - it's worth noting that usually with regards to fentanyl specifically (Since it was mentioned in the question), it's not a main ingredient, but a smaller ingredient mixed into other stuff. That combined with the fact that illegal drugs almost certainly don't disclose their ingredients like most food products will list high-fructose corn syrup, meaning you can take something that seems safer (As opposed to the heroin example mentioned in my link), and still be getting fentanyl unknowingly. Sep 23, 2023 at 18:58
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    @ItalianPhilosophers4Monica Seconded--same thing happens with medical use. The doctors have to keep track so the patient that goes into the hospital gets handled correctly. What's lethal to a naive patient won't provide much relief to the patient already on a high dose. Sep 24, 2023 at 2:31
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    @Valorum And this is a big reason to simply legalize drugs. Sep 26, 2023 at 2:02

Portugal would be one example, since drugs in Portugal were decriminalized a few years back. This means drug users there are treated as patients, not criminals and people are actually educated about effects and risks without being patronized by statements like "all drugs are always bad in all quantities, just never take them", which let's be honest, is not really constructive. When you're deliberately taking substances, you've already passed the point where these kind of generic warnings will stop you.

While not exactly related to the Fentanyl example that is adressed by the question, I was amazed being on a festival in Portgual once where there was not only a drug checking station, but also professionals to councel you or aid in an emergency. They also handed out actually informative flyers about which substances pose danger when mixed together, safe doses, what to look out for safe usage, how to act when something goes wrong, etc. so basically information that will - in my personal perception - more likely be taken seriously and therefore lead to less fatalities.

If this initiative had an actually measureable effect has no straighforward answer though, if you're interested in that, take a look at the different surveys and the research mentioned in the Wikipedia article https://en.wikipedia.org/wiki/Drug_policy_of_Portugal



Here, for example, is dosage guidance for cocaine in the US.

You might notice that this is for prescription purposes, and that's correct. The overwhelming majority of drugs are "illegal" in the US when used not in accordance with a prescription, and prescriptions generally guided by FDA-approved guidelines.

I haven't bothered to look, because I'm certain dosage guidelines exist for drugs which were later pulled from the market (i.e. which are now illegal).

So: yes. In general, there exist dosage guidelines for illegal drugs.

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    Well put, and I see that you're correct. I guess I should have specified “recreational doses.” :-)
    – adam.baker
    Sep 26, 2023 at 5:08

Frame challenge: almost no one actually is looking for fentanyl, they overdose because another drug was cut with fentanyl and the difference between a "safe" amount and a lethal dose is extremely small. And providing a "safe" dose amount wouldn't matter anyway because it's not like you get a lab report when you buy illegal drugs.

That being said, is very easy to find these numbers for almost any drug, but again it's irrelevant to the real world recreational use unless you are dealing with pharma grade medication.


“these drugs are harmful in any quantity”

When it comes to something that might have been cut with fentanyl, this is the only thing that can really be said. You are talking about a drug where 0.1 mg is a therapeutic level dose, 0.5 mg is a large recreational dose, and 1mg is probably fatal. These are differences that are in the level of specks of dust.

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    Sorry, factually incorrect. Plenty of hardcode opiate users do look specifically for fentanyl. It's cheap and gets you very high. Now, it is true that many die of taking it inadvertently, but those are not the same users and the presence of a second population does not do away with the existence of the first. To the point where we have pilot program to provide f. going bccsu.ca/blog/news/… Sep 24, 2023 at 16:29
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    Exactly this. OP's question is utterly absurd imho, because it implies that people are dying because they're just taking too much out of ignorance.
    – Hobbamok
    Sep 25, 2023 at 12:23
  • One of the big factors for fentanyl ODs because it is so potent is that when you cut it with something else (e.g. to substitute for a less potent per gram opiate) if the mixing isn't laboratory grade perfect, some doses will be a bit high and some doses will be a bit low from the average, and the doses with an overdensity of fentanyl are deadly. Of course, in a black market, perfect laboratory grade mixing is often not achieved. Fentanyl is encouraged by the black market, however, because the higher the dose/gram, the more $$ per gram and the easier it is to smuggle.
    – ohwilleke
    Sep 27, 2023 at 20:30

For Fentanyl specifically, it's impossible to provide meaningful guidance.

It's so potent and is lethal in such small doses(~2mg), that you need lab-grade equipment to dose correctly, while the stuff that gets into the street is cut into other drugs by your neighborhood high-school dropout dealer using a kitchen scale for measurement, so 2 batches can easily differ in potency by 2 orders of magnitude.

  • Yep, the implication of OPs question: That people OD simply because they didn't have dosage information is ridiculous to the point of being insulting
    – Hobbamok
    Sep 26, 2023 at 8:14
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    @Hobbamok Those high school dropout dealers may very well have the dosage information. What they don't have is the equipment and lab skills to blend it and dose to the desired amount correctly.
    – ohwilleke
    Sep 27, 2023 at 20:32
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    @ohwilleke that was ma point: good dosage information is very very easy to obtain. Getting your hands on street drugs pure enough for that information to be applicable isn't.
    – Hobbamok
    Sep 28, 2023 at 10:05

Why would they?

Reliable dosing information is already widely available to anyone caring to look

Governments, especially the American one have a really bad track record when it comes to honest treatment of drug users, so I'd expect little to no confidence in official figures. Secondly, unofficial resources can go far further into detail (regarding the complexities of street-sourced compounds) than I imagine any government would care to (or want to given the shady association).

So not only would they be competing with known-and-trusted sources, they'd also risk their image by associating with drug use, risk looking like drug use is officially condoned (something that could end a politicians career), and potentially risk liability if someone does overdose while relying on their (now very official) information.

And that last part is crucial: (lack of) Dosage information isn't what kills people by overdose. But if the government says that X mg of Opiate Y is fine for someone, and they die because they (unknowingly) have stronger Opiate Z, relatives may see the government liable (regardless of the legalistic outcome of a case, the sentiment of responsibility will remain).

These risks with practically 0 benefit are simply not worth it.


The OP asks about dosing guidelines, but a policy with a similar outcome would be to have people use narcan. The health department of New York City has recently recommended that all of its citizens do just this.

  1. All New Yorkers should learn the signs of an overdose and, in the event they encounter such an emergency, call 911 immediately and administer naloxone if they have the medication on hand.
  2. All New Yorkers should be equipped with and trained in naloxone administration.

Given the lack of quality control in the illicit drugs market—described in many of the other answers—this would surely be the better way to tackle the overdose problem.


Why would they?

For a government to publish statements that might be interpreted as "here's how to use the things we are always telling you not to use", is a bad look for authoritative leadership who supposedly know what's best for everyone. They'd be tying their own noose with that paradox.

Plus, what do they know anyway? That's not just me having a cocky attitude - I mean it literally. Are "they" actually knowledgeable about the recreational use of these substances? The lawmakers generally seem pretty ignorant when it comes to both personal experience and doing their own research. That is why (to give an example) psilocybin mushrooms which grow naturally on the earth, and are not poisonous to humans, get classified as "schedule 1 drugs" - meanwhile the tobacco industry (an example on the opposite extreme) lobbies and makes deals with influential people in government so it can be allowed to carry on doing business as usual, even though it's common knowledge that smoking is addictive and harmful to health.

You can think of it this way: It's okay for some substances to kill you, but not okay for other substances to kill you. It's also not okay for some substances to not kill you (psilocybin, LSD, etc won't). Which substances get placed in which category is a matter that will be determined by people who have likely never ingested them and are only vaguely or anecdotally familiar with their physiological or psychological effects.

On the flip side, there are also plenty of very harmful and addictive illicit drugs in existence. So there are often legitimate reasons to regulate and take precautions. Unfortunately, once policy is written into law, it becomes difficult to change, even decades later when the public's awareness has increased, scientific knowledge has improved, and there is a better understanding of what is and isn't dangerous - and how much risk a given substance actually poses to the public.

Decisions by governments about "drugs" is anything but nuanced. And they are risk-averse.

I get what you mean though. Having a resource people can look to in order to try to stay safe seems like a great idea. But governments are unwilling or unqualified to navigate that space and all its complexities. The populous at large are also guilty of lazily looking to their governments to have all the answers instead of studying up on matters from their own initiative.

In summary, governments are not going to provide guidance on recreational substance use. However, there are educational resources such as Erowid that document the experiences others have had. In their own words, they are "Documenting the complex relationship between humans and psychoactives". And it is a complex relationship, varying greatly depending on the substance, the dosage, the individual, and even when/where/how often/with whom else - numerous circumstantial variables.

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    Why do you think that the lawmakers would be the ones determining what the limit is? They would be calling on experts to do that work for them and those experts would be publishing the results.
    – Joe W
    Sep 24, 2023 at 3:36
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    This doesn't answer the question but is just your personal opinion on the topic and politics.
    – quarague
    Sep 24, 2023 at 5:23
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    More right than wrong here. Drug policy has long been more about politics and culture, more so than strictly medical aspects. The notion that experts are trusted to decide is quaint, naive and not warranted by actual policy. Look at cannabis scheduling in the UK. Or, look to the very brief career of one Dr. Schwartzenberg, a one-week French Health Minister. A doctor, his mistake was to state that cannabis could be considered less problematic, health-wise, than alcohol. Look at US criminal penalties for cocaine vs crack. Sep 24, 2023 at 21:05
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    Why would they? Quite easy: "We don't want you to do this, but if you ignore our laws we'd rather you not die, so please adhere to these guidlines". Sep 25, 2023 at 5:21
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    I downvoted this answer because "Why would they?" has an obvious answer ─ harm reduction ─ and the rest is an argument based on the idea that all governments are too blinkered to adopt harm reduction policies, but that is objectively not true. The question is "have any governments" done this, the correct answer is "yes" (see other answers about Germany and Portugal), so it's not useful to have an answer explaining why the answer might hypothetically be "no".
    – kaya3
    Sep 25, 2023 at 18:17

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