# The lethal dose of Cannabis?

Discussion in 'Medical Marijuana Usage and Applications' started by HeaDiEs RusH, Oct 31, 2011.

1. So, I know we've all heard the "you have to smoke 3x your own body weight in 30 min" or whatever it is that people always say, but what is the actual dose?

I have the Merck index 11th edition right in front of me and it says that the LD50 of THC ingested orally in sesame seed oil is 1270 mg/kg for male rats and 730 mg/kg for female rats. I did some calculations to try and figure out how many grams of cannabis plant that converts to, but I came up with a rather low number.

I assumed that there are 200 mg of THC per 1 gram of cannabis. I multiplied 1270 mg of THC per 1 kg of body weight by 1 gram of cannabis per 200 mg of THC to get 6.35 grams of cannabis per 1 kg of body weight. I then multiplied by 70 kg (assuming the average person weighs 70 kg) and got an answer of 444.5 grams of cannabis.

444.5 grams of cannabis is not 3x anyone's body weight. What gives? Am I missing something in my calculations?

2. That's still an absolute fuck ton. You'd pass out way before that.

3. I would think it takes more than that...

4. 200 mg of thc per gram is 20% thats high grade weed. I would assume those numbers were found using not so potent bud lol and thats why they are much higher

5. Those numbers were found using a THC extract (oil), so the quality of the plant they used wouldn't matter.

6. #6
Last edited by a moderator: Oct 31, 2011
I think it's more of an example than a real ratio. If the LD50 of THC were 3 X your body weight then it would be three kg's per kg. Mg's are parts per million

7. Lol this is true... didnt even consider that...

Maybe its factoring in the fact you wont absorb 200mg of THC from a gram containing 200mg.... so you need to consume more bud, than actually contains the LD50, to achieve it inside the body.... Or if eaten, maybe they are still assuming some of that THC passes through and is negated so the numbers end up higher?????

You know????

Ive got no clue

8. It is not physically possible to smoke enough weed to kill you. Not unless you build a new machine that can hold like pounds and pounds of weed and then light it with a fucking flame thrower. No normal method of weed consumption, edibles included, will kill you unless you have an allergy.

9. THC ingested orally in sesame oil is Marinol, not cannabis. I don't think Merck would list the LD50 of cannabis.

Yes Marinol has an LD50 that is feasible to ingest. Not true of cannabis.

10. mg is definitely not parts per million. ppm is parts per million. And yea the 3x your own body weight is just a general estimate, but 444 grams for a 70kg person is not even slightly consistent with that claim.

While I realize that smoking 444 grams of weed in half an hour would be pretty damn difficult and is pretty much all the evidence I need to say that you can't overdose of cannabis, I'm still just wondering where the "3x your own body weight" claim came from.

11. I always heard it as 3x your body weight, in smoke... not cannabis.... though i never regarded it as anywhere near the truth, but thats how i "heard it" hahahahaahha

Either way, the number seems kinda ridiculous....

12. The book appears to be referring the LD50 to delta 1 - THC, delta 9 - THC, QCD 84924, dronabinal, and Marinol. At least that's how I understand it.

13. I understand the confusion but this calls for mg per kg. That means 0.001 / 1,000 = 1/1,000,000 = one part per million. By that standard the 445 gram something LD50 makes sense for a 70 kg individual.

I believe the 3 X quote comes from word of mouth. By that point it becomes belief. Or it's just an example to show you it's impossible.

14. Oh ok yea I see what you were saying now. Damn though, I really was hoping for a larger number than that. Oh well.

15. You may find the second link interesting;

First; From here; Thc Ld-50? - Marijuana.com

the MSDS [Material safety data sheet] on Delta-9 THC gives the LD-50 as:

Intravenous [rat] 29mg/kg
Intra muscular [rat] 373mg/kg
Oral [rat] 666mg/kg

This is the most current MSDS for Delta-9 THC [keep in mind this is not the data for marijuana, as in raw cannabis, but only the data for refined Delta-9 THC] but all of the LD50 data harkens back to studies done in the 70's, many of which were not set up in a way that would make the data definitive in any way.

For perspective: injecting anything - no matter how 'safe' in high enough quantities can be fatal.

2nd : Note the comment about monkeys not having an oral measurable level;

Acute Effects of Marijuana (Delta 9 THC)

16. Hmm what if you made a GIANT bong and filled the bowl pack with 1 pound of the most potent hash and you torched it and cleared it in 1 hit? then you should die.

17. That second link was actually pretty interesting. Answered most of my questions anyway.

18. its probably talking about 448g of pure thc. thats so much dude. when they measure in oil it useually doesnt include plant matter from the bud. im sure people have smoked more than that and eaten more

19. I'm kinda high but didn't it say that they did these tests and found these numbers by experimenting on rats? I would expect that rats would have a significantly lower tolerance than that of a human being.

20. #20
Last edited by a moderator: Nov 1, 2011
Yes exactly, if you go to the second link in ICGreen's post you can see that researchers noticed an increase in the LD50 of THC with larger animals. The article said that the researchers couldn't even establish an oral LD50 for dogs and monkeys because they were surviving doses over 3000 mg/kg, which is the equivalent of 1050 grams for a 70kg individual (2.3 lbs for a 154 lb individual).