That’s about it. If I did a few one-hitters in the parking lot of the Lutheran Church, then went in and was “needle-in and blood-flowing” within 15 minutes, would the THC survive in the blood to transfer to another person?
Probably not, there might be some THC in the blood, but there won’t be enough to get anyone a “buzz”. Consider this, a normal joint has about 20mg of THC in it, of that, only about 20%, or 4mg, reaches systemic circulation. There is on average 10 pints of blood in an adult male, they take 1 pint on a blood donation, or 1/10.
So, if you are smoking the pot while they are taking the blood, there would be on average about 0.4mg THC in the donation. And that’s just at first smoke. THC is rapidly distributed to the tissues, and the blood is metabolized by the liver. THC is cleared out of the blood really fast (it’s the metabolites that drug tests test for).
You actually have two different questions in your OP, and I’ll address both of them.
- “Would the THC survive in the blood to transfer to another person?”
Yes. THC and its derivatives bind to plasma proteins as they are transported in the blood. One study* shows that the vast majority of the chemical is transported on blood albumin and virtually none on erythrocytes (Red Blood Cells). Thus, you’d find THC in the plasma but not in the hematocrit of transfused blood. Therefore, THC will probably only be present in detectable levels if the original plasma from the marijuana smoker is transferred along with the cellular components.
*Giroud C, Ménétrey A, Augsburger M, Buclin T, Sanchez-Mazas P, Mangin P. 2001. Δ9-THC, 11-OH-Δ9-THC and Δ9-THCCOOH plasma or serum to whole blood concentrations distribution ratios in blood samples taken from living and dead people. Forensic Sci. Int. 123 : 159-64
- “Will [the transfusion recipient] get a buzz?”
Probably not. Pharmacokinetic profiles** of plasma THC after smoking show that it exhibits classic exponential decay with a peak plasma level of 120 ug/L, and a mean half life of around 1.2 hours. However, plasma levels of THC drop sharply immediately after smoking, to around 17% of peak levels after the first hour. Even if you walk into a donation center and are immediately processed, this will be at least half an hour until blood is actually being drawn from your body. Once the recipient has your blood transfusion, some of that plasma THC will be distributed to the fat, and and even smaller amount will reach the brain where it can render its physiological effect. So, to sum up: small amount of THC in blood at time of transfusion, not all of the blood you have in your body is donated, not all of the transfused THC will reach the brain = unlikely to have a noticeable “high”.
** Toennes SW, Ramaekers JG, Theunissen EL, Moeller MR, Kauert GF. September 2008. Comparison of cannabinoid pharmacokinetic properties in occasional and heavy users smoking a marijuana or placebo joint. J. Anal. Toxicol. 32 : 470,477(8)
Will the recipient fail a drug test?
Over what time frame? If you’re talking within several days to weeks of the transfusion, then probably yes. THC metabolites are stored in fat tissue, and the amount of THC in the transfused blood is probably enough to register on a test. This is pretty speculative though, so this is probably not a recommended way for you to edge out the competition for your next job interview. 
People forget that blood is just a fraction of the total fluid in your system. (The blood is just the fluid with the blood cells in it.) So the ratios are even more unfavorable.
Ha! That, they probably will.
Help! I need a transfution stat
How about the reverse? Could a chronic pot smoker get a blood transfusion and test clean in a relatively short time frame? I suppose it depends on the limits of the transfusion and the lower limits for testing positive.
Can I barge in with a related question? How stoned would I have to be to pass along a buzz to a blood recipient, and would the intensity of the buzz be less if the blood was stored a longer period in a fridge?
Dear Mythbusters,
I have a great idea for a future episode…
Wow, if you don’t send them an email like that, I will!
I was drinking heavily at a festival of sorts in Miami where there was a van from the local blood bank (not Red Cross, Community Blood Services of South Florida, I think) and they said I was fine to donate even with whatever BAC I had at the time, the alcohol wouldn’t make it to the recipient.
No. As mentioned before, THC and its metabolites are quickly moved out of the blood and either stored in adipose tissue or detoxified by the liver. Trying to pass a blood test by transfusing blood from a clean person to a chronic marijuana smoker is about as efficacious as trying to eat a bowl of soup with nothing but a pair of chopsticks.
Also as mentioned before, you have to consider at what point after smoking are you donating the blood. If you are donating very soon after inhalation of marijuana smoke, the best answer would probably be “many”. Based on some very rough estimates (this being purely speculative), I would probably wager 50-100 joints…not a practical amount for someone to have in one sitting.
Since most of the metabolism of THC is done by a variety of cytochrome P450 enzymes in the liver, I don’t think the amount of THC in stored blood would decrease significantly in storage.
So I could maybe get someone stoned AND set a Guiness record for pot smoking! Excellent.
What about pot and breastmilk? Say someone had really good tickets to a P-Funk concert, a hotel room for the night, and a grandmother staying at home with the baby. Joints ensue. Milk is expressed via a pump. In order to avoid passing any THC or other metabolites to the child via breastmilk, how long after the last toke should the milk be discarded? Hours? Days?
What, like Keith Richards?
In theory, what about pot brownies (in theory)? Hypothetically, I imagine that might be a method to get a larger amount of THC in your blood stream more thoroughly (hypothetically), or am I just blowing smoke?
This is just getting ridiculous. (Serious answer: I don’t know that much about production of breastmilk and whether or not breast tissue filters out components from the blood, so you’re on your own about a WAG.)
True, the pharmacokinetics differs based on the method of exposure. I don’t think ingestion pot brownies would make a difference on the conclusions I’ve stated so far. If anything, pot brownies would be a LESS effective way of getting your transfusion patient high because absorption of chemicals and nutrients from the GI tract is a much slower process than inhalation which is nearly instantaneous.
I don’t know, but I’m wondering if Dracula ran into this problem.
Isn’t someone on the receiving end of a blood transfusion fairly likely to be pretty loaded on painkillers already? Or, I suppose, ill enough that no effects would be likely to be felt anyway.
I’d be curious to see any future research on transmission of cannaboids through breastmilk. With the greater use of cannabis as medicine, one of the biggest reasons I’d like to see it moved down the “schedule” of illegal narcotics is to open it to such research in the US. I’m happy to see the number of medical marijuana states growing, but I’d really… really like to see some competent research on the subject.
Going slightly off-topic, I’m not sure I understand the ban against research on schedule 1 narcotics anyway.
Actually, the pharmacokinetics don’t really change based on route of administration. The only change is in the bioavailability. About 20% of THC that is in a joint reaches systemic circulation, while only about 10% reaches systemic circulations when administered orally. The difference is due to first pass metabolism effects in the liver. THC is well absorbed by the intestines, but get rapidly converted to its non-active metabolites in the liver.
However, your conclusion is still correct.