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Drug Testing Gets Complicated: Exercise Causes Spike In THC Levels

By on September 11, 2013
Exercising before a drug test increases your chances of testing positive for marijuana (Photo: Rob Annis/Lifehacker)

Exercising before a drug test increases your chances of testing positive for marijuana (Photo: Rob Annis/Lifehacker) – As if marijuana testing wasn’t complicated enough, research now shows that exercise can cause THC levels in the blood to rise.

The problem with testing for THC is that – unlike other drug metabolites – THC is stored in the fat cells of regular marijuana users. Previous studies show that it can stick around for about a month – in some cases, up to six months – since last use.

Now a team of Australian scientists have shown that exercise can lead to a spike in blood THC due to the burning of fat. Their results were published online in the journal Drug Alcohol and Dependence.

Lead author Iain McGregor, a professor of pharmacology at the University of Sydney, explained the implications of his findings to ABC.

“Someone subjected to workplace or roadside drug testing after a visit to the gym could end up testing positive despite an absence of recent cannabis use.”

What’s more, the study showed that people with higher BMIs experienced this effect to a greater degree. More obese individuals had the highest levels of THC in their blood, regardless of how much cannabis they used the previous day.

“The more fat you have in your body the bigger the reservoir you have for THC,” explained McGregor.

Researchers recruited 14 regular cannabis users and took blood samples from them before and after 35 minutes of exercise on a stationary bicycle.

While the spike in blood THC did not seem to cause a high, it was significant enough to be noticed on a standard drug test.

McGregor believes the findings have widespread implications.

“Someone caught in a bad car accident … the stress could cause them to burn fat and raise their THC, and they could give a positive drug test.”

The team plans to repeat the study on a larger group of patients in order to provide further insight into fat burning and THC levels.

The study was published ahead of print and received funding from the National Cannabis Prevention and Information Centre (NCPIC) and from the National Health and Medical Research Council of Australia.


  • Robert Brown

    I’m an average pot smoker and was curious as to how much THC is metabolized after 1-2 hours of aerobic/anaerobic exercise. I also am an athlete

  • IsThisSomeKindOfSickJoke

    I quit smoking weed 2 months ago and started working out 2 weeks ago. I tested positive this morning. What a great reward for making new healthy choices in my life. The UA Tech looked at me like I was Cheech with a blunt burning in my mouth.

    • ME

      JUST FIRE UP .

    • yayaya

      Use “Sony 7″ its in any Fred Myers health food section.
      Looks like, well you’ll find out,lol, but drink it in water.
      Avoid all sugars cause sugars are what?
      Converted into fat, what breaks down fat the pancreas,ok.
      New topic…lol
      The pancreas is the key, everything is very time release in the body dont do anything stupid like ingesting bad chemicals or OD’n on things you dont know about to get a job.
      Research it!

      • Dr . Greenthumb

        I can’t get it in Michigan. Wish I could find it. It’s the best

        • nixon

          Just got some good AK47 buds from Dr Peter am now high here in FL with dude and dudette will be coming back to him soon for more

  • jiggy who

    My THC levels has risen from 115 (03/23) to 208 (04/06) in 14 days..but I have not smoked since (02/23)..been working out lost 25 pounds during this time..thinking this was the way to get rid of the THC..failed the drug test on 03/ I need to test again on 04/28 confirmation test..and the only people that know I have not smoked since Feb 23 is me and Jesus…how can I explain this to the MRO..

    Weed is nice, but the day I get clean : I am staying clean..I can’t imagine how many kids who THC levels my raise due to weight lost. Go to jail because their PO believe they are still smoking..

    They need to find a different method to test THC ..perhaps test the actual THC rather then the metabolites..

    PS: I know I should have never been smoking in the first place..but goddam! Now the MRO gone think I lost my mind when i tell him i been clean since feb 22..but my second drug test is dirtier then my first… boy boy boy

    • the watcher (ewww!)

      Sony 7, read yayaya’s shit.

  • Travis Fisher

    I used to work at a drug testing lab where we would test hair samples instead of blood or urine. It’s much harder to falsify and it wouldn’t be affected by exercise like blood.
    We would cut off about 1/2″ length of hair right above the neck. That would give use the last month of hair, so you needed to be clean for the last two months if you want to pass.

    • Graeme

      No, but hair tests are easy to beat; bleach with the strongest grade hair bleach you can find, do it two days in a row (or even three if your scalp can stand it), then re-dye your hair back to it’s natural color and use a hot oil hair treatment to repair the damage from the bleach. If you do it right, the bleach should kill virtually any traces of anything in your hair.

      Now a blood test? That’s hard to beat, but I’m working on it.

      • bla

        Yer nuts, going that far to pass a test…lol
        Bleach your hair, most tests are UA’s.
        The hair follicle test is spendy to a cheap skate company or a out patient in treatment.

    • rcb

      what analyte did you test for? if it was a metabolite, then the hair will/would still test positive even after cessation, since it incorporates the metabolites that are released from the fat cells into the blood.

      • yayaya


        • yayaya

          Fats cells dont fucking release anything, its processed by the pancreas that breaks down fats then hits the blood.

          • yayaya

            Pancreatitis is when you cant break down fats or stored sugars.

          • yayaya

            You cant metabolize with out a pancreas

          • yayaya

            So, break’n I down for ya.
            Use Sony 7, workout normal, as you workout drink your water with sony7 then keep drinking water eat low fat foods.
            You’ll loose weight this way too but make sure you replenish your body of nutrition it strips everything safely by obsorbing everything then you poop it out. By by THC!

          • skrewed

            so how many days before a test should you use sonneseven?

      • yayaya

        Fat cells are like a suit case, the pancreas opens that suit case up then and breaks down fats to hit the blood correctly, metabolism.

    • yayaya

      Am I right sir, you work for a UA joint correct?
      You get all the THC from fats right?

  • Rayden43

    I was an excessive smoker, smoked the really good stuff for over 3 years strait, and reggie for 9 years before that. I’d say I probably smoked 3-5 times a day on the good stuff and 5-8 times a day with the reggie. I have been smoke free for 84 days now. I failed a urine test after 45 days so I figured I would give myself 75 days. I did a lot of cardio and strength training exercises since I quite almost 3 months ago, lost 25lbs! Feel great and had high spirits so today(day 84) I went to purchase a First Check home urine test for marijuana….and it’s still positive! Speechless….trying to figure out how to get rid of this crap! Any other ideas out there besides giving it more time?

    • PchMasFlx94

      Try this. For six days drink these beverages in this order. For the first two days drink at least 6 glasses of cranberry juice a day. Repeat this same process for the next two days but switch out cranberry for orange juice, and again 6 glasses a day for two days. Finally repeat for the last two days but now switch to water. Try to space these drinks out between meals if you can and they have to be the only thing you drink that day. I had a friend on probo that would do this a week before his test and he would always pass and that guy was a fiend with his weed. He was a normal built average sized guy though so for heavier built people im not sure if theyll need to continue the process a little longer. But I hope this helps if you try it please tell me the results id like to hear them

      • yayaya

        You are drinking sugars, sugars are broke down to fats THC is stored in fat right?
        What controls the fats in your body look it up?
        The pancreas.
        “Sony 7″ baby its my true blue!!

        • kirktwerk

          sugars do not turn into fat, only fat and protein do, sugars make triglyceride which is not something that makes u a fatter person

        • Alec

          sugar just spikes insulin which stops fat burning. It does not turn into fat. just makes you fat.

        • Maxx

          Its also got antioxidants which break down toxins in your body and thc is considered a toxin

    • yayaya

      Clean the pancreas that is the secret.
      They get all the drug test stuff from the pancreas, I’d use SONY 7 a pharmaceutical grade volcanic ash and clay you ingest.
      Goes by the spoon full by weight mixed in water or juice. Safe and cleans you out in 2 to 7 days, police firemen and all the people the put you away use tho shit so they dont loose there jobs big a dick head busting pot heads and eating they’re cake too.

      • yayaya

        Sorry spell check on my cell

  • alejandro

    So if I’m obese I can’t exercise because my thc levels will rise.

  • Hysen Berisha

    Obviously you’ve been sitting on your ass and just consuming McDonalds and nothing but high fat calories. Duhhhhhh what do you think?

    • yayaya

      Yer not funny, but yer funny looking…

  • Dr. Greenthumb

    I’ve known this for 10 years. And people always looked at me like I was stupid.
    The only time I’ve ever tested positive for THC I was in weight loss.

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  • Josue

    I quit smoking while I was on probation for about a year. I got off then smoked for about 2-3months I say an ounce a week. I been clean for about a month but I’m still dirty. I’m trying to get in the military but The only problem is I’m dirty. Any advice on how much longer I should wait, or anyway I can speed up the process.?

  • Josue

    I quit smoking while I was on probation for about a year. I got off then smoked for about 2-3months I say an ounce a week. I been clean for about a month but I’m still dirty. I’m trying to get in the military but The only problem is I’m dirty. Any advice on how much longer I should wait, or anyway I can speed up the process.?

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  • meca Douglas

    OK I have not smoked weed for about a month now how or why can my THC levels go up n down as if I’m still smoking weed it’s is getting me mad cuz the cps Worker thinks I’m lieing

  • Thatguy

    I’ve smoked all my life until recently- Anyway it took six months for it to be completely out my system – I smoked it for 18 years 20 times a day, but still..


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  • Gaby

    I will b clean for 14 days when I can to go give my drug test I now weigh 170 I lost some weight in the 14daya bc I detox ed.. I’m still scared I’m going to come up positive, I smoke for about a mth maybe longer wasn’t everyday and wasn’t alot maybe a hit to 2. Please do u think I will b clean?

  • Chris Garver

    I am in a treatment facility and i graduated on thur, i took a drug test on wed and it came back clean then on fri i started IOP and i took a drug test fri also and it came back with a level of .02. I cant understand how i’ve been testing clean for 4 months and now all the sudden i test .02 on marijuana. What the hell, could it be because i have been doing alot of walking? Please help me understand.

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