How Long Does Marijuana Stay in the Bloodstream?

Health > What is medicinal cannabis?

This chart shows how long does weed or cannabis smoking or other use cause THC to remain in the hair and body and how much time after smoking you could be testing positive.

Many marijuana enthusiasts need to know how long does thc stay in the blood system?  The simple answer is: up to 30 days. It is rare that marijuana is detectable in urine after 30 days of abstinence. It may be detectable longer in hair, but such tests are infrequent and unreliable. However, many factors which we will examine determine specifically how long weed stays in your bloodstream. How Long Does Marijuana Stay in the Bloodstream

Smoking frequency, the biggest factor in how long marijuana lasts in blood

How often and how much you smoke is the biggest determinant of how long marijuana stays in your blood. A review published in 2006 by the University of Missouri showed some promising results for those anxious about how long thc will stay in blood.

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Most drug use detection for pot is done by means of urine testing. The scientific review found that for the average bud smoker, thc will leave the body somewhat quicker than commonly assumed.

For example, for a single use or infrequent use, THC-COOH, the metabolite tested for in urine, is not detectable after merely 72 hours for the average person.

For most chronic users, the average person will test clean in about one week after abstinence.

Most heavy users are looking at 10 to 21 days of abstinence before THC levels test clean.

Frequency of useHow long for clean test for average person
Single or infrequent72 hours
Chronic use7 to 10 days
Heavy Use10 to 21 days
All use Less than 30 days


Though some people on the extremes of their ability to store and metabolize THC may get wide variations, for the average person, marijuana stays in your blood for less than 30 days.

What determines how long does thc stay in the blood system?

stay in blood

How long weed stay in your blood system is determined by your biology, the amount and frequency of exposure, and the amount of THC stored in fat cells. Many users know that thc stays in bloodstream by hiding in fat cells, which then release variable levels of the thc metabolite thc-cooh (11-Nor-9-carboxy-THC) over time. This metabolite which results when the hash or cannabis you have consumed is processed by the liver, is what is tested for in your urine.

What to do before the test to reduce thc levels

Follow these steps:

  1. Reduce or eliminate calories and drink lots of water so the thc begins to flush from your fat cells. Do this at least 4 days out from the test.
  2. Drink lots of water to flush the thc out in your urine, at least 3 days out from the test, all the way up to test time.
  3. Re-feed. Two or three days before the test, raise your calories back to normal to stop the fat from burning and releasing thc.
  4. Pre-test. Get a marijuana test from your local drug store and make sure it’s negative before you go to the scheduled drug test. If positive, you will have to find a way to stall or re-schedule.

The amount of thc in your urine will be determined by how much weed is in your fat cells and how quickly it is clearing out of the fat cells, into the body, then into the urine. The rate of fat burning is determined by your diet and exercise. If you have a drug test coming up and a few days to prepare, it is advisable that you first fast, eat low or no calories for a few days so the remaining thc empties into the body, then drink lots of water to clear it out of the system. Before the test, you will need to put a stop to the fat burning by consuming sufficient calories. This will put a halt to the thc spilling out of the fat cells, into the blood and urine. Next, to dilute the remaining thc, drink lots of water. To recap, fast, hydrate, then refeed, and hydrate. This will flush the thc from your system and dilute the remaining cannabinoids before the test.

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What not to do

  • Don’t show up hungry (thc will leak from fat cells)
  • Don’t use masking agents (inconclusive tests make you look guilty)
  • Don’t go in thirsty (marijuana will concentrate in your urine)

Some people will try to drink masking agents to prevent the test from detecting thc. We advise against this because the test can sometimes discover the masking agents and also, an inconclusive test is sometimes seen as a failed test, especially if it is also inconclusive on retest. That’s the sign of a masking agent and suggests guilt. Since the scientific review we cited earlier suggests the average person will get rid of thc fairly quickly, it’s better to be prepared, clear the system out by fasting and flushing.  Then as the most important suggestion, buy a home-test from a drug store, and test yourself to make sure you don’t test positive before you take the scheduled test.

Also, don’t go into the test hungry and in fat-burning mode, because thc will be spilling out of your fat cells, into the blood stream, and into the urine. Instead, make sure you have been well fed and drinking lots of water for a day or two and on test day. If you are thirsty, your urine will be more concentrated and that could concentrate the thc and lead to a positive test.

Pre-test before your drug test

Don’t go blindly into a scheduled cannabis drug test. The drug tests for weed that you can buy from your local drug store is often the exact same test you will face when you get drug tested. So, make sure you test negative before you go into the test. If you are positive, try to reschedule your test, fast and flush, then pre-test again until you are negative. Then go into the rescheduled test. Although this method, fast, flush, and pre-test, will succeed most of the time, there is a small chance to test positive after having tested negative at home. This happens if you let your calories get too low right around test day and thc begins to leak from the fat cells that the body is burning for energy. So, remember to stay hydrated and well-fed on test day and keep up the good fight to make medical marijuana accepted so that in the future, such tests will be unnecessary.


— CARY, P.L. and — NATIONAL DRUG COURT INSTITUTE (U.S.), — The Marijuana Detection Window: Determining the Length of Time Cannabinoids Will Remain Detectable in Urine Following Smoking : a Critical Review of Relevant Research and Cannabinoid Detection Guidance for Drug Courts. — National Drug Court Institute.

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adultintheroom says:

Please define the parameters for “infrequent”, “chronic use”, and “heavy use”. Much of the article is meaningless without an understanding of your use of these terms.

Rene says:

I have over two weeks before I have to take a drug test. I have stopped smoking completely and exercise about 5 times a week and drink tons of water. Im 5’10 163lbs (not much fat) and my metabolism is pretty fast. Is it likely that I will pass?

Bob says:

First off, let me say you are luck for a reply. There hasn’t been any! lol, but i seen you commented recently and figured i would atleast reply to you as many don’t.
So….I would say you are still cutting it close. most employers want a urine test. THC can take 30 or more days as the metabolites can stay even up to 90 days in chronic or every day users. how frequent you smoke also plays a part as well as how much body fat and your metabolism. from what i ready you have many things working for you. low body fat and the fact you drink plenty of water and exercise 5 times a week. Its still risky though! theres always a chance. if you’re an occasional smoker….it might be in your system for up to 7 days and thats for the occasional smoker. much longer for chronic users. the fact you have over two weeks is definitely a PLUS! but again DO NOT SMOKE ANY LEADING UP TO YOUR TEST! if you do i guarantee you will BE F***ED! Your chances remain atlas somewhat good right now to atleast test below their threshold level and if you do you will be negative. Given you don’t drink a shit ton of water before your test. if its diluted some places won’t accept it. and you may have to retest. also when you drink somuch water you piss clear…. A DEAD GIVE AWAY YOUR TRYING TO CLEAN OUT! also, when you drink hell of water it depletes your creatine levels which they also look for. So My advice…… Keep working out as you are 5 days a week, but i would stop working out about 2-3 days before your test. The given reason is because when you work out your body re-distributed thc and its metabolites back into your system as you workout. thats why you don’t work out 2-3 days before your test. you don’t want to re-distribute whats left in your fat cells back into your urine before the test. Also, keep drinking hell of water, until about a day or 2 before your test. the day before still hydrate your self well but not cramming it down like you will be in the weeks to come before your test. I would take a multivitamin everyday. because your drinking smooch water in the weeks prior to your test you levels are going to be consistently low because you are drinking somuch water. the multivitamin will bring color to your urine back. along with keeping your levels somewhat there. Next Creatine: buy some creatine mono from walmart. I would take 5 grams the days before and the day of the test. this will help bring your creatine levels back up before your test due to the amount of water which depletes your creatine levels. Which they also look for. So you need color in your urine and your creatine levels need to be there. Both a must! As an insurance policy, i would buy a detox drink. I would buy “The Stuff” Note that this is only a mask for leftover metabolites in your urine to help pass the test undetected. Be sure to follow the directions on the bottle. The day of your test. get up early before your set time to take your test. about 4 hours earlier. Drink it. Be sure to follow the directions on the bottle. Urinate 3-4 times before your test and then take the test. If you do these things I’m almost certain you will pass. UNDER NO CIRCUMSTANCE DO YOU GIVE THEM YOUR FIRST MORNING URINE. These contain the most metabolites left in your system. Thats why you want to get up early to drink the detox drink and then urinate 3-4 times BEFORE your urinate for your actual drug test. The is always a risk! but with the time amount that you have…id say your chances are good if you follow the instructions i have laid out for you. Also, Cranberry juice…..DRINK IT! not the sugary ass kind. The less sugar and fats you take in, in this period the better. Eat green foods. Salads if you can. Eat healthy. try to stay away from red meats. they are harder to digest and they slow you metabolism down. you don’t want that since your metabolism is fast. We like that. The faster your metabolism the faster you process whats THC and leftover thc out of your body before the test.


More Information: i recently had a little over 2 weeks to get clean myself. i took a urine test, I’m sure that my piss was diluted, i made sure my color was good, but had little knowledge on the creatine levels which they look for. I didn’t fail, but it made me look a little suspicious. they had me come back to look at the test. the thc line was negative. however it was just a little bit faint. let me be clear. The line was there. i could see it from a distance. it wasn’t like i had to get up on it very close to see. so by faint i mean it was definitely there for negative, but was a little faint than the others which tested for cocaine, etc. etc. which told me i had probably barely reached their cutoff level for thc.
I wasn’t sure what they were going to do. The fact that they had called me back…..i was like shit……here we go. but IF I WAS POSITIVE. they would have told me for sure. further testing wouldn’t have been done, and thats it. Bummer.
But that didn’t happen.
Now they wanted a blood test.
I was quite surprised! i figured maybe a re test for urine, but nope. a blood test!
My guess on why: because my urine was probably diluted, (but i had color to my urine)(assuming my creatine levels were pretty low) because i did drink hell of water up until the day before….they wanted to see if i had either tampered with the urine(which i didn’t) or was trying to dillute(which of course) so my guess is they wanted to see if i had marijuana in my system at that point and time and was trying to just dilute.
Now think…..metabolited stay in your urine much much longer than blood. for someone with thc abstinence of 2 weeks or more your blood should be clean by now. so they shouldn’t find anything. Research i have read ( and i have read everything under the sun!) says that even for chronic users it should be out of you blood by 2 weeks, even less for occasional users (5-7 days)
In a way i am glad that i didn’t have to retest for urine and that they did do a blood test because i haven’t smoked for more than 2 weeks. should of had enough time for my blood to be clean. (I am a chronic smoker. Every day!) (5-7 times a day) (bowls) with similar to you in body weight and metabolism. maybe just a bit taller.
Thats just some more info from my experience. (YOU ARE GETTING GOLD HERE!)

Note: Just so you know the unexpected CAN happen!
I am currently waiting for my results and should hear something today! id say if they are confirming of the blood test. i have a lot better chance at passing as there are detection time windows for blood test.
Thats why when ppl get into accidents, they want blood test to see if they are currently under the influence or recently have been.
But with all the research i have ready…..they already had missed that detection window for blood by more than 2 weeks.
Id say my chances a very good. Still a risk, but very good.

If you want to avoid this possible happening to you you can always just do what i should have done. I would have did it if i had know for sure.
You really can’t go wrong either way…urine or blood. it cleans both! This is the #1 product i have found. ITS THE BEST. a bit expensive but worth it
Its called “Tox Rid”
If you are a heavy smoke, i wouldn’t recommend the 3 day. If you have 10 days… the ten. Order it immediately. stay hydrated (you don’t need to cram water like you have been without tox rid, but do stay hydrated and still urinate.
But if you want a sure 99% chance of passing….
I Hope this forum helps somebody and informs you that even the most unexpected can happen! I never expected that blood test!
Hope this helps! Good luck Troopers!

John Em says:

Hello! Say if one were to be a frequent user for less than a month and only took on half-full hit from a hitter per day. Would this effect the time which one would need to detox, or would the frequency still have the same effect?

Kris says:

Hi just wondering did you pass the blood test ??
Thanks regards

Joey says:

If anyone needs to get clean fast go to your local gnc and buy niacin it has a silver cap dont buy the orange bottle its something different. When u take it feels like ur skins burning but drink plenty of water and when u can take it and not feel the burning sensation your urine is usually clean.