How Long Does Weed Stay in Your Blood

Whether you’re using marijuana for recreational or therapeutic purposes, you might be wondering how long does it stay in your system? How long does weed stay in your system and make you high? What happens when you’re up for a drug test? Will weed stay long to get detected in the blood? Let us answer all these questions about blood drug testing and more in this short but meaningful guide.

How Long Will Weed Show in a Blood Drug Test?

How long does marijuana stay in blood? Weed may be detected using different tests. The most common methods are urine drug tests and saliva tests but for accuracy, a blood drug test is the best. Weed and its metabolites can show in a blood drug test for up to 36 hours. It means that you might test positive in a blood drug test after two days or receive a positive THC test.

When Are Blood Drug Tests Used?

how long does weed stay in your blood

Blood testing is not commonly used compared to urine tests. The most common methods used are urine testing and saliva testing because these are easy to perform and are cheaper. It’s also easier to determine the results in urine tests and saliva tests as the test specimens are simply compared to a color chart. There are home urine and saliva testing kits available for anyone to use.

Highly-Specialized, Accurate Tests

Meanwhile, blood testing is highly-specialized and is performed and evaluated in a laboratory. Blood tests can detect marijuana or tetrahydrocannabinol the psychoactive compound in weed and other metabolites. These tests are very accurate and can determine other drugs as well.

Blood tests are best for chronic users, chronic cannabis users, regular cannabis users, infrequent users, and all kinds of marijuana users. Blood testing is also the most common test in drug abuse cases and when chronic cannabis users preclude testing. Addiction treatment or drug abuse treatment can finally happen after users test positive for weed.

Hard to Cheat

It’s very hard to cheat on a blood test compared to other drug tests. In urine testing, users can drink detox products to cleanse their systems. Some may also use fake or synthetic urine especially when there’s no time to detox. Still, others try to use natural remedies like cranberry juice, lemon juice, water, and others to dilute urine. In blood testing, the best way to pass is to abstain from taking weed. Chronic users may not pass blood testing for THC as it can stay in your system longer.

Are Blood Tests Better than Urine Tests?

how long does weed stay in your blood

Blood tests are better than urine tests in many ways. It is more accurate than a urine test and can detect marijuana metabolites of THC in the blood more accurately. Blood tests are also fool-proof as you cannot cheat on a blood testing.

Meanwhile, there are some disadvantages to using blood tests. THC is present only for a very short time in the blood and offers a brief detection window. Blood tests are also very expensive which is why these are not commonly used.

The time marijuana remains in the blood is so short that anyone who smokes marijuana or those who smoked cannabis will have low to zero plasma THC concentrations in the blood after a few hours. However, those who take marijuana regularly or have prolonged drug exposure may take time to remove THC in the blood.

Hair Testing and Saliva Testing

Aside from urine and blood tests, hair tests are also used to determine weed use and history. A hair test can find out how long has a person used cannabis. Hair tests are used in drug abuse screening, marijuana addiction treatment, and therapeutic drug monitoring. Light users and heavy users may test positive in a hair test but users exposed to secondhand marijuana smoke are less likely to test positive.

Meanwhile, saliva or oral fluid is also used to prove cannabis plant consumption. This test can determine THC levels aside from marijuana use. All these drug testing methods are useful in substance abuse/substance use treatments, marijuana withdrawal, and in patients abusing prescription drugs.

How to Prepare for a Drug and Alcohol Review

how long does weed stay in your blood

Testing for drug and alcohol dependence may be announced or unannounced. Employers may include drug testing as a requirement for employment or this may be done randomly in a year for regular employees. It’s easier to prepare for a standard, announced blood test but an unannounced test is another thing.

The key to passing all types of testing (urine test, blood test, saliva test, and hair test) is abstinence. Use cannabis occasionally so it’s easier to remove the drug from your system in case you need to pass a drug test. In a blood drug test, you need to be free from weed at least three or more days before the test. 

Hydrate Yourself

Hydrating the body is a natural way to get rid of toxins, THC metabolites, and unwanted chemicals especially when smoking marijuana and alcohol abuse. It is also the best way to remove THC in the kidneys and blood. So, instead of taking only a few glasses of water, try taking 8 to 10. You may also drink fruit juices, shakes, and soups, as these are liquids too. If you smoke marijuana and plan to use detox liquids, drink the same amount of water to help your body flush out toxins. Never drink alcohol to counter the effects of weed.

In the case of alcohol, you can remove alcohol metabolites by drinking more water as well. If you’re helping a friend that’s heavily intoxicated, try offering water, fruit juice, or a hot beverage.


THC is stored in the body’s fatty tissues/body fat and thus, one way to remove these is to exercise. If you have time to spare before a test, try running, swimming, cycling, brisk walking, or jogging to help get rid of THC in the fatty tissues/fat cells. If you regularly use cannabis, try exercising daily to help your body metabolize THC faster. And of course, abstain from weed as you exercise. 

Using Detox Products

The internet is a shopping mall for weed detox products.  The most common ones are weed detox liquids or drinks that you take a few hours before a scheduled test. These drinks claim to cleanse the body, remove toxins and clear out THC only when all the instructions are followed very closely. Most detox drink products contain natural ingredients such as vitamins, minerals, and creatinine, which mask urine.

There are also detox pills that help get rid of THC and other toxins days or weeks before a test. These detox pills are also made from natural ingredients and are often used together with detox drinks. Meanwhile, detox kits are sets with drinks, pills, and fiber sachets. These kits come with strict instructions and are mostly customizable according to your weed habits.

Using Natural Methods

Many users prefer natural methods to remove toxins and THC. These methods may or may not work so use these with caution if you wish to pass a blood weed exam. If your cannabis consumption is high and your body mass index is high, use tested methods instead of natural techniques to get rid of THC metabolites.

One of the most popular natural methods is using cranberry juice. Many say that cranberry juice contains vitamins and minerals that can help reduce THC in the body. Also, cranberry juice can replenish lost nutrients.

Just like cranberry juice, lemon juice is also a popular natural method. It is said that lemon juice can help neutralize the body and get rid of toxins faster. Another natural method is drinking tea as it can help burn fat and metabolize THC.

Final Words

Weed can stay up to two days in your blood. If you want to pass a blood test, stay off weed for at least three or more days. You may also improve your chance of passing a marijuana drug test by drinking more water, exercising, and using detox products. Use natural methods with caution as these may or may not work to get rid of THC.

Bikas Gurung

Bikas Gurung is a human rights activist representing International Drug Policy Consortium (IDPC) and United Nations Strategic Advisory Group on drug use. He received his Master’s degree in Public Health from Chulalongkorn University in Thailand and has been recognized for his work by winning "The Best Film Award" at the 2013 Harm Reduction Conference in Vilnius, Lithuania.