Robert Bergman

May 9, 2019

Both marijuana smokers and employers may find this article quite helpful, considering how very common it is that employers require drug testing before, and even during, employment.

This article provides useful information and history that you may want to know about marijuana and blood testing, so pay close attention.

Drug Detection Laboratories Inc., states that the methods used to test the blood for marijuana offer information that shows whether the person has been using marijuana. Marijuana has THC, which is a chemical compound within cannabis. THC can stay in your bloodstream for as long as 4 hours after consumption if you do not smoke on a regular basis. If you are a frequent marijuana user, then it takes a long time for this substance to leave your system, due to the residual build-up of THC in the bloodstream.

This build-up of THC happens because it is fat-soluble. Due to this fact, it remains detectable in urine for quite some time.

Marijuana drug history

Cannabis drug history

People have been using marijuana to reach states of ecstasy since as far back as A.D. 500, says NARCONON International. So we are not doing anything new by using this plant for recreational purposes. It is likely that people have been getting high since the beginning of time.

There are even Chinese medical writings from 2737 B.C. that mention marijuana’s medical benefits. The Spanish are the ones who brought this much-loved herb to the United States in 1545. Growers have used marijuana for fiber in clothing, and this did not change until the 1800s when cotton become popular. During this time, doctors were giving their patients marijuana for labor pain, rheumatism and nausea.

1914 was the first time Americans were subject to any drug laws. The Harrison Act made using drugs for non-medical purposes illegal. However, it was almost 40 years until drug testing tools were made available.

As technology for drug testing began to advance, the Forensic Toxicology Specialist announced that blood testing equipment could reveal the presence of cannabis. The National Organization for The Reform of Marijuana Laws claimed that blood screening discloses any recent use of non-medical drugs. THC can only stay in your blood stream for just a couple of hours. For this reason, it makes sense that an automobile driver involved in an accident would be tested immediately afterward to determine if they were under the influence. This is most likely done using the finger prick method.

Things to consider

Marijuana blood drug test

Blood testing isn’t the best way to determine if THC is in the body. Urine tests have proven to be much better for this. On the other hand, blood tests are better at showing the levels of drugs present at that very moment. If you used marijuana in the last 20 days, then a urine test will reveal this information. When you have THC levels above 3.5 to 5 ng/mL this is considered impaired.  You will usually see these levels within an hour after smoking. Now, of course, this differs for people who smoke often and have a higher tolerance. These people are probably not going to be impaired at those levels.

So someone who uses weed on a regular basis will have around 5 nanograms of THC floating around their body all the time. The more you use it, the longer it takes to dissolve.

According to the National Highway Traffic Safety Administration, more people are consuming weed than any other drug worldwide. With all the medicinal and meta-medicinal benefits of smoking marijuana, this is not surprising at all.

Why test blood for marijuana?

Why test blood for cannabis

Blood drug testing has been found to be:

  • costlier
  • incapable of revealing consistent use
  • potentially less reliable

Yet, it still lets police officers, employers, and the government know that marijuana is present in your blood. With urine and hair testing available, they do have other ways to get better, more detailed information on your weed consumption.

There has to be some reason so many employers want you tested for cannabis use, right? Well, according to the Drug Policy Alliance, marijuana encourages sedation, ataxia, short-memory and euphoria. Smoking cannabis leads to enhanced blood pressure and tired-looking red eyes.  They feel that using marijuana for personal reasons has no positive effects in the workplace, and when driving a vehicle. This is the basis for employers wanting to test you for marijuana usage. In their eyes, marijuana users could likely be slacking on the job.

Testing Rules May Vary by Job

In states where marijuana is legal, employers can still decide whether or not to test. While this is great for those who work at companies that do not test, it also means some people could lose their jobs for using marijuana over the weekend. Drug testing may occur as a condition of hiring, on a regular basis, or randomly.

Even in companies with an established drug test policy, it is also common to see testing rules vary by jobs. In the same company, a janitor may get tested weekly, while an executive is never tested. The laws do not protect the janitor from losing their job, as businesses can also decide who they drug test.

You will most likely get tested if you work in manufacturing, logistics, or construction. Those who work as truck drivers, pilots or with the Federal government are also likely to get tested.

If you want to make sure you will pass the test, try TestClear.com! Get 10% off with the coupon code TestClear10.

Things marijuana blood drug tests do not reveal

Things marijuana blood drug tests do not reveal

Taking a blood test will not show whether you have ingested, smoked or vaporized marijuana. When you smoke cannabis, this causes you to be impaired much faster, than if you were to ingest it. This happens because THC spreads quickly once it enters the lungs. As for edibles, it does not work that way since the overwhelming majority of it dissolves into the liver, and never enters the bloodstream.

How strong the marijuana is will all depend on the strain you are using. How you choose to consume it, changes the level of impairment.

Legal limits for driving after smoking

Legal limits for driving after smoking marijuana

Some states have a driving limit of 5 nanograms per milliliter of blood. Some people say that this is way too low for people who use it on a regular. On the other hand, some people are far stricter in their opinions of this stating that having only 1 nanogram is enough to consider someone impaired.

Some of the reasons people are concerned about driving while under the influence of weed are due to THC’s effect on perception, paranoia, and how fast someone can react. Driving high on weed is not any riskier than drunk driving.

It could take a while before legal principles and science are in one accord. In the meanwhile, understanding what’s out there could keep you out of trouble.

Thanks for reading. Please leave comments or questions below and don’t forget to download my free grow bible.


The founder of I Love Growing Marijuana, Robert Bergman, is a marijuana growing expert that enjoys sharing his knowledge with the world. He combines years of experience, ranging from small-scale grows to massive operations, with a passion for growing. His articles include tutorials on growing... [read more]


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  1. By How To Pass A Marijuana Drug Test

    ,17 Feb 2016
    […] Despite these facts and studies, some states are trying to establish a zero-tolerance law for driving with marijuana in your system. Others are just trying to establish a numerical limit of some sort, despite the fact that people with […]Read More
  2. By Lynn Bellus

    ,16 Mar 2016
    Our employer uses the urine test to detect drugs. I've nver used marijuana before, but my constant pain is telling me to go the natural route rather than a multitude of pills, so i'm now growing it. I'd also like […]Read More
  3. By Jack Barrie

    ,06 Feb 2018
    I know someone that was stopped at the roadside and tested positive for cannabis a thin blue line. This person last smoked a J at 9pm, she was stopped the following morning at 8am, tested at 9am and had a […]Read More
    1. By Gavin Greenwood

      ,03 Apr 2018
      What happened with your friends results?
  4. By Marty

    ,22 Jun 2018
    I haven't smoked in 39 days . Had a blood test today . I am a 150 pound female.. who thinks I'm going to pass ?

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