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Everything Cannabis Users Should Know About THC Blood Tests

Hundreds of workplaces and police offices are searching for reliable ways to measure THC intoxication in employees and drivers. There are even a few prestigious universities pouring money into THC breathalyzer technology.

To date, however, scientists are having a difficult time inventing the ideal THC detection test. While each analysis technique could detect THC and associated metabolites, they can’t prove a 1:1 correlation with a person’s physiological state. In fact, there’s still a hot debate over just what amount of THC constitutes intoxication.

Unlike drugs like alcohol, THC could remain in a person’s system long after they’ve used marijuana. So, while most drug screening methods can give a sense of a person’s prior marijuana use, they may not prove a patient’s current mental state.

However, some researchers argue that marijuana blood tests offer a clearer glimpse into a driver’s current THC intoxication. Although marijuana blood tests aren’t standard, they are a viable screening method. As marijuana blood tests become more influential, cannabis customers should know how they compare with other screening methods.


What is the Difference Between a Cannabis Blood Test and Urine Test?


Arguably, the best way to understand cannabis blood tests is to contrast them with the more common urine samples. Generally speaking, cannabis blood tests focus on delta-9 THC concentration, while urine tests look for THC metabolites like THC-COOH.

Why do these tests specialize in different THC compounds? Short answer: THC absorption rates.

Soon after a patient inhales cannabis, delta-9 THC rapidly enters the bloodstream. In fact, recent tests suggest THC is detectable in blood plasma 3 – 10 minutes after a person smokes cannabis. However, these delta-9 molecules are quickly converted into numerous THC metabolites.

Both delta-9 THC and its associated metabolites are fat-soluble. By contrast with water-soluble nutrients, fat-soluble compounds don’t dissolve in water and quickly pass in a person’s urine. Instead, cannabinoids like THC are stored in fat cells and only gradually released into the kidneys for excretion.

Interestingly, the more fat a person burns during a workout, the more THC floods their body for excretion. This is why some studies suggest exercise increases the odds of a THC positive reading, even if someone hasn’t smoked cannabis for a few days.

Urine tests are usually better at detecting prior cannabis use, while blood tests could capture the immediate “delta-9 spike.” In fact, blood samples may give analysts a precise picture of the THC actively influencing a person’s endocannabinoid system.

Scientists have begun comparing THC blood test results with urine samples to test these theories. Most results suggest blood samples can accurately tell the active amount of delta-9 THC, but only briefly. Urine tests, however, could detect THC metabolites days or weeks after cannabis use.

For instance, research from the University of Iowa examined THC concentrations in a controlled driving experiment. Researchers took blood samples immediately after participants used cannabis and a few hours later.

According to this report, THC concentrations were at their peak shortly after cannabis ingestion. Even a few hours later, blood samples could only detect minute traces of THC.

Other reports suggest THC concentrations could reach up to 100 ng/mL in a blood plasma sample three minutes after inhaling cannabis. However, these concentrations often go down to the single digits approximately one hour after smoking.

Although blood samples may find THC hours or days after cannabis use, they probably can’t detect metabolites as far back as urine samples. Many studies examining cannabis urine tests suggest these samples can give positive readings weeks after ingestion.


Does Cannabis Use Frequency Affect THC Blood Test Results? Does How Often I Smoke Affect THC Blood Test Results?


No matter what test doctors use, dozens of secondary factors could affect a person’s THC readings. Arguably, the most influential factor in any cannabis screening is drug use frequency.

THC concentrations seem to linger longer in heavy users, even in blood samples. Research out of Germany found that chronic cannabis users had higher concentrations of THC in their blood over a two-day trial period.

So, if people use cannabis more than twice per week, traces of THC will likely remain in blood samples days or weeks after use. Check out our THC calculator and see how frequency of cannabis consumption will impact the results of a drug test.


Why Would Police Ever Use Marijuana Blood Tests?


While marijuana blood tests might give a more accurate reading of current intoxication, they aren’t the most practical tests to administer. Arguably, the reason urine tests are standard in police units is that they’re easier to collect.

However, there are some cases where police may feel a blood test is warranted. Typically, authorities will request cannabis blood screenings if a driver was involved in a severe accident. The theory is that these blood tests will give a better read on the driver’s current state of intoxication.

When scientists want an accurate assessment of the active THC in a patient’s bloodstream, they will likely use a cannabis blood test. Until researchers discover a more convenient way to administer these tests, however, it’s unlikely blood samples will become the norm.


So, Is A Blood Test Best For THC Detection?


Blood tests are a valid form of cannabis screening. In fact, according to the latest data, blood tests may give the most accurate picture of a person’s THC intoxication. Some studies have also found that blood serum tests measuring between 7 – 10 ng/ml could legitimately be considered DUI.

However, there are many complexities surrounding cannabis blood tests. For starters, it isn’t easy to collect these samples on the road or in a work environment. Also, since blood tests only seem to be accurate about one hour after taking cannabis, they have a short window of opportunity.

Despite these considerations, that doesn’t mean officers or employers can’t legally request cannabis blood samples. Also, blood tests could reveal THC concentrations even after a few days of abstinence. Like other drug tests, a person’s genetics, frequency of cannabis use, and age may influence THC absorption.


Concerned About Cannabis DUI? reepher Could Help!


Considering most states have no minimum THC threshold for a DUI conviction, cannabis consumers face serious risks if they drive with the slightest trace of THC in their system. With few exceptions, police can charge a driver with a marijuana DUI no matter how little THC is in their test if their driving behavior suggests or implies intoxication. The penalties drivers will face for a cannabis DUI conviction are severe and not to be taken lightly!

If you’re a cannabis consumer concerned about potential DUI charges please check out what a reepher membership has to offer.



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