How Long Does Weed Stay in Your Blood?

Blood tests for marijuana use are frequently used by insurance agencies when determining your monthly contributions. Although one could argue that smoking the odd joint is hardly dangerous, it is classified as an illegal drug. Marijuana, as with cigarettes also contains carcinogens and may contribute to oral, pharynx, oesophageal and lung cancer.

If you want to avoid being penalised on your premiums for being a regular marijuana user, you’ll need to know the facts before you give a blood sample. And you’ll want to know how long weed stays in your blood to know what it will take before your test will return a clean result.

How marijuana affects your system

How long does weed stay in your blood

Both THC and its metabolites can be detected in your blood.

But before that, you need to understand the effect of weed on your system. Within minutes of lighting up, the active compound in the marijuana enters your blood system. It’s called THC and it is this compound that gives you a high. It’s quickly absorbed by your blood which carries it to your liver.

The liver is responsible for removing toxins from the blood. About 1450 millilitres of blood circulates through the liver every minute. Once in the liver, the THC is broken down into separate substances called metabolites. When your blood is tested, it is not screened for only THC, but often certain metabolites of it as well (or instead).

The problem with this metabolite is that it’s not removed from the body very quickly. Because it’s hydrophobic, it cannot be diluted with water. This is why drinking a lot of water will not help to clear evidence of marijuana use from your system before a urine test. Instead, the metabolite is stored in fatty tissues within your body. This includes major organs such as the heart, lungs and kidneys, and the liver itself. It’s also stored in body fat. Over time, the amount of the metabolite in your system increases with frequent use.

Small amounts of THC COOH are released from their fatty tissue deposits over a period of time. Eventually they are released back into your system where they are finally flushed out in your urine and faeces. The time it takes for your body to be completely free of THC COOH depends on a number of factors.

Factors that influence how long marijuana remains detectable

First of all there are three general factors that influence the amount of metabolites that accumulate in your system over time.

  • Dosage: How much marijuana you smoke and how potent it is will alter the amount of metabolites in your system. If you smoke small amounts, but the concentration of THC is high, this would be the same as smoking larger amounts of a lower concentration.
  • Acute or Chronic Usage: How often you use weed and how long you’ve been smoking for need to be carefully considered. An acute user may smoke regularly but over a short period of time. A chronic user is someone who has been smoking marijuana for many years. The longer you have been using the drug, the more likely you are to have high levels of THC in your system.
  • Ingestion: Smokers tend to have less THC in their systems within a few hours of lighting up. But it takes the body much longer to process marijuana that has been consumed in the form of edibles.

These factors are the same for all marijuana users. The higher the concentration of THC in your weed, along with how often and for how long you’ve been using, will determine how much of the metabolite has built up in your system, and thus how long / much effort it will take to clean up for a blood test, spit test and piss test (hair being slightly different).

There are other factors that vary between individuals. These may hold the key to determining a detox programme that can help you clear your system.

  • Metabolic rate: Some people have a faster metabolic rate and their bodies can process toxins such as THC COOH much faster.
  • Body fat ratio: Because the metabolite is stored in fatty deposits, people with a high percentage of body fat will store more than others.
  • Other medications and supplements: If you’re taking other prescribed medications, drugs or a supplement; this may slow the rate at which toxins are flushed from the system.
  • Lifestyle: Eating correctly, exercising, avoiding stress and getting sufficient sleep will help your body function better. And this means it will be able to eliminate toxins faster.

How blood tests measure THC

Bleeding finger

When your blood sample is screened, it is tested for the levels of THC COOH. The result is expressed in nanograms per millilitre (ng/ml). For most tests the minimum amount you can have in your blood and still test negative is 20 – 50ng/ml.

While THC levels peak in the blood within nine minutes of lighting up, after a few hours they drop to about 60%. Most users will test negative after about three to 5 days, similar to the saliva test, and way faster than with hair or urine. Some people think that regular users won’t test negative because they’re used to the THC and it leaves their body faster. But this is a myth—the opposite is true.

Of course, if you can delay the test, you’ll have more time for your body to process and eliminate the tell-tale metabolite from your system naturally. If you don’t have the luxury of time you can look at ways to speed up your metabolism.

Obviously you should abstain from use until your test. But you can also do more exercise, drink plenty of water and eat healthy foods. You could even visit a sauna as sweating helps to remove toxins from the body. All of this will help, but it’s not a miracle cure and it will still take a little while to clear your blood if you’re a heavy user.

Being tested for marijuana if you’re looking for insurance doesn’t seem fair. But it is the law and if you are determined to escape inflated premiums, you can take steps to ensure a negative test result.

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