A marijuana blood test is markedly different from the more common urine test that employers prefer.
In urinalysis, a test will show THC metabolites that have been in the body for quite some time. It can detect usage from 5-30 days ago.
A blood test for marijuana on the other hand only detects active THC in the blood.
But since THC levels in the blood peak then rapidly decline in a matter of hours, a blood test can only show usage from a few minutes to a few hours ago.
At most, and this is usually just for heavy users, it can only detect usage from 24-48 hours ago.
How Marijuana Blood Testing Works
When you inhale marijuana, it gets to your blood stream much faster than eating a weed-based edible.
The smoke goes to your lungs where it enters the blood stream via alveoli – tiny air sacs that facilitate respiration.
Within 5 to 10 minutes of inhaling marijuana, the amount of THC in your blood could shoot up as high as 100 ng/mL. That’s high.
But the decline is just as fast. Within 2-4 hours, the amount of THC detectable in your blood plasma descends to the single digits.
Ingesting weed on the other hand drastically reduces the number of psychedelic cannabinoids that reach your blood. Only 10-20% of THC and other cannabinoids reach the blood stream. In smoking, up to 80% of cannabinoids get into the blood.
The lower level of THC in blood when you eat a weed snack is balanced out by how long the THC sticks around. THC can still be detected in your blood for 6-10 hours after ingestion.
Regardless of how weed enters your system, it stays for a much lesser time in your blood compared to your urine or even hair. A hair follicle drug test can detect THC for up to 90 days after consumption.
A blood test can detect the much lower concentration of THC in blood compared to a urinalysis. In many urine tests, the cutoff level is 50 ng/mL, below which you pass the test.
In a blood test, any amount of THC – even as little as 1ng/mL – can be detected.
Different labs use different blood test methods. Some measure the amount of THC in your blood plasma or serum. Others, especially those used by law enforcement, measure the THC level in whole blood.
It’s interesting to note that serum holds twice as much THC as your whole blood. If you have a concentration of 2 ng/mL in a whole blood test, it will be around 4 ng/mL in a serum test.
Situations Where Blood Testing is Common
Marijuana blood testing is not common with employers.
They do not like it, for several obvious reasons. One, it is more expensive than a simple urine test. Two, it cannot indicate long term use. Remember that blood keeps THC for just a few hours while urine can keep it for up to 30 days.
But that doesn’t mean that a current or potential employer will not demand a blood test for THC.
Blood testing for weed is more common in law enforcement.
Most people suspected of driving while high will get a blood test to determine how impaired they are. However, such testing has raised a lot of questions.
In a study by the AAA, it was found that using THC blood levels to determine impairment is highly unscientific. People metabolize THC differently. One person might inhale just a little but become too impaired to drive while a chronic user might inhale a lot of it and still drive safely.
So the minimum THC blood levels set by several states including Washington and Colorado are arbitrary and unsupported by any scientific research or evidence.
A blood test could also be requested if you are in drug rehabilitation or it could be court-ordered.
Note: A blood test can detect TCH as well as the metabolite TCH-COOH. This is the same metabolite detected in a urinalysis. But in blood testing, TCH-COOH levels are not taken into consideration when determining an individual’s state of impairment. Only THC concentration matters.
How to Pass A Blood Drug Test
The best THC detox is simply waiting a few days for the THC metabolites to clear.
If you are getting a urine test, 7-30 days is enough to rid your system.
If you are getting a hair follicle drug test, 90 days is the magic number.
In a blood test, though, you’ll need up to 7 days, depending on your level of usage.
If you need to detox your blood fast, there are a few ways you can hurry the process along. Even if you have a week to detox before a blood test, I still recommend you take these steps as an extra precaution. Remember that a blood test can detect as little as 1 ng/mL of THC in blood, so you don’t want to take any risks especially if you are the longtime user.
From the blood, cannabinoids travel to the brain where they create a ‘high.’ Inhaling will often create a faster and stronger but shorter high compared to ingesting marijuana. But in both cases, the THC doesn’t stay in the blood for very long.
Single-use users (one or two tokes/hits) can test clean before 24 hours are up. Just make sure you stop using weed immediately you learn you are getting a test. It’s also not a good idea to stick around in a room where others are inhaling weed. The second-hand smoke is a risk.
For heavy/regular users, there is a chance that THC could still be detected in your blood well after 48 hours. So it’s important to take extra steps to speed up the process.
Masking Doesn’t Work For a Blood Test – Detoxing In Your Only Answer
Urine tests for marijuana have become easier to beat in recent years, because there is a myriad of ways you can ensure a negative test result.
There are detoxing products that promise to get rid of THC from your system.
Other products work by masking the presence of THC in your system.
The options in a blood test are not as many. The only way to make sure you test clean is to be clean. There is no way you are going to dilute your blood to the point where no THC can be detected. There is also no option of submitting a fake blood sample as is the case with synthetic urine samples.
So here are some of the best ways you can achieve a fast THC detox and get a clean blood test.
If you have time before the test, I recommend going to a private lab to get your blood tested to ascertain that you are clean.
You should stop using weed as soon as you learn about the drug test. This will give your system time to begin detoxing. As I mentioned earlier, it would also be a good idea also to avoid areas where other people are smoking.
The ideal abstinence period before the test will depend on various factors including how heavy of a user you are and the form in which you took weed.
For occasional users, 1 to 3 days are enough to rid the body of the cannabinoids. Chronic and heavy users can abstain it for at least a week. For full assurance, abstain for two weeks. This is because THC stored in your fat cells could be reabsorbed back into the blood. So you need time to get rid of all the THC metabolites hiding in the fat cells.
For inhalation, THC from the weed dissipates much quicker, usually within a few hours. If you ate an edible, THC could stick around for much longer, and you’ll need to abstain for longer. Be careful not to eat another pot cookie by accident.
2. Use a detox product
If you have a window shorter than two weeks, don’t rely on just abstaining. You’ll need to make sure that the THC is completely out of your system.
There are several detox products mostly in the form of drinks that promise to speed up the detox process. The effectiveness of most of these products is not guaranteed, but they have worked well enough for some people.
Make sure you go for trusted brands that have been shown actually to work.
As you will find out, there aren’t any detox products specifically for blood tests. They are designed to work with both urine and blood tests.
You will also find different products with varying detox periods. Some work within three days while others require seven days to work.
If you are a heavy user and you have time, I recommend a 7-day detox product.
For quick detox and for those with no time before the test, try 3-day detox drinks.
Until the day before the test maintain a regular exercise routine.
You probably know that THC is stored in fat cells. This is why marijuana traces stay in your body far longer than for most other drugs.
You also know that exercise burns fat.
The more you exercise, the more fat cells you burn and hence, the more THC is released out of the body either in urine or stool.
Cardio is especially ideal since it burns faster than other forms of exercise.
Notice that I said ‘until the day before the test.’ If the test is on Friday, take Thursday off from working out. This is for a significant reason.
When you exercise, fat cells break down and the THC metabolites stored in them are quickly reabsorbed back into the blood.
So if you exercise right before the test, there is a higher risk you will not pass.
With a full day break, there is enough time for any reabsorbed THC to be excreted out of the body.
4. Eat healthy (fiber and vitamins)
A healthy diet helps speed up the detox process. Vitamins and other minerals play a crucial role in helping the body get rid of various toxins. Eating high-fiber food makes you go to the toilet more, which results in more THC being excreted together with the stool.
Focus especially on fruits and vegetables and avoid junk snacks and processed foods.
Don’t forget to drink plenty of water. It will not dilute your blood but will help your body detox.
5. Use fruit pectin
Eating fruit pectin is a controversial way of removing THC from the system. It’s not that it is unsafe (the risk are minimal) but there isn’t much evidence to back up its effectiveness. I wouldn’t recommend it on its own. Only use it combined with other detox strategies especially if you are a heavy user.
Pectin is a type of fiber that is added to jams and jellies. Like any other fiber, it forces your body to produce more stool and hence more THC is excreted. But it also has another more complex way of removing THC.
Pectin binds itself to bile in the intestines which reduce the amount of THC that is absorbed into the blood stream. This only applies if you ingested rather than inhaled weed.
6. Use activated charcoal
Another controversial detox method involves activated charcoal, a highly porous carbon. There is not sufficient evidence to support its effectiveness.
If you are going to use it, experts recommend taking it after eating a weed edible. This is because charcoal best absorbs THC and other drugs while they are still in the digestive tract thus preventing them from getting absorbed into the blood.
Blood Testing + Urine Combined Test
In some cases, you may be needed to undergo both urine and blood testing.
In such a situation, you’ll have to make double the effort to beat both tests. Urine testing is a bit harder to beat but still doable.
For tips on how to get weed out of your system fast, regardless of the type of test, see our guide.
My name is Jay Wilson, but my friends call me JZ. Originally from Atlanta I now live in Denver, CO where things are ‘freer’ these days. Several years ago, I put this site up for a friend who asked me to find ways to beat his upcoming hair drug test. Fast-forward to today, I’ve answered more than 1,000 questions about the hair drug test and proven ways to beat it. I am an expert in the hair test – ask me anything!