How Long Does it Take to get below 50 ng/ml in a Urine Test?

Daniel Miller avatar
Daniel Miller

Last updated on May 31, 2023

Broadly speaking, it would take about 7 days to get below 50ng/ml on a urine drug test for marijuana if you smoked just one joint.

For today’s article, we’ll be talking about how long does it take to get below 50 ng/mL in your urine for a drug test for marijuana, what affects the speed of this detoxification, and how to hasten up this process so that you may pass a scheduled drug test with flying colors!

What Does 50 ng/ml Mean

I’m sure you’re quite familiar with how weed is metabolized in your body, but just in case you need a little refreshing, let’s recap the chemistry, shall we?

Marijuana’s main active component is delta-9-THC (THC). In our body, it is metabolized into several metabolites, THC-COOH (THC) being one of them.

Urine drug tests check for the concentration of THC-COOH in the urine. If the concentration of THC-COOH is above 50ng/ml, you will test positive for marijuana and fail the test.

For a Qualitative Immunoassay (IA) urine drug test, 50ng/ml is the usual cut-off level for pre-employment THC tests.

In some cases, this cut-off can be as high as 100 ng/ml and as low as 15 ng/ml, which is the case in a Confirmatory GC/MS urine drug test.

Changing the cut-off indicates that either the test method or its sensitivity has changed.

For instance, for detecting extended marijuana use, detection periods of more than 30 days are even possible in certain individuals if the 20 ng/mL cutoff value is used.

But remember one thing: negative results do not imply that a urine sample is completely free of drugs.

It may still reveal some level of a substance’s concentration in the urine, but below the cut-off level designated by the test.

How Long Does THC Stay in Your System

One joint can stay in your system for up to 18 days if you’re a heavy user. But to answer this question more precisely, there are several factors to consider.

Let’s look at each one individually.


Interestingly, women tend to metabolize THC at somewhat slower rates than men, mainly because of higher levels of body fat.

Since THC is stored in body fat, women store more THC, which is then gradually released over a longer period into their bloodstream and excreted through urine.

Frequency of Use

This is the most important factor to consider.

For first-time consumers, THC typically remains in their systems for about 3 days.

For those taking weed at least 3 to 4 times a week, their detection window is closer to 7 days after the last usage.

But for daily users, cannabinoids can be detectable for as long as 30 days, and in some cases, even more.

The potency of Strain and Your Tolerance

Another factor to remember is that different strains of marijuana have different concentrations of THC.

For example, kief takes longer to metabolize as opposed to cannabis with lower levels.

So basically, the stronger the weed, the longer it will take to be broken down and excreted by your body.

Mode of Consumption

The form of cannabis consumption also affects how long it stays in the body.

For example, smoking will get you high within minutes, whereas edibles take longer to be metabolized and kick in.

Bottom line: cannabis is excreted faster when smoked or vaped, but if consumed orally, it will linger in your system for a bit longer.

Lung Capacity

When smoking or vaping weed, how much is inhaled and how long do you hold your breath after every puff also determines how much THC will enter and stay in your system.

Body Fat or Body Mass Index (BMI)

THC is a fat-soluble chemical, which binds to and is stored in body fat. Unfortunately, this makes it even harder to get rid of it.

This makes your weight or BMI important in determining the time weed takes to leave your system; a higher percentage of body fat implies a longer time to metabolize cannabis.


The faster your metabolism and the lower your body fat, the faster marijuana will be metabolized and excreted from your body.

But this having said, metabolism is significantly influenced by age, exercise, and different health conditions.


Conditions that can increase the breakdown of fats, such as food deprivation, stress, exercise, and weight loss, can lead to the increased release of stored cannabinoids from adipose (fat) tissues.


And finally, dehydration increases the amount of THC in your body.

Even though flushing large amounts of water into your system doesn’t guarantee that you’ll pass a drug test, it will greatly dilute the level of THC in urine and make its removal faster.

How Long Does It Take to Get below 50 ng/ml?

To fully understand this concept, you’ll need to make friends with a new term: half-life. Half-life means the time it takes for half of the THC in your body to be excreted.

Let me present to you some scientific stats.

According to a study, the excretion half-life after the first five days of weed intake was around 1.3 days (27 hours) for infrequent users.

A half-life of 1.4 days (26 hours) was determined for frequent users, and some even reported half-lives of up to 10.3 days.

According to another study, if there is 27 mg of THC in a joint, THC-COOH in a smoker’s urine would be peaking at 180 ng/mL after 4 hours.

THC’s half-life was seen to vary from 1.4 days to 4 days for occasional smokers, and for frequent smokers, it may increase up to 7 days.

It’s obvious that half-lives would be longer for heavy users since the body will need more time to remove all the THC from your system actively.

It also means that smoking one joint consisting of 1g of 20% THC weed – will take nearly 7 days to get below the 50ng/ml threshold.

Now hold up: these calculations are just approximations, as I’ve mentioned the list of factors that influence them. But for generalization, these are the best numbers we have.

To make things easier and for a little more accuracy, you can use the calculator to predict the somewhat precise time THC will be excreted from your system.

How Can You Get Weed Out of Your System Faster

If you don’t have enough time and need to detox urgently, here are a few tips you can try to boost the excretion of weed from your system.

Now you know how drug tests use designated cut-off values to detect weed in urine, and how you can modify factors in your control, and also use some simple tips and tricks to help your body flush out THC from your system.

Good luck with your next urine test; you’re bound to pass now!

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