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If I Smoke Weed Once, Will I Fail Urine Test?

Marijuana contains THC (delta-9 tetrahydrocannabinol), a psychotropic or euphoria substance that stimulates the part of your brain and causes “high.” A drug test is not usually administered to detect the THC molecules in your urine but rather the waste products your body produces after smoking weed.

Many occasional smokers think that they will fail the drug test because they smoked marijuana once before. Could this be true? Well, it is complex than to answer right away. Therefore, read on, as we breakdown this question into smaller parts.

  1. How long does weed stay in your system?
  2. How much you need to pass a urine test
  3. How much is 50 ng/ml?
  4. THC half-life
  5. Will i pass a drug test if i smoked 1 week ago?
  6. Will I pass a drug test if I smoked weed few days ago?
  7. Can I pass a drug test the next day?
  8. Can I pass the urine test in a few hours?
  9. Will I fail urine test if I smoke weed once?
  10. Important notice

smoke weed once

How long does weed stay in your system?

Whether you smoke occasionally or you are new to cannabis, having handful information about how your body reacts to weed is essential. When you smoke weed, THC metabolizes in your body system which gets you high for a few hours as your body processes the psychoactive content.

But the end product called metabolites stores in your fat cells and organs of your body for several weeks until fully clean. Depending on your frequency of smoking, metabolism, and the amount of fat you possess in your body, the longer it takes for the metabolites to clean from your system.

How much you need to pass a urine test

A urine test is considered non-invasive and relatively accurate. Technically, weed doesn't stay in your urine, but its waste products do stay. A urine drug screen for marijuana contains immunoassays with antibodies that are made to detect THC's main metabolite 11-nor-delta-9 Carboxy-THC (THC-COOH).

The accepted cutoff level for THC-COOH in urine test is 50 ng/ml. This means that result is considered negative if you have less than 50 ng/ml, otherwise it's positive. When the initial urine screen is positive, a Gas chromatography/Mass spectrometry test will be used to verify the result at a cut off level of 15 ng/ml.

How much is 50 ng/ml?

CarboxyTetrahydrocannabinol is the most abundant metabolite that stores up in the system and ultimately the compound of interest during a urine test. According to studies, the average joint gives about 150-200 ng/ml peak concentration of THC-COOH in urine 4 hours after smoking. So, by approximate calculation, 50 ng/ml is about 1/4 or 1/3 of a joint, but it strongly depends on your cannabis potency.

THC half-life

Half-life is the time frame it takes for a substance to reduce by half its initial value. The half-life of THC is not the same as the duration at which you stay “high”.

Half-life of THC in urine is about 30 hours. This means that near every 30 hours, THC concentration in urine is reduced by half. So, having 200 ng/ml after smoking joint will give you about 100 ng/ml next day and about 50 ng/ml 2 days after smoking.

This calculation is very rough, because half-life heavily depends on many factors, such as way and frequency of marijuana use, body structure, drug potency, fluid intake, metabolism rate and so on.

Will i pass a drug test if i smoked 1 week ago?

Regardless of all information about whether you will pass a drug test or not still depends specifically on your body and the potency of marijuana. In most cases, a week is long enough to flush THC out of your body. So yes, if you smoked only once, you are very likely to pass a urine test after one week. After 2,3,4 and more weeks chances are 100%, but one week is close to 100%.

Will I pass a drug test if I smoked weed few days ago?

The short-lived effect of THC does not prevent the evidence of marijuana from lingering in your body system. For as long as the chemical exists in your body, you are at the risk of failing a drug test. If you had smoked weed a few days ago, your chance of passing is 50-50 depending on marijuana potency and your metabolism. Having few puffs will give you THC-COOH level under 50 ng/ml in 1-2 days, after one joint you can pass the test in 3-5 days.

Can I pass a drug test the next day?

The time it takes for weed to get out of the system depends on how often, how much and for how long the user has been smoking. If you don't have a history of marijuana smoking and you did just a few puffs, it's possible but not guaranteed to pass a drug test the next day. After a joint or even half of a joint, you will fail.

Can I pass the urine test in a few hours?

Surprisingly, yes. As it was said before, urine tests check for THC-COOH, not THC itself. THC-COOH is a metabolite of THC and body needs some time to metabolise THC into THC-COOH and excrete it with urine. According studies, the peak concentration of THC-COOH in urine comes about 4 hours after smoking. So, 1-2 hours may not be enough to accumulate 50 ng/ml in urine and you can pass. This is why saliva tests are used to detect recent cannabis use.

So, the main question is:

Will I fail urine test if I smoke weed once?

Several factors come to play that can improve or decrease your chances of passing a drug test. Studies have shown that occasional smokers can pass a urine test in a few days.

If you did just 1-2 puffs, the chances are that you will pass even the next day, if your strain was weak.

If you had a full joint, you would fail in the next few days. But it's impossible to say for sure how many days you need to get clean, it depends on weed potency and your metabolism.

You will pass the urine test for sure about one week after smoking weed once.

Important notice

This information is only for one smoke, not for regular users! Even if you had smoked a few weeks ago, some residue might stay in the body and impact test results.

The calculations above are rough. At the end, it all depends on weed potency and your metabolism! You should not rely on this information when preparing for passing a drug test.

To know if you are ready for a drug test you need to be able to figure out the number of metabolites in your urine. You can use the THC calculator to calculate your approximate level of THC-COOH. It also helps you to understand the test passing probability.

When your chances of passing a drug test are slim or you are not sure about result, use THC detox kits that clear THC metabolites from your system. They include high-quality detox drinks that will help dilute your urine. This detox drinks contain vitamin B and creatine that will help cover up the fact that your urine is diluted.