20 vs 50 vs 100 ng/ml - How To Pick The Best Home THC Test
Medically reviewed by Dr. Matthew Nuesse, Certified Medical & DOT Examiner
When it comes to how to pick the best THC home test, even though every test is designed for detection, there are a few nuances to consider. At Exploro, we try to suit everyone’s needs, be it for a detox, tolerance break, or even a pre-employment test.
Let’s dig into terms like “ngml”, “cutoff levels”, and “detection time”, and shed some light on this important factor of at-home THC testing. By the end of reading this article, you’ll be equipped with the knowledge to pick the best test for yourself.
In the following article, we will discuss:
- What is ng/ml?
- What are cutoff levels?
- 20 vs 50 vs 100 ng/ml - The Main Differences
- Cutoff Levels FAQ
What is ng/ml?
In a literal sense, ng/ml (or ngml) is short for nanograms per milliliter. In the case of THC urine testing, it refers to nanograms of THC-COOH metabolite (that remains in the body after use) per milliliter of sample fluid (urine).
In practical terms, the ng/ml measurement represents the sensitivity of a THC test, also known as a cutoff level. When choosing a test, to get an adequate cutoff level, you need to consider several lifestyle and THC usage factors, such as:
- Frequency and amount of use
- Body fat percentage
- Metabolism rates (exercise and dietary habits)
- Hydration habits
- Involvement of CBD hemp-based products that may also contain THC
THC Cutoff Levels Explained
A cutoff level, aka test sensitivity, is a chemical threshold above which the test will turn out positive. The lower the cutoff level, the more sensitive the test is, meaning that it can detect THC metabolites in urine in lower amounts. It’s directly related to the detection window, which marks how far back the test can detect THC use.
To put things in perspective, the lower the cutoff level, the larger the detection window is. Again, all of this depends on the metabolic factors, especially the frequency of use.
If you want to check your individual status based on these factors, we encourage you to try our THC detection calculator.
There are three main cutoff levels that home THC tests come with:
- 15 or 20 ng/ml - lowest cutoff for the largest detection window
- 50 ng/ml - standard screening test cutoff often used for official testing.
- 100 ng/ml - a high cutoff level that detects heavy use
In practical terms, for a light occasional user (1-4 times a month), the cutoff levels and detection windows would look like this:
|
Cutoff level |
Detection window |
|
100 ng/ml |
1-2 days |
|
50 ng/ml |
1-4 days |
|
20 ng/ml |
3-7 days |
*Again, these detection windows vary based on factors mentioned above. The table doesn’t apply to heavy users.
20 vs 50 vs 100 ng/ml - The Main Differences
Now that we covered what cutoff levels and detection windows are, to pick the best THC home test for your situation, let’s see what the standard three levels represent in practical terms, and who they are best for.
20 ng/ml - The Confirmatory Cutoff
With the strictest cutoff level (and the largest detection window), this type of test has several purposes. It is designed to catch light or older THC use. Additionally, a 15 or 20 ng/ml cutoff is the confirmatory cutoff level used in laboratories. Here’s a list of scenarios where a 20 ng/ml cutoff matters the most:
- Court or legal monitoring
- Probation programs
- Checking whether you’re fully clean before a confirmatory test
- Situations in which any recent use matters
50 ng/ml - Standard Screening Cutoff
The 50 ng/ml cutoff level is the most common when it comes to THC testing, and is designed to detect meaningful recent use. It’s used as a screening test, and it has a balanced sensitivity and detection window. It is the most common home THC test cutoff level as well. Here are a few scenarios where a 50 ng/ml cutoff is most likely to be seen:
- DOT drug testing
- Employment and pre-employment drug screening
- Detection of recent use
- People who have an upcoming surgical procedure and need to abstain from use
- People who want to know if they would pass a normal job drug test
100 ng/ml - Where Detox Starts for Heavy Users
This is the cutoff level with the shortest detection window. It is designed to detect very recent or heavy use of THC. The 100 ng/ml cutoff THC test has a detection window of just 1 to 2 days for occasional users. Here are a few scenarios where a 100 ng/ml cutoff is most useful:
- Starting a detox after a prolonged and/or heavier use
- Self-checks after use of high-THC products (edibles included)
- Situations where only high THC metabolite levels are important
Cutoff Levels FAQ
1. Is 20 ng/ml more sensitive than 50 ng/ml?
Yes, it is. A 20 ng/ml cutoff level is way more sensitive than 50 ng/ml. It is designed to detect light THC use, or even older use. A level this sensitive is most commonly used for confirmatory tests, or in situations where you want to know if you’re “clean”.
2. How long does it take to get under 50 nanograms?
The only real answer is - it depends. Here’s an approximation depending on the usage (results may vary on factors like metabolism and lifestyle):
- For one-time or occasional users, it takes about 1 to 4 days to get under 50 ng/ml
- For light weekly users (1 to 2 times), it takes about 7 to 30 days to get under 50 ng/ml
- For moderate users (3 to 4 times a week), it takes about 7 to 14 days to get under 50 ng/ml
- For heavy/daily users, it can take anywhere from 4 weeks to up to three months to get under 50 ng/ml
*These approximations heavily rely on using habits, body fat, and lifestyle
If you want to take a deeper look at how bodyfat affects detection windows, take a look at Dr. Matthew Nusse’s experience with THC testing:
3. What is the detection time for 100 ng mL?
Detection time is essentially “how soon can THC be detected after use.” Now, being that 100 ng/ml is the least sensitive test, after a heavy THC dose, we can say that:
- 2 to 6 hours - THC metabolites start appearing
- 6 to 12 hours - the metabolites may cross the 100 ng/ml threshold
- 12 to 24 hours - the detection window is most reliable
4. What is a positive THC level?
In most cases (e.g., DOT, employment), a result above 50 ng/ml is considered a positive THC result. If this happens on a screening test, the medical examiner will require a confirmatory test that’s done in a laboratory at a lower cutoff level (15 or 20 ng/ml).
20 vs 50 vs 100 ng/ml - Now You Know The Difference
Now you know how to approach THC testing and choose the right THC home test. If you’re going into a job hunt or need to perform a drug test at work, you will most likely need a 50 ng/ml home THC test, since that is the level they screen at.
But, if you’re looking to detox after prolonged use or want to do a self-check after using some strong THC products, the 3-level home THC test is ideal. It tests at 20, 50, and 100 ng/ml cutoffs.
All in all, you’re armed with knowledge on how to pick, and you don’t have to wonder what “cutoffs” and “detection windows” are.
Resources:
- https://pubmed.ncbi.nlm.nih.gov/8926739/
- https://www.ecfr.gov/current/title-49/subtitle-A/part-40/subpart-F/section-40.85
- https://www.thermofisher.com/rs/en/home/clinical/diagnostic-testing/clinical-chemistry-drug-toxicology-testing/drugs-abuse-testing/drug-testing-overview/samhsa.html
- https://ntcrc.org/wp-content/uploads/2020/06/DCRVolume5.1-2_The_Marijuana_Detection_Window.pdf
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