Fentanyl is a prescription opioid most-often used to treat patients after surgery. However, in recent years, it’s become one of the most common opioids on the street. Thanks to relatively simple manufacture, fentanyl and its close analogues are found in counterfeit pills like pain pills and Xanax. That ready availability means that chances are high that anyone who abuses illicit drugs will eventually try fentanyl. However, as an opioid, it will also stay in your system for some time.
Of course, being caught in a drug test is far from your biggest worry with fentanyl. At over 50 times stronger than heroin, it’s incredibly easy to risk overdose and death. In fact, Fentanyl was present in 90% of all opioid overdoses resulting in death. Fentanyl is dangerous, difficult to dose properly, and extremely strong. If you or a loved one is using, a drug test is the last of your problems.
At the same time, it may be important to understand how Fentanyl will show up on a blood test. Whether you want to know what your results will be, you’re planning to go to rehab and you need a clean test to go, or you’re just curious, this guide will help.
How Long Does Fentanyl Stay in Your System?
Fentanyl normally stays in your system for up to 3 days for a standard urine or saliva test. However, actual duration of detection will depend on factors like your metabolism, gender, weight, age, the dose you took, how many times you’ve taken the drug, etc.
In reality, you normally see a variation of “positive” results following fentanyl use in a range of days:
- Saliva – 0-7 days
- Urine – 2-4 days
- Blood – Up to 4 days, as little as a few hours
- Hair – 3 months
This means that a heavy user might show positive results over a period of much longer than someone who has used fentanyl once. Or, for example, if you had a fentanyl prescription and had to use daily for pain management, taking fentanyl illicitly shortly after might mean that it shows up in your system for longer.
However, these factors are complicated, which means you might see dramatically different results from one use to the next.
What Affects How Long Fentanyl Stays in Your Body?
Fentanyl is an opioid drug, which normally enters the body via the bloodstream, via the skin (a fentanyl patch), or orally. In each case, you’ll get different results and a different elimination period. Other things that will impact how long fentanyl stays in your body include your metabolism, weight, age, etc.
- Absorption Method – Fentanyl has a half life of 10 minutes to 4 hours, depending on how it is taken. Here, fentanyl taken orally is absorbed faster. Injected fentanyl will last much longer.
- Metabolism – Different people have different metabolisms. Men and boys under the age of 25 will normally eliminate fentanyl the fastest. The older you are, the slower your metabolism gets.
- Body Composition – Body fat stores opioids for longer, increasing the chances of fentanyl showing up on a drug test for longer. Individuals with higher muscle-mass ratios will therefore show positive results for drug tests for less time.
- Health – Healthy organs process and eliminate drugs more quickly. The longer you’ve been using or the more damaged your kidneys are, the more likely it is you’ll show a positive drug test for longer.
- Duration of Use – The more and the more often you use, the more likely it is you’ll show up positive on a drug test, even after the normal range.
These factors can be difficult to predict without an individual metabolism test. However, most people can rely on the general ballpark calculations listed above.
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Fentanyl Half Life
Half-life is the calculation used to check how quickly most people process a drug and eliminate it from their system. In this case, it specifically refers to the set metabolization rate of a drug, minus other factors.
For example, fentanyl has a half-life of about 90 minutes. This means that it takes 90 minutes for the amount of opioid you took to halve in your system. That rate continues at the same pace until the drug is no longer in your system. In addition, if you take more fentanyl during that period, it stacks on top of the other fentanyl, and elimination continues at the same rate.
- 90 minutes to ½
- 3 hours to ¼
- 6 hours to 1/8
- 12 hours to 1/16
- 24 hours to 1/32
- 48 hours to 1/64
- 96 hours to 1/120
Half life becomes complicated when you take more doses. For example:
- 90 minutes to ½
- 3 hours to ¼ – Take a new dose
- 90 minutes to the new half dose (1 + ¼ or 5/8ths)
- 3 hours to 5/16
So, if you keep taking more doses, the total amount of the drug will stay in your system for longer, because the rate of metabolization remains the same. This can greatly complicate calculations for a blood test.
In addition, half-life ranges are “the norm” or expected range. Your own metabolism may be slightly faster or slower.
Half life is used to predict how often you use, when you last used, and in what quantities you used. However, many drug tests aren’t that sophisticated. Many offer simple yes/no indicators. However, if your drug test is being sent to a lab for analysis, for example, if you disagreed with the original result and asked for a retest, you might get those detailed results back.
Why Does Fentanyl Take So Long to Leave Your System?
Fentanyl is one of the strongest opioids on the market. On the equianalgesic table, a 0.1mg dose of fentanyl compares to a 10mg dose of heroin. That’s why a dose of fentanyl can take days to leave your system and heroin can be eliminated within hours.
However, most standard drug tests (urine and saliva) won’t detect drug usage over about 4 days. If you’re unlucky or you’ve been using very heavily, a saliva test might show positive for up to a week. However, both are much more likely to cap off at about days.
At the same time, if your employer, school, or doctor choose to do a hair or nail sample, you’ll show signs of having used fentanyl for over 3 months. Still, those tests are expensive, meaning they are almost never done. And, they’re not checking for the drug itself. Instead, they’re looking for traces that it was there, such as metabolites, or substances that fentanyl is broken down into.
If you’re worried about a drug test, it’s probably a good sign to get help. Fentanyl is dangerous, too strong to dose properly, and can easily result in addiction, overdose, and even death. At the same time, there is help. If your employer is using drug tests, you can probably go to HR before the test to request help. In fact, as long as your employer doesn’t have a specific policy against it and you haven’t used at work, your employer’s insurance will be legally required to help you with rehab. In addition, many workplaces offer assistance programs as well. That also holds true for colleges and universities, which are increasingly offering preventive care and aftercare to help students get and stay clean.