Drug tests are a common hurdle in many job application processes. Some employers also use random or targeted drug tests as a practice. For those taking a prescription drug like Flexeril, there is also the concern that it will show up on a screening and cost them a job. This is complicated because there are several types of drug tests, including hair, blood, urine, and saliva tests.

Flexeril is a muscle relaxant that’s often used to treat spasms or pain during physical therapy. It works by blocking certain nerve impulses. Its brain effects tend to prove mild, with drowsiness, dizziness, or headaches as the most common side effects. If you do take Flexeril, you might wonder how long it stays in your system. Keep reading and we’ll cover how long it stays in different parts of your system.

How Long Does Flexeril Stay in Your Urine?

The first thing you should know is that there are no hard and fast rules about how long Flexeril or any other drug stays in your urine. It’s not the same for everyone. A variety of factors affect this, including:

  • Metabolism
  • Genetics
  • Age
  • Weight
  • Frequency of use
  • Duration of use

The general rule of thumb is that Flexeril has an 18-hour half-life. An average person with average weight who took a normal dosage will typically clear the drug out of their system in about 4 days.

Of course, if you’re not average or taking higher doses, how long it lasts in urine and stays detectable in a lab test may be longer or shorter. On the high end, it might stay detectable for up to 10 days.

How Long Does Flexeril Stay in Your Hair?

The question of how long Flexeril can show up in a lab test using hair is a little more complicated. Average hair growth holds steady at about 1/2-inch per month. Drugs deposit in the hair through the follicle. That starts at about the same time as the drug enters your bloodstream. So, a lab test can pick up a drug like Flexeril very soon after you take a dose. As long as you keep taking the drug, it will keep depositing in your hair.

The time since last taken that it can show up is around 3 months. A hair test done correctly uses 1.5 inches of hair. This is measured from the root. Since hair grows at about 1/2-inch a month, it takes a little over three months before drugs won’t show up in a hair test.

How Long Does Flexeril Stay in Your Blood?

Much like your urine, how long Flexeril stays detectable is based on the 18-hour half-life of the drug. You should assume it’s still in your blood for at least 4-5 days. If you prefer to be cautious about it, assume 10 days.

While blood drug tests provide the best results, they’re not a popular choice for employers. Blood tests require a medical professional to draw the blood. Many people consider it unreasonably invasive for an employer to require you to get blood tests. It’s also expensive compared with other tests.

How Long Does Flexeril Stay in Your Saliva?

Flexeril stays in your saliva for the same amount of time as it stays in blood and urine. Unless you know you have a high or low metabolism, it’ll be 4-5 days.

While not as common as urine drug tests, saliva tests are a popular alternative because employers can conduct them on-site. The transportation and safety industry must perform drug testing for legal reasons. So, you’re more likely to face saliva drug screenings if you work in those industries.

How Long Does Flexeril Stay in Lab Tests?

Unlike many other prescriptions, Flexeril does not show up on standard lab drug tests. That goes for hair, urine, blood, and saliva. The only time it might show up is if someone asks for a screening that looks for antidepressants. Flexeril will show up on those tests.

As a general rule, you should report your Flexeril prescription at the time of the drug test. There is typically a section for it on the paperwork you always fill out. This can help you avoid problems with potential employers or anyone else who requires a drug screening. With that said, Flexeril doesn’t show up on any of the standard urine, blood, hair, or saliva tests.


  1. https://www.drugs.com/flexeril.html
  2. https://www.rxlist.com/flexeril-drug.htm
  3. https://www.healthline.com/health/beauty-skin-care/grow-hair-faster
  4. https://www.health-street.net/blog-drug-testing/hair-drug-testing-facts-and-myths/
  5. https://www.thebalancecareers.com/what-is-a-mouth-swab-drug-test-2060405

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