Will Phentermine Show on a Drug Test?

“Will phentermine show on a drug test?” is a vital question that many may ask but never fully receive an answer to. Allow us to provide this to you. The answer to this question may surprise you: yes, phentermine will show up on a drug test, but not as you would think. Drug tests do not test for phentermine, but they will likely give you a false positive result for amphetamines. 

What Is Phentermine?

Phentermine was initially approved for medical use in 1959. It was meant to act as an appetite suppressant that, alongside proper diet and regular exercise, would assist those struggling with obesity. It was meant for those seeking weight loss, especially for those with a history of high blood pressure, high cholesterol, or diabetes (the reasoning for this is currently unknown). 

Much like amphetamines, the substance acts on the central nervous system by stimulating the part of the brain responsible for an increase in three essential neurotransmitters: dopamine, serotonin, and norepinephrine. These neurochemicals can suppress appetite and lead to a feeling of “being full.” However, they can also easily be abused in the wrong hands, hence phentermine’s current state as a controlled substance.

Although it does not have the same energetic or euphoric effects as those who take or abuse amphetamines, phentermine remains a Schedule IV controlled substance and is not known to be habit-forming.  It belongs to a class of drugs called “anorectics,” or weight loss supplements that require a prescription. They are typically only used in extreme weight loss cases.

So, will phentermine show on a drug test? Yes. It is meant to be used for a short period of time and has a potent half-life (i.e., how long the drug remains in the system). A half-life implies that when in your system on day one, it is 100 percent detectable, but by the fourth day, only 25 percent remains. Its stimulating nature can still be, and still is, abused. If taking phentermine, you should tell your doctor immediately if you experience any of the following side effects:

• Headache
• Dizziness
• Numbness
• Dry mouth
• Nausea
• Diarrhea
• Constipation
• Severe heartburn
• Painful or frequent urination
• Fever, sore cough, or congestion

These are a select few side effects that do not require immediate intervention. If you experience a sudden decrease in vision, a racing heartbeat, eye pain or redness, shallow breathing, severe neck or side pain, rashes, and hives, do seek immediate medical attention.

Worried About What a Drug Test Reveals About Your Phentermine Use?

Most people reading this page are not worried about phentermine showing up on a drug test because they filled a legitimate prescription and forgot to mention it to their employer. They are worried because the way they are using it has drifted from what was originally prescribed, and a positive result would raise questions they are not ready to answer.

That is a more common situation than most people admit out loud.

Phentermine is a Schedule IV controlled substance, which means it has recognized medical uses but also a real potential for dependency and misuse. It is prescribed as a short-term weight loss aid, typically for a few weeks at a time. But the appetite suppression, the energy it produces, and the mood effects that come with it make it easy to want to keep using it beyond the prescription window. Some people obtain it outside of a doctor’s relationship. Some people increase their dose. Some people find that stopping it, even temporarily, feels harder than it should.

If any of that sounds familiar, what you are dealing with is not a willpower problem. It is how stimulant dependency works.

Some signs that phentermine use has moved into dependency territory:

• You are using more than prescribed or sourcing it outside of a doctor’s supervision
• You have tried to stop or cut back and found it genuinely difficult
• You feel flat, fatigued, or low without it, beyond what you would expect from normal hunger
• Your use is affecting your sleep, heart rate, mood, or anxiety levels
• You are spending time managing your supply, hiding your use, or worrying about drug tests

None of these are moral failures. They are the predictable effects of a stimulant that the body adapts to over time.

The reason you are searching for how to flush phentermine out of your system is worth sitting with for a moment. If the answer you are hoping for is a way to keep using without consequences, that is understandable. It is also a sign that the relationship with the medication has become something worth taking an honest look at.

What Phentermine Dependency Treatment Actually Looks Like

Stimulant dependency, including dependency on prescription medications like phentermine, is treatable. It does not require hitting a dramatic rock bottom. It does not require having lost a job or a relationship. It requires recognizing that something has shifted and deciding you want support to shift it back.

At Muse Treatment in Los Angeles, we work with people navigating dependency on prescription stimulants as part of our broader prescription drug addiction treatment programs. That includes a confidential assessment to understand your specific situation, a medically supervised approach to stopping safely, and therapy to address what was driving the use in the first place.

The first conversation is completely private. We will not contact your employer, your doctor, or anyone else. Our admissions team is available 24 hours a day and the call carries no obligation.

If you are relying on phentermine beyond what was originally prescribed, or if the way you are using it is creating problems you are trying to manage around, our prescription drug rehab in Los Angeles can help.

How Drug Tests Work

There are several types of drug tests: urine drug testing (UDT), blood drug testing, hair follicle drug testing, breath drug testing, and sweat drug testing. Saliva and swab tests have also become increasingly used in recent years due to the inability to cheat a saliva swab test, though they prove less efficient. So, does it work? 

When asking, “Will phentermine show on a drug test?” the best answer is understanding how drug tests work. When you consume a substance, the gastrointestinal tract takes in the drug and sends it out through the rest of your body. The liver and other organs begin to break the drug down into metabolites, which, in specific quantities, can leave the body through urine. 

A drug test may detect only one type of drug at a time or test multiple types. Commonly-tested substances are amphetamines, cocaine, marijuana, benzodiazepines, PCP, alcohol, fentanyl, heroin, hydrocodone, and barbiturates, among many others, and, as you can see, phentermine does not show up on this list. However, due to its close chemical composition, it will show up as an amphetamine as a false-positive.

For simplification, let us focus on urine tests. Antibodies are cells that are added to the drug screening mechanism, where, for a positive result, the number of antibodies that attach like a parasite can detect the presence of a specific antigen or substance. During standard urine screenings, for example, any substances present in the urine specimen will cause binding sites of a particular antibody that will detect the protein conjugate for the drug. The antibody reacts by showing a revealable colored line indicating the substance is in the individual’s system.

Antibodies can look for one form of drug or many, depending on the scenario. As an example, inpatient and outpatient drug screenings test for multiple types of drugs in one’s system, as this allows detection of any illegal or unregulated consumption of an illicit or controlled substance. Though urine tests are typically the most efficient and widely used due to their accuracy, other tests also exist. An example is a hair test, which can detect drugs for up to 90 days after use (based on DNA), whereas urine tests may fluctuate based on water intake. Note: the myth of “drinking more water” before a drug screening has proven not to work.

Will Phentermine Show Up on a Standard Drug Test?

Will phentermine show up on a drug test? Yes. However, if medical documentation of the drug’s use is provided, it can be presented, and if needed, the false positive may or may not be negated. Reach out to Muse Treatment for more information on how this works. 

In the end, the short and simple answer to our question is “no,” but it will produce a false-positive confirmation for amphetamines. Though it is indicative that phentermine and amphetamines would be unequally compared, make sure that your administrator has access to any documentation of the medications you are on.

When asking will phentermine show on a drug test, It can be detected in your system via urine (about four days after the last use), oral swabs (48 hours since the previous dose), oral swabs (around 48 hours after the post-consumption), and hair follicle samples (90 days after the last dose). So, will phentermine show on a drug test? The short answer is yes; phentermine will show up as a false positive for amphetamines. If you have a prescription, bring it to the drug screening so the testing facility has records and documentation.

Factors Influencing Detection of Phentermine

Asking: “Will phentermine show on a drug test?” depends on the amount of the substance and your body’s natural metabolic rate. It can last in one’s system for around four days. Because everybody has a different metabolic rate, it can last anywhere between 4-6 days. Now, most drugs have a limit for their rate of metabolism, which will inadvertently lower the concentration of the enzymes needed for the drug screen to take place. This rarely occurs, and the effect is that metabolic rate increases with the concentration of the drug.

Phentermine also has a similar chemical composition as amphetamines, so despite the frequency of use or dosage, it will remain in your system for up to 4-6 days. Will phentermine show on a drug test? To answer this question, we must first examine what a false-positive is. This will give you some helpful information when asking whether phentermine will show on a drug test.

Phentermine and False Positives

Because it is not typically involved in a drug test, a “false-positive” result can lead to it being detected as an amphetamine due to both substances having a somewhat similar chemical composition. Remember that phentermine is still a controlled substance. So, will phentermine show on a drug test? Yes, but not in the way you would think.

During a drug screening, it will appear as a positive for amphetamines, known by many as the primary “ingredient” in ADHD medications such as Adderall. It is called a “false-positive” because drug screenings are often known to identify one type of drug with another incorrectly. However, unless you have a prescription for phentermine, you will not have much legal or ethical recourse. Your best bet is to bring all medical documentation with you when tested.

What to Do if Phentermine Shows Up on a Drug Test

First, ensure that the employer is aware of the use of phentermine. At Muse Treatment, we strive to help you understand this process. You will appear to be hiding something if you do not mention it. Justify the legitimate use of the prescription. 

Second, collect any required documentation related to your prescription before the drug test. This allows you to indicate that, in the event of a false positive, you have a) made it clear that one may result and b) the benefit of appearing honest about its usage.

This is best done through the prescription or a note from your prescribing doctor. Next, make clear to the employer that you are using the substance for a legitimate reason and that there is the possibility that it will result in a false positive. Consult the prescribing doctor about your prescription; try to obtain documentation that you are using this medication for weight loss and that it may be a resulting false positive for amphetamines. Again, having documentation assists.

By following these steps, you can effectively manage a positive drug test result for this medication, ensuring that your use of the phentermine is appropriately and accurately documented and understood by your employer or the testing authority. Honesty is vital, so be upfront. We hope you know: Will phentermine show on a drug test?

Muse Treatment’s Approach to Medication Management

You can receive information on phentermine use, as well as substance use disorder for any medication or drug, from Muse Treatment. We offer a full range of addiction treatment programs, including inpatient drug rehab and outpatient rehab, as well as specialized programs like dual diagnosis treatment for co-occurring mental health disorders. Our Los Angeles drug rehab center has an expert team that thoroughly evaluates your condition and recommends the most effective treatment plan. Our streamlined admissions process ensures that clients can begin therapy and treatment promptly because untreated addiction tends to worsen over time. 

Contact Muse Treatment at 800-426-1818 to begin your recovery journey. With our support, you can regain control of your life and health. Our compassionate clinicians offer care in an environment designed for lasting recovery. We’re committed to helping you mitigate the risks associated with false positives on drug tests and phentermine use.