Phentermine is a central nervous system stimulant that is FDA-approved as a weight loss medication.[1] It is only intended for short-term use, as it can be habit-forming and addictive. Because of the risk of abuse, phentermine is a controlled substance.
While phentermine helps treat obesity, some people misuse it to experience mind-altering effects. It can cause a rush of euphoria, increased energy, and fast heart rate or high blood pressure.
If you or a loved one abuses phentermine, you might be wondering how long it stays in your system. The half-life of phentermine is about 20 hours.[2] It can take up to 4 days for phentermine to leave your system.
Drug tests can detect the metabolites of phentermine for varying amounts of time. For example, drug screens can find phentermine in urine for 1 to 4 days after your last dose.
In this article, you will learn:
- What effects does phentermine cause
- What is phentermine’s half-life
- How long can drug tests find phentermine in your system
What are the Effects of Phentermine?
Phentermine is a stimulant, which means it speeds up activity in your brain. You might experience increased energy, a fast heart rate, and even anxiety. If you are abusing phentermine, you could feel a rush of euphoria, however, taking too much can result in an overdose.
The side effects of phentermine include:[3]
- Headaches
- Dizziness
- Trouble sleeping
- An inability to feel sensations
- Trouble concentrating or remembering
- Excessive tiredness
- Dry mouth or increased thirst
- Decreased ability to taste food
- Nausea, diarrhea, and constipation
- Heartburn
- Painful menstrual periods
- Hair loss
If you experience symptoms like a racing or pounding heart, fast or shallow breathing, or a sudden decrease in vision, contact emergency medical services immediately. You could be having a bad reaction or an overdose from taking too much phentermine at once.
What is the Half-Life of Phentermine?
To understand how long phentermine stays in your system, you need to know what a drug’s half-life is. The half-life explains how long half of a dose of a drug stays in your system. It can take 4 to 5 half-lives for your body to eliminate a substance.
The half-life of phentermine is approximately 20 hours.[2] This means it stays in your system for up to 4 days.
It is important to note that several factors can play a role in how long phentermine stays in your body. Some of these factors include:
- The speed of your metabolism
- Age and overall health
- The dose and frequency at which you take phentermine
- Body mass index (BMI) and weight
- The function of your liver and kidneys
- Hydration and nutrition levels over time
How Long Can Drug Tests Detect Phentermine?
Phentermine will show up on drug tests that detect amphetamines. The most common drug screens are 5-panel drug tests, which look for opioids, marijuana, amphetamines, cocaine, and phencyclidine (PHP). In other words, a standard drug test will show up positive if you have phentermine in your system.
The amount of time that phentermine is detectable depends on what type of drug test is being used. There are urine, blood, hair, and saliva drug tests.
Urine
Urine tests are the most commonly used drug tests because they are relatively cheap and minimally invasive. You might be asked to complete a urine drug test before being offered employment, during a drug rehab program, or in a probation office.
Phentermine is detected in urine for 1 to 4 days after your last dose. If you use high doses of phentermine long-term, you are more likely to test positive longer.
Blood
Blood tests are not used as commonly as urine tests because they are invasive. A blood draw is required to perform one. That said, they might be used in a hospital setting when your blood is being taken for other types of testing.
Blood tests can detect phentermine in your system for 19-24 hours after your last dose.
Saliva
Saliva tests are not used as frequently as urine tests because they tend to offer a shorter window of detection. This is because drugs pass through your saliva before they even reach your urine. That said, law enforcement officers often use saliva tests during field sobriety tests because they are convenient.
Saliva tests can detect phentermine in your system for 48 hours after your last dose.
Hair
Hair tests are not used often for a couple of reasons. First, they are expensive to send off to the lab. On top of that, they offer unreliable results because they can discriminate based on things like hair color.
Despite this, some high-security clearance jobs use hair testing because it offers a long window of detection. Hair tests can find any substance in your system for up to 90 days after your last dose.
Find Help for Phentermine Abuse and Addiction
If you or a loved one suffers from phentermine addiction, it’s time to seek professional help. Drug rehab programs like the Mandala Healing Center can offer the tools and support you need to recover. We offer services like medical detox, evidence-based behavioral therapies, and relapse prevention planning.
Contact the Mandala Healing Center today to learn more about our highly-rated phentermine addiction treatment program.
References:
- The Food and Drug Administration (FDA): Phentermine Label
- The National Library of Medicine (NLM): Topiramate and Phentermine
- Medline Plus: Phentermine and Topiramate