How Long Does Phentermine Stay in your Urine, Blood, and Hair?

Phentermine can give a false-positive result for amphetamine in a 5-panel drug screening urinalysis. That because of the similarity of both chemical structures. The duration of time that Phentermine’s effects detected in your hair, urine, and blood can vary due to several factors.

If you want to avoid Phentermine’s false-positive test results, there are a few things you need to understand, which we will cover in this article.

Phentermine (commonly known by brand names Lomaria and Adipex P) is a medication prescribed to patients to help them lose weight by suppressing their appetite. The typical prescription is for a period of 6 weeks, however, those who observe a low-calorie diet and exercise regularly can use it up to 12 weeks.

Other prescription medications such as Ionamin, Zantryl, Fastin, and Qsymia contain phentermine as an active ingredient.

These medications are not just the most commonly prescribed dietary medications, as they are stimulants in the same way amphetamines are, they are listed as a controlled substance.

Many of the sales of these diet pills end up, therefore, being illicitly made. This also ties in with the potential of phentermine to becoming an addictive substance.

Phentermine users need to be aware of how the drug affects their bodies, as well as how long it stays in their system to prevent undesirable side effects or encountering interactions with other medications.

A commonly used SAMHSA amphetamine test can detect phentermine in urine, blood, and hair, with the 5-panel urine version being the most widely administered, while the blood and hair follicle tests are somewhat less regular.

How Long Does It Take to Feel Phentermine’s Effects?

In its function, phentermine resembles amphetamines due to its attributes of stimulation of the central nervous system, appetite suppression, and elevating blood pressure.

The medication is consumed in either a tablet form (thrice daily, before meals) or once in the morning in form of an extended-release capsule (typically with a 37.5mg dosage).

It reaches its peak concentrations in the blood in 3 to 4 hours after being absorbed through the digestive tract. By such time, the effects indicating that the drug is working become evident.

Some of Phentermine’s short-term effects might include:

  • Lessened appetite
  • Hyperactivity
  • Chest pressure or pain
  • Euphoric sensation
  • Irritability or anxiety

Phentermine is a controlled substance (listed on the Drug Enforcement Agency’s March 2008 List of Controlled Substances). Phentermine can only be legally obtained by doctor’s prescription due to its amphetamine-like effects. These include an increase in the level of dopamine, serotonin, and norepinephrine.

How Long Do the Effects of Phentermine Last in your Urine, Blood, and Hair?

Phentermine’s half-life is 20 hours. In other words, this is the time it takes the body to metabolize half of the dosage and excrete it through urine.

To be eliminated from the user’s system, it takes approximately five or six half-lives. 70% to 80% of phentermine hydrochloride (the drug’s primary active ingredient) is relieved from the body unchanged through urine, while the rest forms corresponding metabolites while undergoing N-hydroxylation and N-oxidation.

  • Urine: Using the SAMHSA 5-panel’s amphetamine test, phentermine can be detected in anywhere between 1 and 4 days. If one was to stop taking phentermine a week before a urine drug test, they can safely expect phentermine use to not be indicated on the test.
  • Blood: A blood test detects phentermine in the system for up to 24 hours.
  • Hair: The presence of phentermine can be detected through testing hair follicles for up to several months.

False Positive Test Results

A study confirmed that due to a similar makeup to amphetamines, phentermine can manifest on an MDMA test for amphetamines.

If such a test is to return a false positive based on the presence of phentermine, a secondary test is performed that confirms that there is phentermine in one’s system, rather than amphetamines or methamphetamines.

In either case, if a test is being conducted, it is always best to disclose a phentermine prescription before the test is conducted in order to have a clear interpretation of the results.

Also read: Why Phentermine Shows Up on a Drug Test and How to Avoid It.

What Affects Detection Time?

Several factors determine how long phentermine stays in one’s system.

  • Age: Older people take a longer time to metabolize phentermine.
  • Dosage: Phentermine will remain in the system for longer than the expected time periods if more than the recommended dose is consumed.
  • Metabolism: Younger people’s metabolism will clear phentermine out of their system in three to five days, but could be longer for older people.

Getting Phentermine Out of One’s System

It is not recommended that phentermine users stop taking the medication altogether, but rather allow it to taper off. Gradually stopping will reduce the effects on the body, and after the last consumed dose phentermine should leave the body in a matter of two days.

There is no way to speed up the phentermine expulsion process that is healthy.

Because phentermine is stored in body fat, burning said fat can help speed things along a bit, but if a test for phentermine is pending, it is important to either disclose the prescription for it (in which case it will not present a problem on the test) or to stop it a week ahead of testing.

Because the prescription for phentermine is for multiple weeks, it is important to plan ahead if a test is expected.

Overdose Symptoms

Because phentermine has similar neurotransmitter impacts that amphetamines will, the prescriptions are tied in with strongest regulations and permitted for only short periods of time.

It is also not a recommended medication for those with stimulant-use disorders.

Phentermine does come with some serious side effects including restlessness, tremors, dizziness, insomnia, heart palpitations, heightened blood pressure, chest pain, as well as ankle and leg swelling.

Symptoms of phentermine overdose could include:

  • Nausea
  • Vomiting
  • Severe restlessness
  • Diarrhea
  • Seizures
  • Weakened pulse
  • Hallucinations
  • Fatigue
  • Depression
  • Stomach cramps
  • Slowed breathing
  • Irregular heartbeats
If an overdose is suspected, it is important to call poison control at 1-800-222-1222, and 911 immediately if the person has collapsed or stopped breathing.

Drug Interactions

Due to phentermine’s chemical composition, it interacts with certain other drugs and supplements. For that reason, discussing your phentermine intake with your physician is imperative ahead of getting any new medications. Especially concerning are interactions that involve:

  • Monoamine oxidase inhibitors (MAOIs) like Nardil (phenelzine) and Marplan (isocarboxazid)
  • Selective Serotonin reuptake inhibitors (SSRIs) like Prozac (fluoxetine), Paxil (paroxetine), Zoloft (sertraline), and Luvox (fluvoxamine)

Physicians should also be made aware of any pre-existing heart conditions like arteriosclerosis or elevated blood pressure. Also, it is important to make the doctor aware of hyperthyroidism.

When taking phentermine consumption of alcohol is advised against as the combination of the two intensifies phentermine’s effects.

Also read: Phentermine Drug Interactions.

Getting Help

As with most medications of this type, stopping phentermine intake can result in certain withdrawal symptoms. They tend to reach their peak within the first couple of days, diminishing slowly over the following week.

Some of the most common withdrawal symptoms include:

  • High blood pressure
  • Stomach pain
  • Headaches
  • Fatigue
  • Diarrhea
  • Menstrual irregularities
  • Irritability
  • Heart palpitation
  • Memory loss
  • Insomnia

If a high dose of phentermine is regularly ingested, and the intake suddenly stops, more severe effects are likely to follow, including:

  • Tremors
  • Seizures
  • Nerve damage
  • Strokes
  • Congestive heart failure
  • Cardiac arrest

While phentermine can help with weight loss goals when consumed with prescriptions, it is always important to recognize the potential risks involved with its consumption, including the development of a stimulant disorder and developing a phentermine dependence.

When phentermine is no longer consumed, concentration tends to degrade. Many erroneously try to remedy this by taking either more or less than the prescribed dosage. Doing so, however, is a hindrance to one’s cardiovascular health.

It is important to speak with a mental health professional if phentermine cravings are interfering with one’s daily life.

Many people suffering from substance reliance find help in speaking at group therapy sessions where they learn to understand the reason for this condition and learn coping tactics, and strategies for slowly weaning themselves off the substance.

Abstinence and harm reduction programs are also available.

If you are suffering from phentermine addiction symptoms, please seek out help. Substance Abuse and Mental Health Services Administration’s Behavioral Health can offer locations for seeking treatments.

If your doctor is against prescribing phentermine, then they likely have your best interests at heart. It is important to lose weight, of course, but overall health and well-being are always going to be their primary concern.

Rather, consider trying one of the prescription-free phentermine alternatives. There are several on the market.

These dietary supplements will not show up on a drug test in your urine, blood, and hair as they do not contain ingredients similar to amphetamine. With these alternatives, you can benefit from the appetite-suppressing effects and energy boost without the worry of failing the drug test.

Last updated: Feb 9, 2021. Bookmark the permalink.

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