Phentermine: Benefits, Risks And Drug Test Effects!

Phentermine: Benefits, Risks And Drug Test Effects!


Phentermine is an amphetamine-like substance that is used for suppressing appetite. Since phentermine is similar to AMP/amphetamine in many ways, you can get yourself tested for AMP before your pre-employment drug test. 

Phentermine may not show up unless it is specifically tested for, but it may show up as amphetamine in your standard 5 panel drug test.

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Phentermine was first approved by the FDA in 1959 for use in the short-term management of obesity. Phentermine helps lose weight by decreasing appetite while making you feel energetic and boosted. 

Phentermine is a Schedule IV drug and belongs to a class of drugs called sympathomimetic amines. Long-term use of sympathomimetic drugs such as phentermine has a potential for abuse. 

How Effective Is Phentermine?

Phentermine is one of the most effective medications for losing weight. According to research, people lost an average of 18 lbs. in nine weeks after taking phentermine. In addition, clinical studies reveal that phentermine can produce significant weight loss even after one year of taking the drug and, in some cases, double the weight loss experienced in a short period. 

Also, a study published by "The archives of Internal Medicine" shows that phentermine can help maintain weight loss for at least two years. Phentermine is particularly effective for people with a BMI ranging from 30 to 35. Also, some researchers suggest that phentermine effectively treats binge eating disorders. Thus, phentermine is a very effective option for people struggling with obesity.

Does Phentermine Have Any Side Effects?

Like many other prescription drugs, phentermine can have side effects and complications often associated with obesity. These include:

  • Chest Pain: Some people may experience chest pain after taking phentermine. The pain may be mild and short-lived, but it can also be severe.
  • Dry mouth: Some people experience dry mouth sensations when taking phentermine. It is one of the common side effects, although it often resolves on its own with time.
  • Headaches: Another common side effect of taking phentermine is headaches. However, they are often not severe and soon disappear once you stop the medication.
  • Palpitation: Palpitation is another side effect of phentermine. It is a sensation of a fast heartbeat and may become severe.
  • Swelling of Legs and Ankles: Some people with a pre-existing medical condition may experience swelling of their legs and ankles while taking phentermine. This side effect is normally not severe, but it can become serious.

Does Phentermine show up on a drug test?

Phentermine has a chemical structure similar to amphetamine and can show up on a drug test that screens for amphetamine. A urine drug test is the most prevalent method for screening illicit substances in workplace drug testing. A standard urinalysis typically screens for MMJ, opiates, phencyclidine (PCP), cocaine, and amphetamines.

Can Phentermine get you high?

Like many prescription medicines such as opioids, phentermine can create a high, especially taken in large doses. Snorting, smoking, and mixing with alcohol are popular ways in which phentermine is abused.

Using phentermine in ways other than prescribed by your healthcare provider can put you at high risk of addiction, tissue damage in the lungs and esophagus, and cardiovascular complications.

How long does Phentermine stay in your system?

The duration for which a drug lasts in the system depends on several factors such as heredity, the rate of metabolism, the quantity consumed, the quality of the substance, hydration, and, importantly, the frequency of drug use.

Phentermine has a half-life of about 16-31 hours. It can be detectable in the urine for 1-3 days. However, heavy and long-term use of phentermine may result in having much longer detection windows.

Moreover, phentermine is a mind-altering medication, and you may experience withdrawal symptoms when stopping it.

Phentermine Withdrawal Symptoms

If you have been consuming phentermine for a while, abruptly stopping it may cause withdrawal symptoms. The symptoms will usually begin after several hours of stopping, and the severity of these symptoms depends on the amount you have taken. Phentermine withdrawal symptoms include:

  1. Headache: Headaches are a common side-effect of taking phentermine. It may be caused by the withdrawal of the drug and not necessarily by the medication itself.
  2. Nausea: Nausea is the most common effect when stopping phentermine. It results from overuse, although withdrawal symptoms may also cause it.
  3. Lack of energy: Phentermine is linked to increased energy and alertness in the body. Consequently, stopping it abruptly may cause you to feel tired and weak due to the reduction of energy.
  4. Anxiety: Some people face anxiety symptoms during phentermine withdrawal, especially if they were already anxious before taking the drug.
  5. Diarrhea: Diarrhea is one of phentermine's most serious side effects. It occurs when your digestive system fails to absorb nutrients from food, which is also a sign of withdrawal.
  6. High Blood pressure: Increased blood pressure is usually one of the most severe withdrawal symptoms. It can cause other complications, such as a stroke.
  7. Stomach Pain: Stomach pain is one of phentermine's most common side effects. It might be mild or severe and can be caused by withdrawal symptoms or drug intake.
  8. Menstrual irregularities: Menstrual irregularities are another common phentermine withdrawal symptom. It may begin several days after stopping the medication.
  9. Insomnia: Insomnia occurs when you can't go to sleep, keep sleeping or wake up frequently during the night. It can be caused by withdrawal symptoms or the intake of phentermine. You should consult your doctor if you have any questions regarding insomnia and phentermine use.
  10. Memory loss: Memory loss is one of the least common phentermine withdrawal symptoms. It may become more severe over time as you continue using phentermine.

Does Phentermine cause a false positive drug test?

Phentermine can give a false positive in a drug test. Because of its structural characteristics that closely resemble amphetamine, most panel drug tests will detect phentermine and give a positive result.

If you know that you will be drug tested, it is essential to inform your direct supervisor, employer, or the medical review officer (MRO) prior to the testing. In such cases, a false positive will be treated as a negative.

Does Phentermine help you burn fat and lose weight?

Phentermine increases energy in the body while reducing appetite and minimizing craving for food. To get satisfactory results, combining with an exercise plan and introducing healthy diet regimes is recommended.

Do You Gain Weight After Stopping Phentermine?

Research shows that people gain weight after stopping phentermine, but not as much as before taking it. You can limit weight gain after quitting phentermine with the proper diet and exercise plan. 

  1. Some people may experience water retention after taking phentermine.
  2. Others may gain weight due to a poor diet and lack of exercise.
  3. In some cases, people can also gain weight when they stop taking their medication without proper diet and exercise.

Also, according to the American Society of Anesthesiologists, you must have a physician's written order before stopping the medication. 

How To Not Gain Weight After Stopping Phentermine?

It is vital to note that if you stop taking phentermine, it won't automatically make you gain weight. It is fairly normal for people to gain a little weight after stopping medication for obesity. 

Several factors can determine this. The most important is a healthy diet plan and exercise regimen. In addition, take your medication as prescribed by your physician to avoid severe withdrawal effects. When going off the medication, it is recommended to follow a few other tips to prevent any weight gain:

  • Maintain a healthy diet plan and stay away from temptation.
  • Continue your exercise schedule to burn more calories and maintain a healthy lifestyle.
  • Drink water and get the proper amount of rest.
  • Don't be too harsh on yourself, and don't beat yourself up if you gain some weight.

What Happens If You Stop Taking Phentermines Suddenly?

The sudden discontinuation of phentermine can cause a rebound effect in the body, causing specific withdrawal effects. While phentermine is an appetite suppressant, it also helps regulate blood pressure and heart rate. 

The correct way to discontinue the medication is to taper it off slowly. Also, to avoid feeling the rebound effect, it's recommended that phentermine should be taken in low doses. Moreover, when you go off of phentermine, you should try to get as much sleep as possible and recover from the effects. 

FDA guidelines and recommendations state that you should seek medical consultation with your physician if you have been using phentermine for an extended period or if you feel you are dependent on the drug. You might want to consult your doctor about slowly transitioning off the medication by reducing the dosage over weeks.

How to Pass a Drug Test of Phentermine?

Some individuals who have taken phentermine in the past have been terminated from employment due to a positive drug test. Fortunately, there are several ways to pass a drug test while taking phentermine. 

If you want to avoid failure of a drug test due to the use of phentermine, we recommend that you follow these simple steps:

  • Try On Your Own Before Trying A Detoxification Program
  • If you have been taking phentermine, you may be concerned that a drug test will expose the fact that you're using it. However, several home remedies may help you to pass a drug test on your own such as:

    1. Drink Water

    Drink plenty of water beforehand to dilute your urine. It will make it easier for you to pass a drug test. Wait for the final hour before taking a test, and then drink more water than you usually do.

    2. Exercise

    When you exercise, your body burns fat. Some individuals find that exercising a few hours before the test allows the fats to exit their system, leading to a diluted urine sample.

    3. Lemon Juice

    Lemon juice is another great natural way to pass a drug test using phentermine. It will help to dilute your urine sample and eliminate traces of phentermine.

  • Check Your Test
  • After deciding to try home remedies for detoxification, you must check the type of drug test you'll face, as each drug test is different. You should remember that there are blood, urine and hair drug tests. Also, some companies may use a combination of these tests or even a saliva test. You can try at-home drug testing kits to test the drug levels before facing your real test.

  • B12 Injection
  • If you have been taking phentermine, a B12 injection may help you to pass a drug test. Yet, this method is not always effective and usually takes time to work on your body. It is always recommended to try detoxification methods on your own before going to a detox center.

    Bottom Line

    Phentermine is one of the most popular weight loss medications available in the United States.  It helps suppress appetite and boost energy. This being said, it should be combined with a healthy exercise and diet regimen. Additionally, you have to be careful not to use phentermine for body toning as it is a prescription medicine for the management of obesity and carries serious side effects.

    This amphetamine-like substance can potentially cause a wide range of complications such as fatigue, dry mouth, dizziness, constipation, insomnia, tingling or prickling sensation, and increased heart rate.

    Some users may also experience withdrawal symptoms during the medication. Because of its structural characteristics that closely resemble amphetamine, most panel drug tests will detect phentermine and give a false positive result.


    Does Phentermine give you energy?

    Phentermine stimulates the secretion of noradrenaline in the brain, and noradrenaline, in turn, suppresses appetite by stimulating adrenergic receptors. It also stimulates the release of dopamine and adrenalin that increases energy and alertness in the body.

    Phentermine vs. Amphetamine - What is the Difference?

    Phentermine is related chemically to amphetamine. Both phentermine and amphetamine stimulate the central nervous system and induce the same adrenergic receptors in the brain.

    The most crucial difference between phentermine and amphetamine is in the amount of dopamine released. The release of dopamine is much higher in amphetamine in comparison to phentermine which makes it highly addictive.

    Does Phentermine cause hair loss?

    Long-term phentermine use, in some instances, may lead to hair loss. Most phentermine users may experience hair loss around three months into their treatment. Some studies point to the relationship between loss of visible hair and amphetamine.

    Not much is known about the exact cause of hair loss among phentermine users.  It is thought to be an effect of increased calorie restriction and elimination in the body. Hair loss among phentermine users may last as long as the medication is taken for treating weight loss.


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