Phentermine Side Effects

The Common and Less Common Adverse Effects and Contraindicated of Phentermine Diet Pills

Phentermine side effects

Together with its expected action, phentermine may bring undesirable adverse effects, often an indication of severe lung and heart disorders. Here you can learn about Phentermine side effects, the contraindicated and the Phentermine overdose effects.

Phentermine is a drug with stimulatory action that is chemically related to amphetamine. It is used as an appetite suppressant, an action which is achieved via manipulation of the central nervous system. As a drug, it is only prescribed to the morbidly obese.

You are advised to seek immediate medical attention if you experience any of the following symptoms while taking phentermine:

  • Difficulty breathing
  • Passing out
  • Chest pain
  • Trouble dealing with daily activities
  • Lower leg or feet edema
  • Extreme happiness or sadness feeling

Common Adverse Effects of Phentermine

Treatment with phentermine is associated with some adverse effects that occur rather commonly, but they are usually minor and don’t need medical intervention. Despite being unpleasant, they normally subside on their own as you continue with treatment and your body gets used to the medicine. Nevertheless, if these symptoms don’t go away or increase in intensity, please make sure to inform your doctor.

Most common phentermine-related side effects:

  • Changes in libido
  • Diarrhea
  • Constipation
  • Faintness
  • Xerostomia (dry mouth)
  • Headache
  • Insomnia (trouble sleeping)
  • Mood swings
  • Nausea
  • Tachycardia (fast heartbeat)
  • Stomach cramps
  • Fatigue
  • Altered taste sensation
  • Erectile dysfunction

Less Common Adverse Effects of Phentermine

Some adverse effects of phentermine are encountered less commonly. Not all of them are of the same level of severity, however, you are advised to notify your doctor if you notice any of the following:

  • Blurry vision
  • Being clumsy
  • Disorientation
  • Melancholy
  • Sleepiness
  • Aggravation (or “phen rage”)
  • Hypertension
  • Cardiac arrhythmias or flutter
  • Annoyance
  • Tension
  • Psychosis
  • Itching or skin rash

There may be other adverse effects not mentioned here. In case you experience any other adverse effects, please speak with your doctor.

Overdose with Phentermine

Phentermine is a drug that should be taken seriously. If you forget to take a dose, it’s better to ignore it, especially if it’s close to your next one.

If you suspect that you may have overdosed on phentermine, please contact a physician right away. The following adverse effects may signify a phentermine overdose:

  • Disorientation
  • Convulsions (seizures)
  • Vertigo
  • Rapid breathing
  • High temperature
  • Hallucinations
  • Extreme aggravation and tendency to attack
  • Abnormal heart rhythm
  • Abnormal blood pressure
  • Syncope
  • Extreme mood swings
  • Shaking, tremors or trembling
  • Overactive reflexes
  • Restlessness
  • Panic
  • Severe gastrointestinal symptoms
  • Stomach ache
  • Weakness or tiredness

If the possibility of these adverse effects worries you, maybe you should think about taking a phentermine alternative. Our recommendation is to take effective weight loss dietary supplements that will put you on track towards weight loss, while being safe and side-effect-free.


Avoid phentermine if you have an allergy to the substance. It is also contraindicated to those who have been diagnosed with any of the following conditions:

  • Coronary artery disease and other heart problems
  • Hypertension or hypotension
  • Glaucoma
  • Hyperthyroidism
  • Prior addiction to drugs or alcohol
  • Diagnosed allergies with other medications, including alcohol and amphetamines or amphetamine analogues.

To be on the safe side, always inform your doctor in case you are suffering from any chronic health problem such as hypertension, diabetes, thyroid dysfunction etc., so that he or she can weigh the benefits and the risks before deciding to prescribe you with phentermine.

Phentermine should not be taken by pregnant or lactating women, as well as children and adolescents younger than 16 years old.

Important Information when Taking Phentermine

Phentermine should be accompanied by a healthy diet plan and regular workouts. It is especially recommended for those people who suffer for co-morbid conditions besides obesity, such as hypertension, high cholesterol and abnormal blood sugar levels or diabetes. Nonetheless, many doctors use this drug for unlabeled indications as well.

Avoid taking this drug if you are on a MAO inhibitor such as Marplan, Furoxone, Azilect, Nardilm, Eldepryl and Parnate currently or during the past couple of weeks. If you ignore this advice and co-administer phentermine with a MAO inhibitor, you risk a dangerous interaction which may result in serious adverse effects.

When taking phentermine, avoid ingesting any other diet medication at the same time. Some weight loss supplements may induce fatal lung issues if taken together with phentermine. So remember to never do it, unless it is your doctor’s order.

When not taking this drug as indicated, there is a chance to alter one’s perception of reality, therefore extra caution is required when driving or doing any activity that required total focus. You should absolutely avoid drinking alcohol when using this drug, as it may increase the incidence of adverse effects.

It is important to remember that phentermine is only a small part of the entire weight loss plan. As such, it works in tandem with other elements of a weight loss regimen, such as a healthy eating plan, regular physical activity and weight monitoring. By no means is phentermine poised to handle the entire weight loss burden. In order to get the best results, strict adherence to the entire program is required.

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Last updated: April 6th, 2020 by Sarah Gonzales. Bookmark the permalink.

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