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Weight Loss drugs, supplements, and products have been growing rapidly in recent years with hundreds of different options now readily available throughout the dieting industry. Most of these products are available to purchase online or in health food stores nationwide.

These products generally come with a minimal risk to your health and can have enormous health benefits for the user, and when combined with regular exercise and a healthy, well-balanced diet, it can become extremely easy to obtain and keep your ideal figure.

However, some people still struggle to reach their goals with tried and tested methods and may need to consider prescription medications, this can be for a wide range of reasons.

Phentermine is a prescription medication and this article will provide you with all of the information you need to understand what it is, what it does, the potential side effects, and if it is for you.

What Is Phentermine?

Phentermine received FDA approval as an appetite-suppressing drug in 1959 and marketed as an appetite-suppressing and fat burning agent known as ‘fen-phen’. It is chemically synthesized from phenyl-tertiary-butylamine and is pharmacology similar to amphetamine. It is also the most widely prescribed obesity medication in adults. [1]

What Does Phentermine Do?

Although the underlying chemical and biological processes are relatively unknown, Phentermine helps to suppress appetite and increase cardiovascular output in the patient. It is said to release norepinephrine, a neurotransmitter involved in stress responses (fight-or-flight reactions), and reduces hunger sensation. Phentermine stimulates the central nervous system and Increases Sympathetic Activity. [2]

How Does Phentermine Work?

Phentermine releases a chemical in the brain called ‘norepinephrine’ which reduces the levels of hunger felt by the patient. It also stimulates the central nervous system and cardiovascular system, which in turn, can increase your metabolic rate, increasing the rate at which your body can burn fat.

By reducing your sensation for hunger, this medication will suppress your appetite encouraging you to consume less calories meaning your body will turn to fat storage for energy.

What Are The Side-Effects Of Phentermine?

Here are some side effects experienced by users, however, the incident rate is not known and appears to be sporadic.

Some potential side effects of taking Phentermine are:

  • Chest pain
  • decreased ability to exercise
  • dizziness
  • fainting
  • fast, irregular, pounding, or racing heartbeat or pulse
  • headache
  • numbness or tingling in the arms or legs
  • swelling of the feet or lower legs
  • trembling or shaking of the legs, arms, hands, or feet
  • trouble breathing
  • trouble with thinking, speaking, or walking
  • Weakness
  • Decreased interest in sexual intercourse
  • difficulty having a bowel movement (stool)
  • dry mouth
  • false or unusual sense of well-being
  • hives or welts, itching, or skin rash
  • inability to have or keep an erection
  • increased in sexual ability, desire, drive, or performance
  • increased interest in sexual intercourse
  • loss in sexual ability, desire, drive, or performance
  • redness of the skin

Do Not Take Phentermine If: 

  • If you have a history of heart disease (coronary artery disease, heart rhythm problems, congestive heart failure, stroke)
  • Severe or uncontrolled high blood pressure
  • Overactive thyroid
  • History of pulmonary hypertension
  • If you are pregnant and/or breast-feeding: Not recommended for use by pregnant or lactating women.
  • If you’re a child under the age of 18: Not intended for use by persons under the age of 18.

Is Phentermine Safe?

 Phentermine has been approved by the FDA and considered a safe medication, however, it comes with a wide range of potential side effects and has been known to cause Primary Pulmonary Hypertension (PPH) – a rare, frequently fatal disease of the lungs.

Serious regurgitant cardiac valvular disease, primarily affecting the mitral, aortic and/or tricuspid valves, has been reported in otherwise healthy persons who had taken a combination of phentermine with fenfluramine or dexfenfluramine for weight loss.

It is unclear just how safe this medication is and more research would be required to give a definitive answer. [3]

Has Phentermine Caused Deaths?

There have not been any deaths linked to this medication, however, there have been other potentially fatal health issues reported in relation to respiratory and cardiovascular systems.

Does Phentermine Actually Work?

There have been many clinical trials that do show Phentermine delivers results for the purpose of weight loss. It is important to note that many of the trials also state a healthy lifestyle being a key component of sustained weight loss in conjunction with Phentermine. [4]


Phentermine is an approved FDA drug and has been prescribed to millions of people worldwide as an appetite suppressant. The medication does deliver results in terms of weight loss as it actively reduces your sensation of hunger, which in turn, will naturally result in the user consuming fewer calories. This would lead to the body turning to excess fat storage to provide fuel for the body.

Phentermine also acts as a stimulant to the body’s central nervous system which could also increase cardiovascular and metabolic rate within patients, again, causing the body to increase the amount of fat it would normally burn.

There are some well-founded health concerns and side effects that come with this medication that appears to be very random and unpredictable between individual users. Adverse side effects can result in potentially fatal cardiovascular, and respiratory issues.

There many other tried and tested methods you should attempt to adopt in order to lose weight before considering prescribed medication.

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Fact Checked

This article has been reviewed and fact-checked by a certified nutritionist, and only uses information from credible academic sources.