About Phentermine

Obesity is a growing health concern worldwide. According to the World Health Organization (WHO), in 2022, 2.5 billion adults aged 18 years and older were overweight, including over 890 million adults who were living with obesity.

As individuals seek practical solutions for weight loss, prescription medications like Phentermine can offer a viable option. Approved by the FDA and classified as a Schedule IV controlled substance, Phentermine serves as an appetite suppressant to aid in the treatment of obesity.

What is Phentermine?

Phentermine is a prescription medication used as an appetite suppressant to help individuals lose weight. It belongs to a class of drugs known as sympathomimetic amines, which stimulate the nervous system, reducing hunger and making it easier for people to adhere to a calorie-restricted diet.

FDA Approval and Classification

The Food and Drug Administration (FDA) approved Phentermine 1959 for short-term obesity treatment.

With its classification as a Schedule IV controlled substance, Phentermine’s potential for misuse is recognized but deemed to be low. Schedule IV substances are defined as drugs with a low potential for abuse and a low risk of dependence. However, this classification also means that its prescription and distribution are strictly regulated to ensure that it is used safely and effectively.

Phentermine requires careful monitoring to ensure patient safety and prevent misuse.

How Phentermine Works

Phentermine works by releasing certain chemicals in the brain that control appetite.

Precisely, Phentermine activates adrenergic receptors and triggers the fight-or-flight response. This releases more norepinephrine while also limiting the reuptake and breakdown of dopamine. The increased dopamine and norepinephrine amplify signals to the hypothalamus that the body has sufficient energy stores and doesn’t need additional caloric intake.

Additionally, dopamine and norepinephrine regulate the mesolimbic reward pathway that controls motivation and cravings around food. By increasing these catecholamine neurotransmitters, Phentermine blocks compulsive urges to eat and overconsume calories. This physiological response allows individuals to better comply with calorie-controlled diets until the medication is no longer needed and lifestyle habits can sustain weight loss.

Who Should Consider Phentermine?

Phentermine is generally prescribed for individuals who are classified as obese, with a Body Mass Index (BMI) of 30 or higher.

In some cases, it may also be prescribed to individuals with a BMI of 27 or higher if they have weight-related medical conditions such as hypertension, diabetes, or high cholesterol.

Your health history and potential contraindications are crucial factors in determining whether Phentermine suits you.

Effectiveness of Phentermine

According to several scientific studies, patients taking Phentermine lost an average of 5% to 10% of their body weight compared to placebo groups over 12 weeks. Patients also experienced a more pronounced reduction in waist circumference and improvements in metabolic health markers compared to non-users (sources: Diabetes, Obesity and Metabolism; Yonsei Medical Journal; British Medical Journal; Pharmatherapeutica).

Dosage and Administration

Phentermine is available in various forms, including tablets and extended-release capsules.

The usual starting dose is 15 to 37.5 mg once daily, taken before breakfast or 1-2 hours after breakfast. It is essential to closely follow your healthcare provider’s instructions to achieve the best results.

Side Effects and Considerations

Like all medications, Phentermine comes with potential side effects, which can range from mild to severe.

Common side effects include:

  • Dry mouth
  • Insomnia
  • Nervousness
  • Constipation

More severe side effects can include increased heart rate, elevated blood pressure, shortness of breath, chest pain, difficulty breathing, severe headache, seizure, and signs of an allergic reaction such as rash, itching, or swelling of the face, tongue, or throat.

It is vital to consult your healthcare provider for a thorough evaluation before starting Phentermine to ensure its safety.


Phentermine is not suitable for everyone. It is contraindicated in individuals with a history of:

  • Cardiovascular disease
  • Hyperthyroidism
  • Glaucoma
  • Drug abuse

Pregnant or breastfeeding women should also avoid taking Phentermine.

Long-term Use and Dependency

Given its classification as a Schedule IV controlled substance, there is a risk of dependency with prolonged use of Phentermine. Healthcare providers generally recommend using it only temporarily to minimize this risk.

Studies suggest that Phentermine’s benefits diminish after a few weeks of continuous use, making it less effective for long-term weight management (source: International Journal of Clinical Pharmacology and Therapeutics).

Lifestyle Changes for Sustained Weight Loss

While Phentermine can significantly boost your weight loss efforts, it should be part of a comprehensive weight management plan. This plan should include:

  • A balanced, reduced-calorie diet
  • Regular physical activity
  • Behavioral therapy to address emotional eating

These lifestyle changes can help ensure sustained weight loss and improved health.


Phentermine is a well-established medication approved by the FDA for the short-term treatment of obesity. As an appetite suppressant, it can help individuals jumpstart their weight loss journey when used in conjunction with lifestyle changes. If you’re considering Phentermine, consult your healthcare provider to ensure it’s the right option.