Phentermine vs. Belviq

Trying to overcome obesity, people frequently stick to a healthy diet and constant exercises, as well as take other weight loss measures but sometimes they bring no effect.

You will ask why, but the reason is extremely simple and obvious: cases of severe obesity cannot be treated with physical workouts and diets only; they require more professional help, like pharmaceutical aid. However, another current issue appears at this point: how to select the right weight loss medication.

Phentermine and Belviq are the most discussed drugs at the market of weight loss help. Both medications produce a similar effect, but it is achieved by different active ingredients and various means.


  • promotes release of hypothalamic neurotransmitters, in particular serotonin, dopamine & norepinephrine;
  • high levels of neurotransmitters tend to blunt appetite and suppress a feeling of hunger.


  • activates 5-HT2C receptors in anorexigenic neurons in the hypothalamus;
  • causes a decrease in food intake and promotes rapid saturation due to the ability to release alpha-melanocortin stimulating hormone.

Both medications have a drastic impact on the body, thus, cannot be bought without a prescription. Besides, these drugs belong to a group of potent weight loss medications recommended for patients with severe obesity and related health conditions, such as heart problems, high blood pressure, high cholesterol, diabetes and others.

Having diverse active components, Phentermine and Belviq have different precautions, contraindications, side effects and other peculiarities.

Differences between Phentermine and Belviq

Although Phentermine and Belviq have the same indications for use, herewith these drugs have a number of differences; some of them are as follows:

Age restrictions

Dosing regimen

Anorexigenic drug Phentermine is approved for use in obese adolescents aged 16 years and older, Belviq can only be used by adults older than 18.

Both drugs are manufactured in oral solid-dosage forms with different dosage strengths and are available as immediate-release and extended-release capsules and tablets.

  • Phentermine dosing regimen is selected individually, taking into account the patient’s tolerability and his clinical response to the treatment.
  • The dosage regimen of Belviq in adults and elderly patients is the same.

Belviq logo


  • One immediate-release pill per day, in the morning before meal or within 2 hours after it;
  • Half a tablet of Phentermine 37.5mg twice a day: 18.75mg in the morning and 18.75mg early afternoon;
  • One Phentermine 8 mg tablet three times a day.

Dosing regimen

  • One Belviq 10 mg immediate-release tablet twice daily (in the morning and in the afternoon), regardless of food;
  • One Belviq 20 mg extended-release tablet once a day, regardless of food.

The recommended duration of a treatment course for Phentermine pills is no more than 12 weeks. The duration of Belviq application can make up to 24 months.