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Semaglutide vs. Phentermine

Semaglutide vs. Phentermine
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In the realm of weight loss medications, semaglutide and phentermine stand out as two of the most sought-after options. Both have been heralded for their effectiveness, but they operate through different mechanisms and carry distinct side effects. In this article, we’ll break down the key differences between the medications to help you make an informed decision about your medical weight loss.

What Is Semaglutide and How Does it Work for Weight Loss?

Semaglutide is a weight loss medication originally developed to treat type 2 diabetes that belongs to a drug class known as GLP-1 receptor agonists. It works by mimicking the action of the incretin hormone, which is naturally produced in the body after eating. This action slows down gastric emptying, meaning it keeps food in the stomach for longer periods, thus promoting a feeling of fullness and reducing appetite.

Additionally, semaglutide acts on the brain to curb cravings. Combined, these effects contribute to weight loss by reducing caloric intake and encouraging more mindful eating habits.

Semaglutide for weight loss is primarily administered once a week through subcutaneous injection, though it’s also available in pill form.

What Is Phentermine and How Does it Work for Weight Loss?

Phentermine is a prescription medication that functions as a central nervous system stimulant, similar in nature to an amphetamine. It’s typically prescribed for short-term use to help overweight individuals who’ve failed to lose weight through diet and exercise.

Phentermine facilitates weight loss by suppressing appetite, thereby reducing food intake. It achieves this effect by releasing chemicals in the brain that control appetite, making the user feel fuller for longer and mitigating cravings. Phentermine is taken once a day as an oral tablet.

What Are the Side Effects of Semaglutide for Weight Loss?

Like any medication, semaglutide carries a range of potential side effects. These can include:

  • Nausea and vomiting
  • Diarrhea
  • Constipation
  • Abdominal pain
  • Headaches
  • Fatigue

While the majority of these side effects are manageable and subside over time, there are more rare but severe side effects associated with semaglutide, including:

  • Pancreatitis
  • Gallbladder disease
  • Kidney injury or failure
  • Severe allergic reactions
  • Low blood sugar levels (hypoglycemia)
Side Effects of Phentermine for Weight Loss

What Are the Side Effects of Phentermine for Weight Loss?

When using phentermine for weight loss, the following side effects can occur:

  • Increased heart rate
  • Dry mouth
  • Insomnia
  • Dizziness
  • Constipation or diarrhea

More rare but severe side effects include elevated blood pressure and heart palpitations.

Read More about: Semaglutide vs. Liraglutide

Is Semaglutide More Effective Than Phentermine for Weight Loss?

Recent studies suggest that semaglutide may offer more substantial and sustained weight loss than phentermine, with the added benefit of improving glycemic control in patients with type 2 diabetes. However, the choice between semaglutide and phentermine should be made based on your individual health profile and your doctor’s guidance.

Can I Take Semaglutide and Phentermine Together?

Semaglutide and phentermine can generally be used together since they don’t interact with each other. That said, their simultaneous use should be approached with caution.

Which Weight Loss Medication Should You Take?

When deciding between semaglutide and phentermine for weight loss, you should consider several factors, including your medical history, weight loss goals, and the medications’ side effects.

Semaglutide is generally used for long-term weight loss, while phentermine is designed for short-term use.

It’s important to consult a doctor to determine the most appropriate option for you.


Semaglutide and phentermine work in different ways and carry different side effects, but they can both be effective for weight loss. Ultimately, though, the decision between these medications should only be made after a discussion with your doctor and a careful consideration of your medical history, weight loss objectives, and anticipated reaction to each drug.

If you’re seeking to join a medical weight loss program, look no further than the Sanctuary Wellness Institute. Participants in our program get semaglutide injections delivered straight to their homes for self-administration and attend virtual doctor’s appointments to receive guidance and track their progress. Book an evaluation today to discover whether you’re eligible for weight loss injections.

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