Home Blog

Phentermine vs Ozempic (Semaglutide) for Weight Loss

Phentermine vs Ozempic
Written by:

Wafaa Amjad Dar


Dr. Bradley Noon



Medical Disclaimer
The medications listed on this website are provided for informational purposes only. Their inclusion does not guarantee that they will be prescribed to any individual, as treatment decisions are ultimately at the discretion of healthcare providers. This list is not exhaustive, and healthcare providers may prescribe other medications, including non-stimulant options, based on the patient’s unique health circumstances and needs. Read more

Obesity or increased weight can be caused by a variety of factors, such as genetics, lifestyle choices, or underlying health conditions. However, it is a manageable condition. Adopting a holistic approach that combines a balanced and nutritious diet, lifestyle changes, and regular physical activity can play a crucial role in weight management. In some cases, weight loss medications may be needed to aid in weight management, and a variety of options are available, including phentermine and semaglutide.

Seek guidance from healthcare professionals and get a personalized plan for achieving and maintaining a healthy weight.


Ozempic’s active ingredient semaglutide belongs to the class of glucagon-like peptide 1 (GLP-1) receptor agonists. It is primarily FDA-approved [1*] to improve blood sugar levels in patients with type 2 diabetes. However, it has demonstrated effectiveness in promoting weight loss as well when used alongside diet and exercise.

Ozempic is available as an injection for under-the-skin, or subcutaneous use. The recommended dose for weight loss is 0.25 to 0.5 mg occasionally up to 1-2 mg once weekly, with a maximum dose of 2 mg per week. Remember to discuss the dosage and other instructions with your healthcare provider.

How Does Ozempic Work?

Ozempic (semaglutide) is an analogue of GLP-1, an incretin hormone. It mimics GLP 1’s action [2*] by binding to its receptors. This results in increased insulin release from the pancreas, and increased release of glucagon. This process lowers blood sugar levels, aiding patients with diabetes.

Additionally, semaglutide affects the hypothalamus, enhancing the feeling of satiety, and influences the gut to slow down gastric emptying. Both mechanisms reduce appetite and food intake, consequently contributing to weight loss.

Is Ozempic Approved for Weight Loss?

While Ozempic, a brand name for semaglutide, is not FDA-approved for weight loss, the brand name Wegovy holds specific FDA approval for this purpose. In a 68-week double-blind clinical trial [3*] exploring the effects of administering semaglutide at 2.4 mg once weekly, participants achieved an impressive weight loss of approximately 14.9%.

The broader research, based on the two-year Semaglutide Treatment Effect in People with Obesity (STEP) clinical trial program [4*] , demonstrated an even higher weight loss of 15.2% with semaglutide. Since the maximum dose for Ozempic is 2 mg, the difference between this and 2.4 mg which is the common dose used in research may or may not impact efficacy.

How to Use Ozempic

Ozempic is a subcutaneous injection which means the prescribed dosage is administered beneath the skin at parts such as the abdomen, thigh, or upper arm. The dosage may vary, and it is crucial to follow the prescribed regimen provided by a healthcare professional.

Ozempic is available as pre-filled, disposable, single-patient-use pens that deliver the prescribed dosage. Patients are instructed to use a different site of the body part every week. Injecting in different areas ensures it is absorbed consistently, preventing lumps or skin indentations that may happen when injections are given repeatedly in the same spot.

It is important to note that Ozempic should be used in conjunction with a healthy diet and regular physical activity for optimal results.


Inform your healthcare provider about your medical history to ensure the safe use of Ozempic. 

Avoid taking Ozempic if you have:

  • A history of medullary thyroid carcinoma, multiple endocrine neoplasia syndrome type 2, or diabetic retinopathy.
  • Allergies to Semaglutide. 
  • Type 1 diabetes mellitus.
  • Diabetic ketoacidosis.

Side Effects

The most common side effects of Ozempic may include:

  • Nausea
  • Diarrhea
  • Abdominal pain
  • Constipation
  • Dizziness
  • Fatigue


Phentermine, classified as a Schedule IV controlled substance, is a sympathomimetic amine that acts as an appetite suppressant. It is FDA-approved to be used for decreasing body weight with diet and exercise. It is available in brand names Adipex [5*] and Lomaira [6*] .

Phentermine can be prescribed to obese patients with a body mass index (BMI) of 30 kg/m2 or higher. It can be considered for those with a BMI of 27 kg/m2 or higher if there are additional risk factors like controlled high blood pressure, diabetes, or hyperlipidemia.

Does Phentermine Burn Fat or Just Suppress Appetite?

Phentermine functions primarily as an anorectic, or appetite suppressant [7*] . It activates the release of neurotransmitters, mainly norepinephrine, in the brain. This stimulates beta2-adrenergic receptors, which leads to reduced feelings of hunger. Although phentermine doesn’t directly burn fat, its appetite-suppressing effects can aid in weight loss by promoting a caloric deficit, especially when combined with physical activity.

How to Use Phentermine

Phentermine is available in the form of oral capsules and tablets, with a dosage of 37.5 mg. Your healthcare provider will determine the lowest effective dosage for you depending on your BMI majorly. The average adult dosage is 37.5 mg, to be taken before breakfast or 1 to 2 hours after breakfast. It is crucial to follow the prescribed instructions and consult with a healthcare professional regularly.


Similar to any other medication, there are specific conditions when taking phentermine is not recommended. It could exacerbate the condition or lead to adverse effects, just as it may interact negatively with other drugs. Some of these situations include:

  • History of drug abuse.
  • History of cardiovascular disease like coronary artery disease, stroke, arrhythmias, congestive heart failure, or uncontrolled hypertension.;
  • Hyperthyroidism.
  • Glaucoma.
  • Pregnancy (or pregnancy planning) and breastfeeding.
  • Allergy to phentermine or components.

Side Effects

Possible side effects of phentermine include: 

  • Increased heart rate
  • High blood pressure
  • Effect on alertness
  • Restlessness
  • Various heart disease
  • Dizziness
  • Insomnia
  • Diarrhea 
  • Constipation 
  • Dry mouth

Ozempic vs Phentermine

Despite Ozempic and phentermine both being used to achieve weight loss goals, they have quite a few key differences, as discussed below: 



Active Ingredients


Phentermine hydrochloride

Drug class

GLP-1 receptor agonist

Sympathomimetic amine

Mechanism of action 

It helps to regulate blood sugar levels, decreases the feeling of hunger, and slows down gastric emptying. This contributes to weight loss when combined with a healthy diet and regular exercise.

It increases norepinephrine levels, which suppresses appetite and helps in weight loss when paired with diet and exercise.

Dosage form

Subcutaneous injection

Tablets, capsules


FDA-approved: Type 2 diabetes

Off-label: Weight loss

FDA-approved: Weight loss

Which of the Two Weight Loss Drugs Is Most Effective?

When starting your weight loss journey you may ask “Which is better, phentermine or Ozempic?”. It’s important to remember that the effectiveness of weight loss medication varies, influenced by individual factors and unique dynamics from person to person.

In a meta-analysis [8*] , semaglutide demonstrated a 13.7% weight loss, while phentermine/topiramate led to 9.1% weight loss. According to another 12-week research [9*] , semaglutide led to a 5.9% weight loss, whereas phentermine resulted in a 4.9% weight loss. Nonetheless, when making a choice, there are other factors to take into consideration.

Contact our medical professionals today for a personalized weight loss program and receive a prescription online if deemed appropriate.

Can You Take Both Phentermine and Ozempic at the Same Time?

There is limited data on taking semaglutide and phentermine together for weight loss. Since they have different mechanisms to achieve weight reduction, there may be a synergistic effect if you take semaglutide with phentermine. However, you should always consult a healthcare professional to establish a weight loss regimen. If your healthcare provider deems it necessary to use a combination of weight loss medications for your weight management, they will prescribe a suitable combination. Do not combine any medications without consulting a medical provider first.

Who Shouldn’t Take Ozempic or Phentermine

Some patients should avoid Ozempic or phentermine due to potential drug interactions and pre-existing medical conditions. Some drug interactions with phentermine involve alcohol, usage after 14 days of discontinuing monoamine oxidase inhibitors, insulin, and medications for low blood sugar. It can’t be used with adrenergic neuron blocking drugs—commonly prescribed for high blood pressure, heart diseases, and migraines. 

On the other hand, Ozempic should be avoided by individuals with a medical history of MTC or MEN 2, as well as those who are allergic to the active ingredient semaglutide. Also, Ozempic shouldn’t be taken by patients who have issues with the kidneys, pancreas, or gallbladder.

It is essential to be mindful of these interactions and consult with a healthcare professional to determine a safe course of action.


As a part of weight loss management, medications specifically semaglutide and phentermine are among the common choices. The decision between the two depends on many factors best determined by a medical professional.

Weight loss is a complex journey, and having the right guidance ensures a path that aligns with overall health and well-being. Connect with MEDvidi for online medical weight loss now to access a team of highly qualified professionals dedicated to supporting your health goals.


9 sources
  1. Ozempic
    Source link
  2. The Discovery and Development of Liraglutide and Semaglutide
    Source link
  3. Once-Weekly Semaglutide in Adults with Overweight or Obesity
    Source link
  4. Two-year effects of semaglutide in adults with overweight or obesity
    Source link
  5. Adipex
    Source link
  6. Lomaira
    Source link
  7. Effects on Weight Reduction and Safety of Short-Term Phentermine Administration in Korean Obese People
    Source link
  8. Medications for obesity management: Effectiveness and value
    Source link
  9. Weight Loss Outcomes Associated With Semaglutide Treatment for Patients With Overweight or Obesity
    Source link
Show more
Written by:

Wafaa Amjad Dar


Dr. Bradley Noon



Prioritize your mental well-being

Consult a healthcare professional online and receive a treatment plan tailored to your needs.

Recommended Articles

Join our newsletter

Sign up to receive mental health news and tips delivered right in your inbox every month.


Evidence Based

This article is based on scientific evidence, written by experts and fact checked by experts.

Our team of experts strive to be objective, unbiased, honest and to present both sides of the argument.

This article contains scientific references. The numbers
in the parentheses (1, 2, 3) are clickable links to peer-reviewed scientific papers.