Wegovy vs Phentermine: A Comparison

Wegovy versus phentermine

With new drugs such as Wegovy being made available to the US market, the choice of weight loss medications is becoming more extensive.

As part of our series on popular weight loss drugs, we will compare the latest medication, Wegovy, with the most widely prescribed drug, phentermine, so that you can decide if one of these anti-obesity medications might assist you with losing weight.

What Is Wegovy?

Only approved by the FDA in 2021, Wegovy is the latest weight loss drug launched to support chronic weight management.

Unlike many oral weight-loss drugs, Wegovy is injected once a week using a pre-filled injector pen. The pen contains semaglutide, a drug that mimics a hormone called glucagon-like peptide-1 (GLP-1). Semaglutide, sold as well under the brand name Ozempic, reduces the appetite, making it easier to lose weight. (1)

Across several clinical trials, Wegovy led to statistically significant weight loss. Non-diabetic participants who took part in a 68-week trial showed an average weight loss of 17-18%. This weight loss was sustained throughout the trial without weight regains occurring.

In a study of patients with type 2 diabetes, individuals who received Wegovy lost around 6.2% of their baseline body weight. (2) (1)

Unlike many other weight loss medications, Wegovy can be taken long-term, which may lead to more successful weight loss outcomes. Wegovy has also been prescribed as a successful treatment strategy for weight regain occurring after bariatric surgery. (3)

What Is Phentermine?

Phentermine was first approved by the FDA in 1959 for treating obesity. Available as capsules or tablets, this weight loss medication contains phentermine hydrochloride, a stimulant with similarities to amphetamine. Phentermine rouses the central nervous system and causes the release of neurotransmitters, including epinephrine.

This aids weight loss as the heart rate increases, energy levels are boosted, and the appetite is reduced. Phentermine will work best if taken alongside a low-calorie diet. (4)

As phentermine is an older drug, it has been studied in many clinical trials. Of participants taking the maximum dose of phentermine (37.5mg daily) for 3 months, around 50% can expect to lose at least 10% of their baseline body weight.


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This average weight loss is considered clinically significant and beneficial to overall health.

Wegovy vs. Phentermine: A Side-by-Side Comparison

Wegovy and phentermine have both been proven to aid weight loss, but the two drugs work in different ways to achieve this. In the following table, we will compare Wegovy vs. phentermine to make it easier to understand the differences and similarities between the two.

Can You Take Wegovy and Phentermine Together?

Wegovy and Phentermine Together

You must not take Wegovy and phentermine together. The FDA recommends that only one weight loss product be taken at one time, including prescription drugs, over-the-counter preparations, and herbal remedies. (1)

Phentermine or Wegovy – Which One Is Better for Me?

If you are weighing up the pros and cons of Wegovy vs. phentermine, it is encouraging that both anti-obesity drugs have led to significant weight loss in clinical trials.

With an average weight loss of 17-18% for non-diabetic patients, Wegovy is an excellent choice for chronic weight management. The slow escalation schedule may help some people to avoid Wegovy’s digestive side effects.

However, this injectable has also been linked to thyroid tumors and is contraindicated in people with certain medical conditions. Wegovy is also a very expensive drug, especially if taken long-term.

As an older drug, phentermine has a long history of supporting weight loss and reducing the body mass index of obese and overweight people.

A generic pill is available, so it is an affordable option. Phentermine is available in a range of doses, and can therefore be titrated to avoid or minimize side effects. As an older drug that is commonly prescribed, some people may feel more comfortable trying phentermine as a first-line treatment for obesity.


Get your FREE Phentermine Guide!

Learn more about popular brands, dosage, side effects, results, and weight loss alternatives.

It is important that you discuss pharmaceutical weight loss options with your doctor prior to treatment to ensure you take the right drug for your individual circumstances.


1. FDA.gov (Wegovy Approval).
2. NovoNordisk.com (Wegovy Trials).
3. Gazda CL et al. Pharmacotherapies for Post-Bariatric Weight Regain: Real World Comparative Outcomes. Obesity. 2021; 29 (5): 829-836.
4. FDA.gov (Phentermine Label).
5. Phentermine.com (Phentermine). 
6. RxList.com (Wegovy).
7. Phentermine.com (Phentermine Dosage).
8. NovoMedlink.com (Wegovy Dosage).
9. Phentermine.com (Side Effects).
10. Phentermine.com (Phentermine Warnings).
11. Wegovy.com (Wegovy Use).
12. Novocare.com (Wegovy Cost Navigator).
13. BlinkHealth.com (Buy Generic Phentermine).
14. PushHealth.com (Buy Wegovy).
15. Drugs.com (Generic Wegovy).