Wegovy vs. Phentermine

See how Wegovy and Phentermine compare on approved uses, dosing, side effects, and cost.

Key Takeaways

  • Wegovy is a weekly injection approved for long-term weight management and cardiovascular risk reduction, while phentermine is a daily pill approved only for a few weeks of use.

  • Wegovy produces greater average weight loss in clinical trials but costs significantly more and carries a boxed warning for thyroid tumors.

  • Phentermine is inexpensive and works fast but is a controlled substance meant only for short-term use, not chronic weight management.

Wegovy vs. Phentermine Drug Summary

Wegovy

Wegovy (semaglutide) is a GLP-1 receptor agonist injected once a week under the skin. It's FDA-approved for chronic weight management in adults and adolescents 12 and older with obesity or overweight plus a weight-related condition, and to lower cardiovascular risk in adults with heart disease and excess weight. Treatment starts at a low dose and increases gradually over about four months.

Phentermine

Phentermine is an oral sympathomimetic approved in 1959 for short-term weight loss, typically prescribed for just a few weeks alongside diet and exercise. It works like a mild amphetamine, suppressing appetite by stimulating the central nervous system. Unlike Wegovy, it isn't intended for long-term or chronic weight management.

Wegovy vs. Phentermine Side Effects

Wegovy

Most common
Nausea (up to 44%)
Diarrhea (up to 30%)
Vomiting (up to 24%)
Constipation (up to 24%)

Phentermine

Most common
Insomnia (reported)
Dry mouth (reported)
Palpitation (reported)
Tachycardia (reported)

Wegovy vs. Phentermine Dosage

Wegovy

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 0.25 mg once weekly Weeks 1-4
Maximum dose 2.4 mg once weekly Week 17 onward
Dose changes 4 increases Every 4 weeks

Phentermine

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 37.5 mg once daily At the start
Maximum dose 15 mg once daily If needed
Dose changes 1 increase As tolerated

Wegovy vs. Phentermine Indications

Wegovy

Wegovy is approved for chronic weight management in adults and adolescents 12 and older who have obesity, or overweight with at least one weight-related condition, when combined with diet and exercise. It's also approved to lower the risk of major cardiovascular events like heart attack, stroke, or cardiovascular death in adults with established heart disease and obesity or overweight. This dual approval sets it apart from most other weight-loss medications.

  • Adults with obesity (BMI ≥30)

  • Adolescents 12+ and adults with overweight plus a weight-related condition

  • Adults with heart disease and excess weight, to reduce cardiovascular risk

  • Used long-term alongside diet and exercise

Phentermine

Phentermine is approved as a short-term adjunct for weight reduction in adults with obesity, or with a BMI of 27 or higher plus a weight-related risk factor. It's meant to be used for only a few weeks alongside exercise, behavioral changes, and calorie restriction. It is not approved for long-term or chronic weight management, and not for use in patients 16 and younger.

  • Adults with obesity (BMI ≥30)

  • Adults with BMI ≥27 plus a weight-related risk factor

  • Short-term use only, typically a few weeks

  • Used alongside diet, exercise, and behavior changes

Wegovy vs. Phentermine Pros and Cons

Wegovy

Wegovy has strong clinical trial data showing substantial weight loss and is the only weight-loss drug with FDA approval to reduce cardiovascular events. It requires a weekly injection and carries a boxed warning for thyroid C-cell tumors seen in animal studies. List price runs well above older weight-loss medications, and insurance coverage varies widely.

Pros

  • FDA-approved for long-term chronic weight management, not just short-term use

  • Only anti-obesity drug shown to reduce cardiovascular events in trials

  • Substantial average weight loss in clinical trials

  • Once-weekly dosing simplifies routine

Cons

  • Roughly $1,300 to $1,350 per month without insurance, before savings programs

  • Requires a subcutaneous injection rather than a pill

  • Boxed warning for thyroid C-cell tumors in animal studies

  • Common GI side effects like nausea and vomiting during dose increases

Phentermine

Phentermine has decades of real-world use and a low cost, making it accessible for short-term appetite suppression. As a Schedule IV controlled substance related to amphetamines, it carries risks of dependence, elevated heart rate, and increased blood pressure. It's approved only for a few weeks of use, not for the ongoing management most patients with obesity need.

Pros

  • Roughly $15 to $75 per month, far cheaper than many prescription options

  • Oral tablet, no injections needed

  • Long track record of use since 1959

  • Works quickly to reduce appetite

Cons

  • Approved only for short-term use (a few weeks), not chronic treatment

  • Controlled substance with risk of abuse and dependence

  • Can raise heart rate and blood pressure

  • No evidence of cardiovascular risk reduction

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