Saxenda vs. Phentermine

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

Key Takeaways

  • Saxenda is a daily GLP-1 injection approved for long-term weight management, while phentermine is an oral stimulant approved only for short-term use of a few weeks.

  • Saxenda carries a boxed warning for thyroid tumors and common GI side effects, while phentermine's main risks are cardiovascular stimulation and dependence as a controlled substance.

  • Phentermine costs far less per month than Saxenda, but only Saxenda has FDA backing for sustained weight loss over time.

Saxenda vs. Phentermine Drug Summary

Saxenda

Saxenda (liraglutide) is a GLP-1 receptor agonist for chronic weight management in adults with obesity, or overweight with a weight-related condition, and in adolescents 12 to 17 with obesity. It's injected once daily, starting low and increasing weekly to a 3 mg maintenance dose.

Phentermine

Phentermine is a sympathomimetic amine, chemically similar to amphetamine, that suppresses appetite and boosts energy. It's taken as a once-daily oral tablet, but is FDA-approved only for short-term use, typically just a few weeks, alongside diet and exercise changes.

Saxenda vs. Phentermine Side Effects

Saxenda

Most common
Nausea (up to 39.3%)
Diarrhea (up to 20.9%)
Constipation (up to 19.4%)
Vomiting (up to 15.7%)

Phentermine

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

Saxenda vs. Phentermine Dosage

Saxenda

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 0.6 mg once daily Week 1
Maximum dose 3 mg once daily Week 5 onward
Dose changes 4 increases Every week

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

Saxenda vs. Phentermine Indications

Saxenda

Saxenda is FDA-approved for chronic weight management, meaning it's meant for long-term use rather than a short course. It works by mimicking a gut hormone that reduces appetite and slows digestion, and it's the only weight-loss GLP-1 approved for teens 12 to 17.

  • Chronic weight management in adults with obesity

  • Adults who are overweight with a weight-related condition

  • Adolescents 12-17 with obesity

  • Not approved for diabetes control (that's Victoza)

Phentermine

Phentermine is FDA-approved only as a short-term adjunct, typically just a few weeks, for weight reduction alongside diet, exercise, and behavior changes. It's intended for patients with a BMI of 30 or higher, or 27 or higher with an additional risk factor like high blood pressure.

  • Short-term (a few weeks) adjunct for weight loss

  • BMI of 30+, or 27+ with a risk factor

  • Used with diet, exercise, behavior changes

  • Not approved for long-term use or under age 16

Saxenda vs. Phentermine Pros and Cons

Saxenda

Saxenda has a long track record as the first GLP-1 approved specifically for weight loss, with outcomes data across adults and teens. It requires a daily injection and carries a boxed warning for thyroid C-cell tumors, and gastrointestinal side effects are common during dose escalation.

Pros

  • FDA-approved for long-term chronic weight management

  • Also approved for adolescents 12 to 17 with obesity

  • GLP-1 mechanism gives more substantial average weight loss

  • Once-daily dosing schedule is predictable and steady

Cons

  • Requires a daily self-injection, unlike a pill

  • Boxed warning for thyroid C-cell tumors

  • Common GI side effects like nausea and vomiting

  • Typically costs $1,300 to $1,350 per month without insurance

Phentermine

Phentermine has decades of clinical use and works quickly to curb appetite, but the FDA only approved it for short courses of a few weeks. As a Schedule IV controlled substance with stimulant effects, it carries risks of dependence and cardiovascular side effects like increased heart rate.

Pros

  • Oral tablet or capsule, no injections needed

  • Long history of use dating back to 1959

  • Typically costs $15 to $75 per month without insurance

  • Fast-acting appetite suppression

Cons

  • Only approved for short-term use of a few weeks

  • Schedule IV controlled substance with abuse potential

  • Can raise heart rate and blood pressure

  • Not approved for patients 16 and younger

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