Semaglutide vs Phentermine
One is a weekly injection, the other a daily pill. Completely different approaches to weight loss — here's how to choose.
See Which One You Qualify ForAt a Glance
Key differences between these two treatments
Semaglutide
Advantages
- Higher average weight loss
- Once-weekly dosing
- Cardiovascular benefits
- Long-term use approved
Considerations
- •Requires injection
- •Higher monthly cost
- •GI side effects common initially
Phentermine
Advantages
- No injections — just a pill
- Most affordable option
- Fast-acting appetite suppression
- Decades of clinical use
Considerations
- •Lower average weight loss
- •Typically prescribed short-term (3-6 months)
- •May increase heart rate
Feature Comparison
A detailed look at how these medications stack up
| Feature | Semaglutide | Phentermine |
|---|---|---|
| Monthly Price | $299/mo | $199/mo |
| How It Works | GLP-1 agonist | Sympathomimetic amine |
| How You Take It | Weekly injection | Daily oral pill |
| Avg. Weight Loss | 15-20% | 5-10% |
| When Results Start | 4-8 weeks | 2-4 weeks |
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The Bottom Line
These are fundamentally different approaches. Semaglutide is the stronger option for significant, sustained weight loss — it produces 2-3x more weight loss on average and is approved for long-term use. Phentermine is a good entry point if you prefer pills over injections, need a more affordable option, or want a short-term boost to jump-start your journey. Your physician can help you decide — or even sequence them strategically.
Two Very Different Approaches
Semaglutide and Phentermine work through completely different mechanisms, and understanding this difference is key to choosing the right one.
Semaglutide mimics a natural hormone (GLP-1) that tells your brain you're full. It fundamentally changes your relationship with hunger and food cravings.
Phentermine is a stimulant-like medication that suppresses appetite through your central nervous system. It works quickly but is typically used for shorter periods.
Weight Loss: What the Numbers Say
- Semaglutide: 15-20% of body weight over 12-18 months (STEP trials)
- Phentermine: 5-10% of body weight over 3-6 months (clinical data)
For someone weighing 220 lbs, that's roughly 33-44 lbs with semaglutide vs 11-22 lbs with phentermine.
Duration of Treatment
This is a critical difference:
- Semaglutide is FDA-approved for long-term chronic weight management. Many patients stay on it for a year or more.
- Phentermine is typically prescribed for 3-6 months. It's classified as a short-term adjunct to diet and exercise.
Who Should Choose Phentermine?
Phentermine may be the better choice if you:
- Strongly prefer taking a daily pill over weekly injections
- Need the most affordable option to get started
- Want a short-term kick-start before transitioning to lifestyle changes
- Have a smaller amount of weight to lose (under 30 lbs)
- Don't have uncontrolled high blood pressure or heart conditions
Who Should Choose Semaglutide?
Semaglutide may be the better choice if you:
- Have significant weight to lose (30+ lbs)
- Want sustained, long-term weight management
- Are comfortable with weekly injections
- Have type 2 diabetes or prediabetes
- Want cardiovascular health benefits alongside weight loss
Can You Switch Between Them?
Yes. Some patients start with phentermine to build momentum, then transition to semaglutide for sustained results. Your TMates physician can design a sequence that works for your goals and timeline.
Not sure which is right for you?
Our physicians will review your health profile and recommend the best medication for your goals.
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