Introduction

When it comes to prescription weight loss medications, Zepbound and Phentermine are two of the most well-known—but they couldn’t be more different.

Zepbound is a modern, hormone-based injectable approved for long-term use. Phentermine is an older, stimulant-based pill used short-term to suppress appetite.

So which one works better for weight loss—and which is right for you? This guide compares Zepbound vs Phentermine side by side, covering results, safety, cost, and who each option is best for.

Quick Overview

Feature	Zepbound	Phentermine
FDA Approved For	Chronic weight management	Short-term weight loss (12 weeks)
Active Ingredient	Tirzepatide	Phentermine (stimulant)
Method of Use	Weekly injection	Daily oral tablet
Avg. Weight Loss	15–22.5% of body weight	5–10% of body weight
Duration	Long-term	Short-term
Control Classification	Not controlled substance	Schedule IV controlled substance

How They Work

Zepbound (tirzepatide):

• Mimics GLP-1 and GIP hormones

• Slows digestion and suppresses appetite

• Improves insulin sensitivity and blood sugar control

• Supports long-term fat loss and metabolic health

Phentermine:

• Acts as a stimulant, similar to amphetamines

• Increases norepinephrine to suppress appetite

• Short-term appetite reduction without long-term metabolic benefits

Weight Loss Comparison

Medication	Typical Pounds Lost	Timeframe
Zepbound	25–60+ lbs	3–12 months+
Phentermine	10–25 lbs	1–3 months

Zepbound leads to more consistent, long-term weight loss, while phentermine may offer faster short-term drops.

Source: Zepbound SURMOUNT-1 Trial – NEJM

Side Effects

Zepbound:

• Nausea, constipation, fatigue (usually improves with time)

• Low risk of addiction

• No stimulant side effects

Phentermine:

• Increased heart rate and blood pressure

• Insomnia, jitteriness, anxiety

• Risk of dependence or abuse

• May lose effectiveness over time

Zepbound is better tolerated long term and designed for sustainable use. Phentermine is not intended for chronic use.

Insurance & Cost Comparison

Medication	Retail Price (U.S.)	With Discounts	Covered by Insurance?
Zepbound	~$1,060/month	As low as $25/month w/ savings card	Often (with PA)
Phentermine	~$20–$50/month	Generic available	Usually covered short-term

Apply here: Zepbound Savings Card

Who Is Zepbound Best For?

Adults with:

• BMI ≥30 or ≥27 with a health condition

• PCOS, insulin resistance, or prediabetes

• A history of weight regain after other programs

• Need for long-term weight control

Who Is Phentermine Best For?

Adults who:

• Need short-term weight loss for a medical procedure or jumpstart

• Do not have high blood pressure, heart disease, or anxiety

• Are under a provider’s close supervision

• Do not have a history of stimulant sensitivity or addiction

Can You Combine Them?

In some cases, yes—Zepbound + low-dose phentermine may be prescribed together short-term to:

• Break through a plateau

• Kickstart early results

• Curb cravings while titrating Zepbound

Only use this combo under medical supervision.

Final Thoughts

Zepbound is the better long-term solution, offering consistent weight loss with metabolic benefits. Phentermine may work faster in the short term, but it’s not sustainable for most people—and comes with stimulant-related side effects.

Choose Zepbound for long-term fat loss, hormonal regulation, and metabolic reset
Use Phentermine cautiously for short bursts under supervision
Talk to your provider about combining or transitioning from one to the other

Visit  Weight Loss Medication Comparison Article for detailed breakdowns.