If you’re sick of not seeing the results you’ve been tirelessly working toward, it can make you think, is it time to turn to weight loss medication? There’s no shame in asking your doctor about these drugs. They may be the helping hand you need if diet and exercise changes have not done the trick.
But with so many options on the market—from injections to capsules—it can feel overwhelming knowing where to start. Wegovy and phentermine are two examples of prescription weight loss drugs that can help people with obesity (a body mass index, or BMI, of 30 or greater) or people with a BMI of 27 or greater with a weight-related health issue (1).
Still, these medications aren’t the same. For instance, one helps silence incessant hunger cues while the other makes you feel full faster. But when it comes down to Wegovy vs phentermine, which one is a better fit for you?
About the Experts
Ethan Lazarus, M.D., F.A.A.F.P. is an obesity medicine physician, Obesity Medicine Association board member, and owner of Clinical Nutrition Center in Greenwood Village, Colorado.
Dan Maselli, M.D., is a board-certified internal medicine, gastroenterology, and obesity medicine physician and the associate director of research for True You Weight Loss, a weight loss center in Cary, North Carolina.
What Is Wegovy?
Wegovy is a weekly injection prescribed to people with obesity or those who are overweight (a BMI of 27 or more) who have at least one weight-related health condition, such as hypertension or type 2 diabetes (2). Wegovy is a brand name for semaglutide. It belongs to a class of medications called glucagon-like peptide-1 receptor agonists (GLP-1 RAs) (3).
How does Wegovy work for weight loss?
Semaglutide revs weight loss by mimicking GLP-1, a hormone your body makes to regulate appetite, blood sugar, and digestion. “When we eat, our small intestine produces GLP-1, which signals our brain that we’ve eaten,” says obesity medicine physician Ethan Lazarus, M.D. Essentially, the drug helps you feel full faster and for longer, which can help you eat less and drop pounds.
If you’ve struggled to lose weight despite exercising and eating healthy, Wegovy can unlock elusive weight loss. A 2024 study of more than 17,000 adults who had a BMI of more than 27 and heart disease revealed that those who took semaglutide continued to lose weight for 65 weeks. Even more impressive: They kept the weight off. After four years on the drug, participants had kept an average of 10.2 percent of their starting weight off (4).
Wegovy doesn’t just help with weight loss—it may protect against more than 200 obesity-related complications, like coronary artery disease and type 2 diabetes, says obesity medicine physician Dan Maselli, M.D. He adds that semaglutide has been shown to reduce the risk of cardiovascular and chronic kidney diseases.
In fact, the participants from the 2024 study saw a 20 percent drop in major cardiovascular events, such as heart attack and stroke (4).
Phentermine first hit the market in 1959, making it one of the first FDA-approved weight-loss drugs (5). It belongs to a class of medications called anorectics, aka appetite suppressants, and is still one of the most-prescribed drugs for weight loss today. To get the best effects, you should swallow the capsule around the same time each day.
Phentermine is ideal for people with obesity but low heart disease risk because the drug can affect your heart rate. Your doctors can assess your risk based on your medical and family history, lab results, and dietary habits (6). You can get the generic version or its brand-name equivalents, Adipex-P and Lomaira.
How does phentermine work for weight loss?
Phentermine shrinks your appetite—it’s really that simple. It’s also a mild stimulant. “People get an energy boost from it, like having a couple of cups of coffee,” Lazarus says. The drug also taps into the brain’s appetite center, helping dial down the “food noise” that can make you constantly think about eating.
Phentermine stimulates your nervous system, which may increase your heart rate and blood pressure (7). Research suggests this physiological effect can help you feel full longer and promote weight loss.
One 2010 study published in Diabetes, Obesity, and Metabolism, showed that phentermine helped 96 percent of adults with obesity lose at least 5 percent of their body weight in 12 weeks (8). Sixty-two percent of those folks lost more than 10 percent of body weight, with additional perks like lower cholesterol.
Wegovy vs Phentermine
While Wegovy and phentermine are both prescribed to treat obesity, they’re two very different drugs.
Impact
Wegovy
Phentermine
Average weight loss
15 percent of total body weight
5 percent of total body weight
Drug form and cadence
Weekly injection
Daily pill
How long you can take it
Long-term use; often used indefinitely
FDA-approved for short-term use, but long is safe
Reason it’s prescribed
Weight loss and diabetes management
Weight loss
Type of drug
GLP-1 receptor agonist
Amphetamine-like
Cost
Expensive brand-name
Low-cost generic available
Who each drug is for
Wegovy is often recommended if you have a chronic health condition like diabetes or heart disease. “For a person with diabetes, we’re going to get a big one-two punch with Wegovy because it’s highly effective for controlling diabetes and helping with weight loss,” Lazarus explains.
Similarly, Wegovy may be a good fit if you have a history of heart attack, stroke, or peripheral vascular disease (a disorder that affects the blood vessels in the legs) (9).
Phentermine is a good option if you don’t have a lot of weight to lose and prefer a pill over an injection. On average, people lose about 5 percent of their total body weight on phentermine, compared to 15 percent on Wegovy (8, 10).
Because the drug can speed up heart rate, it’s often not recommended for those with heart issues. But, the research around this is a bit mixed. For instance, one 2012 study suggests the drug barely affects heart rate. In fact, it may even help decrease blood pressure levels (11).
Phentermine is also considered a controlled substance, so if you have a history of substance abuse, you could become addicted to this drug, Lazarus says. But the risk is still low. Research has shown that people who are prescribed phentermine long-term to treat obesity don’t develop a craving for the drug (12).
Side effects
Because the two medications have different active ingredients, they come with different potential side effects. With Wegovy, you might experience bloating, nausea and vomiting, constipation or diarrhea, headache, and fatigue, Maselli says (13).
Phentermine’s side effects are similar to other stimulants: irritability, rapid heartbeat, agitation, and insomnia. “A lot of these side effects can be avoided by starting at the lowest dose, 8 milligrams, and gradually increasing it,” Lazarus says. Cutting back on caffeine when starting phentermine can reduce some of these side effects, he adds.
Cost
The price tag is another important factor in deciding which of these two medications is best for you. Unfortunately, most insurance plans (including Medicare and Medicaid) don’t cover weight loss medications (12). Without coverage, you could shell out as much as $1,300 a month for Wegovy and roughly $30 per month for phentermine, Lazarus notes.
Short-term vs long-term use
Phentermine is usually prescribed for short-term use (about 4 months), though it’s safe—and possibly more effective—to use for longer periods of time (14). Wegovy, on the other hand, is designed for long-term use. You can take this drug indefinitely to maintain your weight loss.
The Bottom Line
Wegovy and phentermine are prescription weight loss medications. Wegovy is an injectable drug that mimics a hormone called GLP-1, to help you feel full faster. Phentermine is an oral tablet that suppresses your appetite. Wegovy may be better if you have more weight to lose: People who take the drug lose an average of 15 percent of their body weight, while phentermine users lose an average of 5 percent. However, phentermine is more budget-friendly.
Lauren Bedosky is award-winning health and fitness journalist with bylines in top magazines and websites like Redbook, LIVESTRONG.com, Runner’s World, and Men’s Health.
