Wegovy vs. phentermine: which is better for weight loss?

With the recent rise in popularity of semaglutide medications, you’re likely familiar with Wegovy. But what about other weight loss drugs, such as phentermine? 

Phentermine (vs. Wegovy) is an oral treatment for obesity that is approved by the US Food and Drug Administration (FDA) for short-term use. Here, we explore the similarities and differences between Wegovy vs. phentermine, including uses, side effects, prices, and more. 

Here’s a quick look at how Wegovy and phentermine stack up at-a-glance. 

Wegovy (semaglutide) is a brand-name prescription medication available as a weekly subcutaneous (under-the-skin) injection or a daily oral tablet. 

The Wegovy pill is FDA-approved in combination with diet and exercise for:

• Weight loss and chronic weight management in adults with obesity or with overweight and at least one weight-related medical condition, such as type 2 diabetes, high blood pressure, or high cholesterol

• Reducing the risk of major cardiovascular problems (such as heart attack and stroke) in adults with heart disease and obesity or overweight

The Wegovy injection is FDA-approved for:

• Weight loss and chronic weight management (in combination with diet and exercise) in adults and children 12 years and older with obesity and in adults with overweight and at least one weight-related medical condition, such as type 2 diabetes, high blood pressure, or high cholesterol

• Reducing the risk of major cardiovascular problems (such as heart attack and stroke) in adults with heart disease and obesity or overweight, in combination with diet and exercise

• Treatment of noncirrhotic metabolic dysfunction-associated steatohepatitis (MASH, also known as fatty liver disease) in adults with moderate to advanced liver scarring 

Wegovy contains the same active ingredient as Ozempic: semaglutide. It belongs to a class of drugs known as glucagon-like peptide-1 (GLP-1) receptor agonists. 

Wegovy works by mimicking the effects of the naturally occurring GLP-1 hormone, which: 

• Increases insulin production, which lowers blood sugar levels

• Slows the movement of food through the gastrointestinal tract, prolonging the feeling of fullness and reducing hunger and food cravings

• Sends signals to the brain letting it know you’re full, which can further control hunger and, in turn, the amount of calories you eat 

See if you qualify

Phentermine is the active ingredient in brand-name drugs, including Adipex-P and Lomaira. It’s also available as a generic medication. 

Phentermine is an oral medication that is FDA-approved as a short-term treatment (generally 12 weeks or less) for weight loss in:

• Adults and children ages 16 and older with obesity, defined as a body mass index (BMI) of 30 kg/m2 or greater

• Adults with overweight and a BMI of 27 kg/m2 or greater with at least one weight-related health condition, such as type 2 diabetes, high blood pressure, or high cholesterol

Phentermine is part of a class of drugs called sympathomimetic anorectics. It works by suppressing appetite, which may lead people to consume fewer calories and lose weight. More specifically, phentermine has been shown to stimulate the sympathetic  nervous system (what is behind your “fight or flight” response). 

As a result, it increases levels of certain neurotransmitters, such as epinephrine and norepinephrine (aka noradrenaline), in the brain. This could also lead to increased energy and physical activity — two effects that may result in more calories being burned throughout the day and, in turn, weight loss. 

The Federal Drug Enforcement Administration (DEA) classifies phentermine as a Schedule IV controlled substance, meaning it has potential for abuse and dependency. Some healthcare providers may prescribe phentermine for longer than 12 weeks, but this is an off-label use.

How to take Wegovy 

Wegovy is available as both a weekly injection and a daily pill. 

The Wegovy injection comes in single-dose, prefilled prescription pens that are injected subcutaneously (under the skin) of the thigh, abdomen, or back of the upper arm. Wegovy is injected once a week, at any time of day, with or without food. It’s recommended to rotate through the injection sites each week. 

The Wegovy pill is an oral tablet that is taken daily in the morning on an empty stomach, at least 30 minutes before eating, drinking, or taking other medications. It should be swallowed whole with up to four ounces of water.

How to take phentermine 

Phentermine is available as an oral tablet or capsule. How you take it depends on the dosage:

• Phentermine 15 mg, 30 mg, or 37.5 mg capsules and tablets should be taken once daily, either before breakfast or 1–2 hours after breakfast.

• Phentermine 8 mg tablets should be taken three times daily, 30 minutes before meals.

Wegovy dosages 

The Wegovy injection comes in five dosage strengths: 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, and 2.4 mg. Providers typically prescribe the lowest starting dose of 0.25 mg and gradually increase every four weeks until you reach a maintenance dose of 1.7 mg or 2.4 mg. 

This gradual dosage increase (called “titration”) helps keep side effects manageable as your body adjusts to the medication. The Wegovy pill is also titrated for the same reasons. 

The Wegovy pill comes in four dosage strengths: 1.5 mg, 4 mg, 9 mg, and 25 mg. Providers typically prescribe the lowest starting dose of 1.5 mg and gradually increase it every 30 days until you reach a maintenance dose of 25 mg. 

Phentermine dosages

Phentermine tablets and capsules come in doses of 8 mg, 15 mg, 30 mg, and 37.5 mg. The tablet is scored so it can be divided for a lower dosage if needed.

The typical dosage of phentermine (15 mg, 30 mg, or 37.5 mg) is one capsule or tablet once daily, either before breakfast or 1–2 hours after breakfast. 

The typical dosage of Lomaira (8 mg of phentermine) is ½–1 tablet taken three times per day, 30 minutes before meals.

Your healthcare provider may adjust your phentermine dosage depending on how well you tolerate the medication.

Because they don’t work the same way, Wegovy and phentermine typically have different potential side effects, though some do overlap.  

Wegovy side effects

Wegovy slows digestion, which is why the most common side effects tend to be gastrointestinal. 

In some cases, Wegovy can cause serious side effects, such as gallstones, increased heart rate, and other effects. 

You shouldn’t take Wegovy if you:

• Have a personal or family history of thyroid cancer, including medullary thyroid carcinoma (MTC)

• Have a personal or family history of Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)

• Are planning on becoming pregnant, pregnant, or breastfeeding

• Are allergic to any of the ingredients in Wegovy

Its main drug interactions include medications for managing diabetes, such as insulin and oral medications, as the combination could lead to hypoglycemia (low blood sugar).

Phentermine side effects 

As a stimulant, the most common side effects of phentermine tend to affect your nervous system, such as a rapid heartbeat or difficulty sleeping. The drug also causes gastrointestinal side effects like nausea or constipation.

It may not be safe to take phentermine if you have other health conditions or are pregnant or breastfeeding. In addition to possible drug interactions, there are precautions around phentermine if you have the following:

• Heart conditions, including high blood pressure and arteriosclerosis

• Diabetes

• Glaucoma

• Uncontrolled hyperthyroidism (overactive thyroid) 

• History of drug abuse

The cost of any prescription drug — whether phentermine vs. Wegovy — depends on factors such as health insurance, savings offers, and location. That said, there’s a large discrepancy between the cost of the two weight loss medications. 

Wegovy cost

The list price of Wegovy is $1,349.02 per month for a month’s supply of the pen or the pill. But how much you may pay for Wegovy depends on several factors, such as health insurance (if any), preferred pharmacy, and location. (FYI, all pricing for prescription medications is affected by these factors.) 

If you have an insurance plan with coverage for Wegovy, you may be able to get Wegovy for as little as $25 per month with the manufacturer savings offer. 

If you don’t have insurance or prefer to pay cash, you can get Wegovy for $149–$349 on Ro, depending on the dose and form. 

• Wegovy pill: $149–$299 per month

• Wegovy pen: $199 per month

Navigating insurance coverage can be challenging, but Ro (if you’re a Ro Body member) can help. When you get Wegovy through Ro, for example, you also receive access to an insurance concierge who will navigate coverage on your behalf. That means communicating directly with your plan and handling all the necessary paperwork.

Another way to ease your burden? Ro’s GLP-1 Insurance Coverage Tracker, a free, online tool that can help you find out if your insurance covers treatment with GLP-1 medications. 

Phentermine cost 

The average out-of-pocket cost of a month’s supply of generic phentermine (37.5 mg) tends to be around $10-$24, according to SingleCare. Keep in mind, though, that those prices can vary depending on your location and pharmacy. Plus, brand-name Adipex-P or Lomaira tends to cost more. 

Just as with Wegovy, there are ways to help you avoid breaking the bank with phentermine. Manufacturers of brand-name phentermine products may offer coupons or savings programs. For example, KVK Tech, the maker of Lomaira, offers a low-cost program that caps patients’ costs at no more than $0.50 per pill.

You can also take advantage of savings cards and coupons offered through free, online services, such as SingleCare and GoodRx. Both of these can also be helpful whether you’re prescribed Wegovy vs. phentermine (or any other drug, for that matter). 

While results vary by person, Wegovy tends to be better for weight loss than phentermine. Here’s what the research shows when it comes to the effectiveness of Wegovy vs. phentermine.

Wegovy: The effectiveness of Wegovy can vary depending on the dose and form. 

• In clinical trials of the Wegovy injection, people taking 2.4 mg weekly (the highest injectable dose) lost up to 15% of their body weight in 68 weeks. 

• In clinical trials of the Wegovy pill, people taking 25 mg daily (the highest oral dose)lost nearly 14% of their body weight in 64 weeks.

Phentermine: Most research on phentermine is limited to 12 weeks, as the drug is recommended for short-term use.

• In clinical trials of phentermine, over two-thirds of people taking phentermine lost at least 5% of their body weight in 12 weeks. 

• By comparison, separate studies show that people taking Wegovy lose an average of 6% of their body weight in that same time frame.

When deciding between the two drugs, you and your healthcare provider likely will also weigh additional factors, such as tolerance for side effects, cost, or contraindications. 

See if you qualify

Wegovy and phentermine can both be effective medications for weight loss. One or the other could be a good fit for you based on your insurance coverage, weight loss goals, and personal medical situation and preferences.

• Phentermine is only approved for short-term use (up to 12 weeks) while Wegovy is approved for longer-term weight management.

• Wegovy comes in both oral and injectable formulations that are taken daily or weekly, respectively; phentermine is only available as an oral pill.

• Wegovy is generally considered to be more effective for weight loss, with people losing up to 14%--15% of their body weight in a little over a year.

• Both Wegovy and phentermine can cause side effects. Gastrointestinal ones tend to be more common with Wegovy, while phentermine can cause cardiovascular and nervous system effects.

• Without insurance, phentermine tends to be significantly more affordable than Wegovy. This is largely because phentermine is available as a generic, while Wegovy only comes as a brand-name drug.