Wegovy vs. phentermine: Differences, similarities & side effects

In this article:

• Wegovy vs. phentermine: Key differences
• Wegovy vs. phentermine: Conditions treated
• Wegovy vs. phentermine for weight loss: Which is better?
• Can you take Wegovy and phentermine together?
• Wegovy vs. phentermine: Insurance coverage and cost comparison
• Wegovy vs. phentermine side effects
• Wegovy and phentermine drug interactions
• Wegovy and phentermine drug warnings

In this article

• Wegovy vs. phentermine: Key differences
• Wegovy vs. phentermine: Conditions treated
• Wegovy vs. phentermine for weight loss: Which is better?
• Can you take Wegovy and phentermine together?
• Wegovy vs. phentermine: Insurance coverage and cost comparison
• Wegovy vs. phentermine side effects
• Wegovy and phentermine drug interactions
• Wegovy and phentermine drug warnings

When it comes to weight management, various prescription medications are available. Wegovy and phentermine are potential options for those looking to achieve and maintain an appropriate weight. Both medications may be considered for individuals with obesity or who are overweight with at least one weight-related condition, such as high blood pressure, high cholesterol, or Type 2 diabetes.

Despite their similar uses, Wegovy and phentermine are quite different. For example, Wegovy is a brand-name drug approved in 2021, while phentermine is a generic drug approved in 1959. These weight-loss drugs also differ in their active ingredients, dosages, potential side effects, and costs. Deciding between the two will depend on individual health profiles, weight loss goals, and the guidance of healthcare providers.

Read on to learn more about the similarities and differences between Wegovy and phentermine. 

Wegovy vs. phentermine: Key differences

The main difference between Wegovy and phentermine is in their active ingredients. Wegovy contains semaglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, which mimics a hormone responsible for regulating appetite and stimulating insulin release. It can make you feel fuller sooner and longer after eating, which can help reduce overall calorie intake.

On the other hand, phentermine belongs to a different class of medications known as sympathomimetic amines. It works by triggering the release of certain neurotransmitters in the brain that can decrease appetite. Phentermine works similarly to amphetamine, providing a stimulant effect that can lead to reduced hunger.

Dosing and dosage forms

Wegovy is available in an injectable form and is typically prescribed as a once-weekly injection. The dosage may vary as the treatment progresses, often starting at a low dose to adjust for tolerability.

Phentermine comes in several forms, including tablets and capsules, known under brand names such as Adipex-P and Lomaira. It also comes as a combination medication called Qsymia, which contains topiramate to aid weight loss. Phentermine is generally taken once daily.

Wegovy vs. phentermine: Comparing key differences
	Wegovy	Phentermine
Drug class	GLP-1 receptor agonist	Anorectic Sympathomimetic Stimulant
Brand/generic status	Brand only	Brand and generic available
What is the generic or brand name?	Semaglutide (generic)	Adipex-P, Lomaira, and others
What form(s) does the drug come in?	Subcutaneous injection	Oral tablet Oral capsule Extended-release capsule Orally disintegrating tablet
What is the standard dosage?	0.25 mg injected under the skin once weekly for 4 weeks. Then, the dosage is gradually increased to 1.7 or 2.4 mg once weekly	15 to 37.5 mg by mouth every morning before breakfast
How long is the typical treatment?	Long-term	Short-term use, up to 12 weeks at a time
Who typically uses the medication?	Adults and children ages 12 years and older	Adults and children ages 17 years and older

Wegovy vs. phentermine: Conditions treated

Wegovy is approved by the FDA for chronic weight management in adults and children ages 12 and older with obesity. It can also be used in adults who are overweight with at least one weight-related health condition.

In contrast, phentermine is approved to manage weight in adults and children ages 17 and older with obesity or who are overweight with weight-related conditions. Unlike Wegovy, phentermine is only approved for short-term use, up to 12 weeks at a time. 

Wegovy and phentermine should only be used with an appropriate diet and exercise plan and with guidance from a healthcare provider. 

In addition to weight loss, Wegovy has also been approved to reduce the risk of heart-related events in individuals with cardiovascular disease, also known as heart disease. Specifically, it may help reduce the risk of heart attacks, strokes, and other heart disease-related events in people who are overweight or have obesity with heart disease.

Wegovy vs. phentermine: Comparing conditions treated
Condition	Wegovy	Phentermine
Weight management for patients with a body mass index (BMI) of 30 kg/m2 or greater	Yes	Yes
Weight management for patients with a BMI of 27 kg/m2 or greater with at least one weight-related health condition	Yes	Yes
Reduce the risk of heart attacks, strokes, and heart disease-related death in people who are overweight or obese and have heart disease	Yes	No
Type 2 diabetes	Off-label	No

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

Wegovy and phentermine have been shown to be effective prescription medications for weight loss. The most appropriate option will depend on an individual’s response to the medication, potential side effects, costs, and weight loss goals.

In one meta-analysis, Wegovy was found to be more effective for weight loss than phentermine-topiramate. Over one year, people who took Wegovy experienced an average weight loss of around 14% versus 5% on phentermine-topiramate. Both medications also improved key health markers such as blood glucose and blood pressure. However, the long-term effects and safety of these drugs are still unclear.

One review found that Wegovy can lead to significant loss of body weight, similar to gastric bypass surgery. In contrast, older drugs like phentermine typically result in more modest weight loss and more side effects. However, the high cost and limited availability of newer drugs like Wegovy can create challenges.

Both Wegovy and phentermine are proven medications, but their effectiveness can vary from person to person. Always consult a healthcare professional before considering a weight-loss medication.

Can you take Wegovy and phentermine together?

Taking Wegovy and phentermine together is possible because they work differently to help with weight loss. However, the safety of using them at the same time isn’t well-studied, so there’s uncertainty about the risks and potential side effects.

More research is needed to understand the safety and effectiveness of taking these medications together. Always consult with a healthcare provider before making any changes to your medication regimen.

Wegovy vs. phentermine: Insurance coverage and cost comparison

Insurance plans do not always cover weight-loss medications. Therefore, coverage for Wegovy and phentermine will vary depending on the specific plan and individual circumstances. Medicare Part D plans don’t typically cover weight-loss drugs. 

Due to its relatively recent approval and higher cost, coverage may not be widespread for Wegovy. As a brand-name medication, Wegovy is generally more expensive than generic alternatives like phentermine. 

Without insurance, patients can often save on their prescription medications by using discounts or coupons through programs like SingleCare. You can visit the coupon pages for Wegovy and phentermine to explore potential savings.

RELATED: Can you really get Wegovy for $25 a month?

Wegovy vs. phentermine: Comparing insurance & cost
	Wegovy	Phentermine
Typically covered by insurance?	No	No
Typically covered by Medicare Part D?	No	No
Quantity	4 prefilled injection pens	30, 37.5 mg tablets
SingleCare cost	$1,195	$8

Wegovy vs. phentermine side effects

The most common side effects of Wegovy are gastrointestinal ones, including nausea, vomiting, indigestion, and stomach pain. Wegovy may also cause headaches, dizziness, diarrhea, and constipation. 

RELATED: Does Wegovy make you tired?

Because phentermine stimulates the central nervous system, its side effects include trouble sleeping (insomnia), high blood pressure, and heart palpitations. In addition, phentermine may cause headaches, dry mouth, nausea, vomiting, dizziness, diarrhea, and constipation, among other side effects. 

Both medications can potentially have more serious side effects. For example, Wegovy carries a warning about the risk of thyroid tumors, inflammation of the pancreas (pancreatitis), and gallbladder problems. Phentermine may cause heart problems and high blood pressure in the lungs. 

Wegovy vs. phentermine: Comparing side effects
	Wegovy	Phentermine
Side effect	Applicable?	Applicable?
Nausea	Yes	Yes
Vomiting	Yes	Yes
Dry mouth	No	Yes
Tremor	No	Yes
Indigestion	Yes	No
Stomach pain	Yes	No
Insomnia	No	Yes
High blood pressure	No	Yes
Palpitations	No	Yes
Headache	Yes	Yes
Diarrhea	Yes	Yes
Dizziness	Yes	Yes
Constipation	Yes	Yes

Frequency is not based on data from a head-to-head trial. This may not be a complete list of adverse effects that can occur. Please refer to your healthcare provider to learn more.

Source: DailyMed (Wegovy), DailyMed (phentermine)

Wegovy and phentermine drug interactions

Wegovy may interact with diabetes medications, including insulin. Since Wegovy can lower blood sugar levels, there’s an increased risk of low blood sugar (hypoglycemia) when taken with insulin or other drugs that also decrease blood sugar. As a result, healthcare providers often need to adjust the dosage of diabetes medications to ensure blood sugar levels remain stable and safe. People who take phentermine and experience progress with weight loss may also need adjustments in the dosages of insulin or other diabetic medications to prevent low blood sugar.

Phentermine may interact with monoamine oxidase inhibitors (MAOIs). Taking phentermine with an MAOI or within 14 days of stopping one may lead to a dangerous spike in blood pressure. It could potentially also cause serotonin syndrome, a serious condition resulting from high serotonin levels.

Phentermine can also interact with serotonergic drugs or antidepressants, such as selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and tricyclic antidepressants (TCAs). When taken with these medications, the risk of serotonin syndrome may be increased. In addition, phentermine can decrease the effectiveness of blood pressure medications since it can cause high blood pressure. 

Tell your healthcare provider about all medications you take, including prescription drugs, over-the-counter medicines, and herbal supplements, before taking Wegovy or phentermine. 

Wegovy vs. phentermine: Comparing drug interactions
Drug	Drug class	Wegovy	Phentermine
Humalog (insulin lispro) Novolog (insulin aspart) Lantus (insulin glargine) Levemir (insulin detemir)	Insulin	Yes	Yes
Glucotrol (glipizide) Amaryl (glimepiride)	Sulfonylureas	Yes	Yes
Januvia (sitagliptin) Tradjenta (linagliptin) Onglyza (saxagliptin)	DPP-4 inhibitors	Yes	Yes
Prandin (repaglinide) Starlix (nateglinide)	Glinides	Yes	Yes
Nardil (phenelzine) Parnate (tranylcypromine) Marplan (isocarboxazid)	MAOIs	No	Yes
Prozac (fluoxetine) Zoloft (sertraline) Paxil (paroxetine) Lexapro (escitalopram)	SSRIs	No	Yes
Cymbalta (duloxetine) Effexor (venlafaxine) Pristiq (desvenlafaxine)	SNRIs	No	Yes
Elavil (amitriptyline) Tofranil (imipramine) Pamelor (nortriptyline)	TCAs	No	Yes
Zestril (lisinopril) Norvasc (amlodipine) Lopressor (metoprolol) Cozaar (losartan)	Antihypertensives	No	Yes

This is not a complete list of drug interactions. Please consult your healthcare provider before taking these medications.

Wegovy and phentermine drug warnings

Phentermine is a Schedule IV controlled substance that carries a risk of misuse and dependence. It may need to be discontinued if tolerance develops, as increasing the dose may be linked to serious health risks. 

Phentermine has been associated with the rare yet serious condition known as pulmonary hypertension, which can result in fatal lung disease. Patients taking the medication should watch for symptoms like unexplained shortness of breath, chest pain, fainting, or leg swelling and seek immediate medical attention if they arise. The drug could raise the risk of heart valve disease, in which the heart’s valves don’t close properly and cause blood to flow backward.

Wegovy carries a boxed warning for thyroid cancer. It should be avoided in individuals with a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN 2). In addition, its use has been associated with pancreatitis, gallbladder disease, acute kidney injury, heart rate increases, and suicidal thoughts.

Wegovy and phentermine should be avoided in women who are pregnant due to the risk of harm to an unborn baby. These medications may also be present in breast milk, which may be harmful to a breastfeeding child. Consult a healthcare provider before taking these medications while pregnant or breastfeeding.