How does Wegovy work?

If you struggle with managing your weight, you may be interested in prescription options that help with long-term weight loss. Wegovy, a weight loss shot administered once a week, is one option you can consider. 

What is Wegovy?

Wegovy (semaglutide; see Important Safety Information) is a prescription drug that helps with chronic weight management when combined with exercise and a low-calorie diet. It’s recommended for people with obesity (defined as having a BMI of 30 or higher) or those who have overweight (with a BMI of 27 or higher) along with a weight-related health condition, such as type 2 diabetes, high blood pressure, or high cholesterol (Phillips, 2022; FDA, 2021). 

The prescription pen comes pre-filled with a single dose of Wegovy, which you inject subcutaneously (under the skin) in your abdomen, upper arm, or thigh using the attached needle on the pen. Wegovy injections should be done once a week, around the same time of day, either with or without meals. It comes in five doses: 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, and 2.4 mg. When not in use, You should store Wegovy medication in your refrigerator (FDA, 2021; Phillips, 2022).

How does Wegovy for weight loss work?

Wegovy shares the same active ingredient—semaglutide—as some other GLP-1 receptor agonists. Semaglutide mimics GLP-1, a hormone that regulates your appetite. Weight loss drugs like Wegovy reduce your appetite and slow digestion. When digestion slows down, it takes longer for your stomach to fully empty, helping you feel full longer. So, you may ingest less food and experience weight loss while using Wegovy (Phillips, 2022; Singh, 2022). 

It is also possible that GLP-1 receptor agonists like Wegovy affect how your brain’s reward center reacts to food. This interaction may affect your appetite and lead to weight loss (Singh, 2022). 

How long does it take to lose weight on Wegovy?

In one study, people with obesity were split into two groups. One group took a placebo, while the other took semaglutide (the active drug in Wegovy) once a week. After 68 weeks (about a year and four months), the participants taking semaglutide lost nearly 15% of their body weight on average, compared to less than 3% in the placebo group (Wilding, 2021). 

In addition to losing a significant amount of weight, those taking semaglutide also experienced other improvements in their cardiometabolic health and reported better physical functioning (Wilding, 2021).

Although all GLP-1 medications (typically prescribed to treat diabetes) can lead to weight loss, research suggests Wegovy may be more effective than other drugs at reducing body weight in people with a combination of type 2 diabetes and overweight or obesity (Singh, 2022). 

Does Wegovy have any side effects?

Wegovy’s side effects are typically gastrointestinal and range from mild to moderate. Nausea, diarrhea, vomiting, and constipation are the most common side effects, usually lessening over time as you continue using the drug (Singh, 2022; Wilding, 2021). Additional side effects of Wegovy may include (FDA, 2021):

• Abdominal pain

• Headache

• Fatigue

• Indigestion

• Dizziness

• Bloating

• Burping

• Flatulence

• Gastroesophageal reflux disease (GERD)

Severe side effects of Wegovy may include allergic reactions, suicidal thoughts, gallbladder disorders, pancreatitis (swelling of the pancreas), kidney failure, increased heart rate, and, in people with type 2 diabetes, hypoglycemia (low blood sugar) or diabetic retinopathy (vision loss or changes) (FDA, 2021; Wilding, 2021).

The US Food and Drug Administration (FDA) has issued a black box warning for Wegovy. Animal studies have found that semaglutide increases the risk of thyroid tumors in rodents. While it is not known if it has the same effect in humans, Wegovy should not be used by people with multiple endocrine neoplasia syndrome type 2 or with a personal or family history of thyroid cancer (FDA, 2021).

Wegovy is not for everybody. Experts still don’t know whether it is safe to use other weight loss products or supplements while taking Wegovy, so your healthcare provider may recommend against using those. Also, Wegovy should not be used with other glucagon-like peptide-1 (GLP-1) receptor agonists, such as Ozempic (see Important Safety Information) or Rybelsus. Finally, Wegovy is not recommended for people who (FDA, 2021; Phillips, 2022):

• Have a history of pancreatitis

• Are pregnant

• Have a personal or family history of medullary thyroid carcinoma

Before using Wegovy, tell your healthcare provider about your personal and family medical history and any medications you are currently taking.

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

August 04, 2022

Written by

Amelia Willson

Fact checked by

Chimene Richa, MD

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About the medical reviewer

Chimene Richa, MD

Dr. Richa is a board-certified Ophthalmologist and medical writer for Ro.