Prescription Weight Loss Drugs: How They Work

The popular medications Ozempic and Wegovy belong to the semaglutide family. There’s also the pill form called Rybelsus.

The FDA approved Ozempic and Rybelsus for use among people with type 2 diabetes in 2017, according to the FDA. Wegovy was approved in 2021 for those with obesity or overweight, as well as at least one weight-related condition (such as high blood pressure, type 2 diabetes, or high cholesterol). Wegovy’s approval was significant because it was the first weight loss medication approved by the FDA since 2014.

How Does Semaglutide Work?

“It’s a very effective drug,” Primack says. “It may be the most effective one we’ve had so far.”

It’s taken as an injection under the skin — usually the upper arm, thigh, or stomach — once a week, according to MedlinePlus. It belongs to a class of type 2 diabetes medications called glucagon-like peptide-1 agonists (GLP-1), which work by acting like the GLP-1 hormone in the body.

As blood sugar levels rise following a meal, this medication tells the body to increase insulin production to lower blood sugar levels, according to Mayo Clinic. The weight loss benefit appears to be a result of the drug decreasing appetite and slowing down the body’s digestive process, making those taking the medication less hungry (and ultimately eating less), according to UC Health.

There is also a pill form of the drug called Rybelsus. It’s currently available at a maximum dose of 14 milligram (mg), per the FDA, which Primack says, however, isn’t high enough to make it as effective as Ozemptic and Wegovy.

What Does the Research Say About Semaglutide?

A study published October 2022 in Nature Medicine found taking a semaglutide once a week for two years led to a 15.2 percent reduction in body weight versus 2.6 percent for the placebo, though the study participants did experience mild to moderate gastrointestinal issues. Those in the trial were overweight or obese and had one weight-related complication, but did not have diabetes.

Are There Side Effects of Taking Semaglutide?

“They have side effects, but they’re minor,” Primack says. Nausea, vomiting, and diarrhea are the most common; constipation is a less frequent one, according to a StatPearls review published in 2023. The common side effects can mostly be treated with over-the-counter medications, according to Primack.

There are other serious potential side effects, including pain in the upper stomach that may spread to the back, decreased urination, rash and swelling that make it hard to breathe or swallow, and a rapid heartbeat, according to MedlinePlus. Those experiencing these side effects should contact their doctor or healthcare provider right away.

And, thanks to the blockbuster status of these drugs (particularly Ozempic), consumers are reporting a range of other side effects they attribute to the weight loss medication, too, from burping to bloating to hair loss and more, according to Diabetes Daily, an Everyday Health Network site.

Is Semaglutide Covered by Insurance?

Generally, semaglutide is covered by insurance when treating a condition such as diabetes versus for weight loss, according to UC Health. Primack estimates that only about 10 percent of his patients who meet the FDA-outlined criteria are approved for Wegovy. Insurance coverage is important to consider as taking these medications without it can cost up to $15,000 a year.