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What Are the Side Effects of New Weight Loss Medications?

Common reactions to popular drugs like Ozempic and Wegovy can range from nausea to stomach pain


spinner image close up of a pharmacist holding a box of Wegovy weight loss medication
A pharmacist holds a box of Novo Nordisk A/S Wegovy brand semaglutide medication arranged at a pharmacy in Provo, Utah, US, on Monday, Nov. 27, 2023. Prescriptions of appetite suppressing GLP-1 weight-loss drugs skyrocketed 300% from 2020 to 2022.
George Frey/Bloomberg via Getty Images

It’s hard to turn on the TV, read the news or make it through a conversation without hearing about Ozempic and other drugs like it that belong to a class of medications known as glucagon-like peptide 1 (GLP-1) agonists.

These drugs — some federally approved for diabetes, some approved for weight management — have shot to superstar status for their weight loss effects. In some cases, they are helping people shed about 20 percent of their body weight.

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It’s no wonder, then, that demand for them is through the roof. A recent poll from the University of Michigan found that more than 60 percent of overweight adults ages 50 to 80 are interested in taking one.

“These are game-changing medications,” says Shauna Levy, M.D., an obesity medicine physician at the Tulane University Medical Center and medical director of Tulane’s Bariatric and Weight Loss Center.

But like any drug, they are not without side effects. Read on to learn more about the common — and rare — side effects of these newer weight loss medications, and what the latest research shows.

Common side effects of drugs used for weight loss  

Four of the more popular GLP-1 medications — Ozempic and Mounjaro (approved for diabetes) and Wegovy and Zepbound (approved for weight loss) — have similar side effects.  

The most common side effects include:

  • Nausea
  • Diarrhea
  • Vomiting
  • Constipation
  • Stomach pain

However, other, more serious, issues have also been linked to these drugs, including gallbladder problems, low blood sugar, kidney injury and diabetic retinopathy (damage to the eye’s retina).

A 2023 study published in the medical journal JAMA found that people who take these medications may be at increased risk for pancreatitis (inflammation of the pancreas) and gastroparesis, sometimes called stomach paralysis because the stomach can’t empty.

Individuals have also reported hair loss when taking these drugs, as well as aspiration (when food or liquid enters the airway) when sedated for surgery, likely due to the delay in stomach emptying caused by the drugs.

Suicidal ideations have been associated with these medications; however, in recent studies, researchers found no clear relationship.

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Meds may lessen cravings, improve heart health

Not all of the reported side effects of these GLP-1 medications are bad, though. Some patients taking the drugs say many of their former cravings — be it alcohol, shopping or sugar — have subsided. 

“Cravings develop from a reward system in the brain,” says Chetna Bakshi, M.D., a bariatric surgeon at Northwell Health’s Syosset Hospital in New York. These medications, she says, seem to have an effect on that reward system. “I have had patients tell me, for example, ‘I used to crave sweets all the time. Now I don’t care. I don’t need to eat a cookie every day being on these medications,’ ” Bakshi says.

“That’s the biggest thing of how these medications work,” Levy adds. “They quiet the noise in your brain.”

Another positive effect: In a large clinical trial, researchers found that semaglutide, the active ingredient in Ozempic and Wegovy, can reduce the risk of heart attacks and strokes by 20 percent in adults with heart disease and obesity. The study was published in December 2023 in The New England Journal of Medicine.

And a new study, published Feb. 5 in Hypertension, found that tirzepatide, the active ingredient in Mounjaro and Zepbound, significantly lowered the systolic blood pressure (the top number in a blood pressure reading) of nearly 500 adults who had obesity and took the medication for about eight months. The reduction ranged from an average of 7.4 mm Hg to an average of 10.6 mm Hg, depending on the dose of medication. 

“Although tirzepatide has been studied as a weight loss medication, the blood pressure reduction in our patients in this study was impressive. While it is not known if the impact on blood pressure was due to the medication or the participants’ weight loss, the lower blood pressure measures seen with tirzepatide rivaled what is seen for many hypertension medications,” lead study author James A. de Lemos, M.D., a professor of medicine at UT Southwestern Medical Center in Dallas, said in a news release. 

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Weigh the risks of side effects 

Despite reports of some of the more serious side effects, Levy says these medications have a pretty solid safety record. (Some of the GLP-1 agonists have been around for nearly two decades.)

With the common side effects, a lot of people tend to feel better as they continue on the medications, not worse. Plus, there are intermittent treatments that can bring relief. For example, MiraLAX can help with constipation, Levy says.

Does Insurance Cover Weight Loss Drugs?

That depends on what insurance you have and why the medication was prescribed. For example, Medicare Part D will cover GLP-1 medications for diabetes treatment for patients with diabetes. However, the program will not cover medications for weight loss. If you have private insurance, coverage will vary by plan. Without insurance coverage, the popular GLP-1 agonists can cost upwards of $1,300 per month.

Some of the side effects may be a result of not the drug but the weight loss itself — like hair loss, which Levy says is “incredibly common” when you lose a lot of weight — or even underlying disease. Ozempic and Mounjaro are approved for diabetes, for example, and diabetes is the most common known cause of gastroparesis (stomach paralysis), according to the National Institute of Diabetes and Digestive and Kidney Diseases. In some studies, it affects up to half of the population with type 1 and type 2 diabetes.

Still, these diabetes and weight loss medications are not for everyone. People who have a history of pancreatitis should discuss the risks with their doctor before starting the drugs. And Bakshi says patients who have medullary thyroid cancer or a family history of it should not take them, due to the potential risk of thyroid C-cell tumors. 

What’s more, research suggests that most people regain much of the weight they lost when they stop taking the medications. One study, published in the journal Diabetes, Obesity and Metabolism, found that participants gained back two-thirds of the weight they lost a year after stopping Wegovy. 

Talk to your doctor

Bottom line, health experts say: Have a conversation with your health care provider before starting these medications. “Side effects are always important to know, and [patients should] understand that there’s no miracle drug,” Bakshi says. “Everything comes with a risk; everything comes with complications.”  

Reports of aspiration underline the need for medical supervision while taking these medications, Levy says. The American Society of Anesthesiologists suggests withholding GLP-1 medications before elective surgery to reduce the risk of complications, and this is something your doctor can help with, should you have an upcoming operation.

But some people are taking these medications without ever making a trip to see their doctor, new reports show. The Food and Drug Administration (FDA) says semaglutide, the active ingredient in Ozempic and Wegovy, is being illegally marketed online. The agency warns that “these drugs may be counterfeit, which means they could contain the wrong ingredients, contain too little, too much or no active ingredient at all, or contain other harmful ingredients.”

“It could certainly lead to complications if patients are not being screened properly and counseled properly,” Levy says. “So I think that’s the big takeaway.”

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