What Are the Side Effects of New Weight Loss Medications?

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

Individuals have 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.

Interestingly, new research published in the journal Nature Medicine evaluated the health outcomes of more than 2 million veterans with diabetes taking a GLP-1 and found that while the medications had positive effects on several health conditions, like heart disease and substance use disorders, they were negatively associated with some, including arthritis.  

An increased risk of arthritis was not expected, says study co-author Ziyad Al-Aly, M.D., director of the Clinical Epidemiology Center at Washington University School of Medicine in St. Louis and chief of the Research and Education Service at the VA St. Louis Health Care System, since weight loss is generally considered beneficial for people with arthritis — especially if pain is in weight-bearing joints, like the hips and knees.  

However, Al-Aly says when people — and particularly older adults — lose weight, “they don't only lose fat; they actually lose muscle mass and bone mass,” which could help explain the association. Both bone loss and muscle loss are linked to joint problems, research shows.

The study also found that adults taking a GLP-1 had an increased risk for interstitial nephritis, a type of kidney condition that Al-Aly says is “almost like an allergic reaction that the kidney mounts against certain drugs.” He says more long-term studies are needed to better understand the risks and benefits of prolonged use.

Weigh the risks of side effects

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

A lot of people who experience the common side effects tend to feel better as they continue on the medications, not worse. Plus, intermittent treatments can bring relief. For example, an over-the-counter laxative like MiraLAX can help with constipation, Levy says.

Some of the side effects may not be a result of the drug but the weight loss itself — Levy says hair loss is “incredibly common” in people who lose a lot of weight — or they could be due to an underlying disease. Ozempic and Mounjaro are approved for diabetes, which 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 people with type 1 and type 2 diabetes.

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. Chetna Bakshi, M.D., a bariatric surgeon at Northwell Health’s Syosset Hospital in New York, says patients who have medullary thyroid cancer or a family history of it should not take them, because of the potential risk of thyroid C-cell tumors.  

Talk to your doctor

Bottom line: 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 the 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.

Some people take these medications without ever making a trip to see their doctor, new reports show. In 2023, the FDA warned consumers that semaglutide, the active ingredient in Ozempic and Wegovy, was being illegally marketed online. The agency warned 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.” 

Editor's note: This story, originally published Jan. 17, 2024, has been updated to reflect new information.