Hair thinning, nail problems and rare eyesight risks: What to know about GLP-1 medications

Multiple studies have shown that the weight-loss drugs known as GLP-1s, including Wegovy and Zepbound, can lead to significant weight reduction, better blood sugar control and, depending on the medication and the patient, improved heart health or relief from sleep apnea.

More recent research has also pointed to possible side effects such as hair loss, changes in the nails and, in rare instances, sudden vision loss. Scientists do not understand all of these risks equally well, and the seriousness of the effects can differ. Even so, doctors and researchers say the advantages of GLP-1 drugs usually outweigh the harms for most people.

“Any medication could have side effects,” said Disha Narang, a physician and director of obesity medicine at Endeavor Health. But with GLP-1s, “We actually see much more benefit than risk.”

Do GLP-1s cause vision loss?

The most concerning issue has been a possible link between GLP-1 use and nonarteritic anterior ischemic optic neuropathy, or NAION, a condition sometimes described as an “eye stroke” because it can trigger sudden and permanent vision loss.

The condition appears to be uncommon.

In one recent study, there were three or four more NAION cases per 10,000 patients taking GLP-1 drugs than among those not using them, said Chintan Dave, an associate professor of pharmacy and epidemiology at Rutgers University and the study’s senior author.

Using insurance records, researchers compared adults with Type 2 diabetes who began GLP-1 treatment with those starting other diabetes medications. Over an 18-month period, Dave and his team estimated about eight NAION cases per 10,000 GLP-1 users, compared with four to six per 10,000 among patients on the other drugs. Because the study was observational, it did not prove that GLP-1 medications directly caused the higher risk.

“In terms of perspective, it’s extremely rare,” said Dave, who also directs the Center for Health Outcomes, Policy and Economics at Rutgers. Still, he said patients should know the warning signs and seek immediate care for sudden, painless vision loss.

Hair and nail loss

Hair loss appears to be a more common side effect. Across several randomized controlled trials, about 3% to 6% of patients taking Wegovy and Zepbound reported hair loss, compared with 1% of people on placebo.

It also seems more common among women. In Zepbound studies, 7.1% of women and 0.5% of men reported hair loss, compared with 1.3% of women and no men in the placebo group.

A study published in The BMJ also found a higher rate of hair loss among adults with Type 2 diabetes who started GLP-1 medications than among those taking other diabetes drugs. Researchers said the absolute risk was low and that more study is needed to explain the connection.

Early research has also suggested a possible relationship between GLP-1 use and weaker nail health. At the European Academy of Dermatology and Venereology Congress, researchers compared 575 GLP-1 users with 1,329 nonusers who had obesity, Type 2 diabetes or both. Among those taking a GLP-1 drug, 39% said their nails separated from the nail bed, compared with 9% of nonusers. The study did not determine how often the medications caused new nail problems, and about half of participants reported nail issues before starting treatment. The symptoms were self-reported.

Narang noted that major weight loss, whether or not it comes from medication, can affect hair growth and nail quality.

“If you lose a significant amount of weight, you’re gonna have changes in your hair growth and or nail quality,” she said. “So it’s not a side effect of the medication per se.”

Less food intake, whether from a deliberate diet or reduced appetite caused by a GLP-1, can leave patients short on protein and other nutrients. When patients mention hair or nail changes, she looks at whether they are eating enough and meeting nutritional needs. In many cases, hair loss is temporary and can reverse.

Long-term outlook

Although they have only recently become widely known, GLP-1 medications have been used to treat diabetes since the early 2000s.

“These are not new medications,” Narang said. “We have a good two decades of experience with GLP-1 agonists.”

Some of the newer drugs, and their use specifically for weight loss, have a shorter history. The U.S. Food and Drug Administration approved Ozempic for Type 2 diabetes in 2017, while Wegovy and Zepbound were approved for weight management in 2021 and 2023. Studies have tracked patients for several years, but researchers still do not have two decades of data on long-term obesity treatment with these newer medications.

Nausea, vomiting, diarrhea and constipation are among the most common side effects. Narang said patients often tolerate the drugs better if they start at a low dose and increase slowly. If symptoms continue, staying at a lower dose longer may help.

“There’s definitely no race to the top dose,” she said.

She also recommends smaller meals, avoiding rich or greasy foods that can worsen symptoms, and making sure to get enough fluids and fiber.

Even with the known and emerging side effects, Dave said the benefits remain considerable.

“We don’t have a lot of amazing therapies for weight loss that are also really good for your heart, kidneys and metabolic health,” Dave said. “I really think that currently the benefits by far outweigh the risk.”