What To Know About Mounjaro

Photo: Sandy Huffaker for The Washington Post via Getty Images

While Ozempic has surged in popularity this year, there’s another diabetes drug and weight loss agent on the rise. Mounjaro, also known by its generic name tirzepatide, hit the market in May 2022 as a prescription injectable to regulate the blood sugar of people with type 2 diabetes. But it quickly garnered mainstream interest for its secondary outcome: helping patients lose weight more effectively than Ozempic or Wegovy. The drug’s boom in popularity has led to monthslong shortages, making it harder to access for patients who need it.

Dr. Reshmi Srinath, a New York–based endocrinologist and the director of obesity medicine at Mount Sinai, says the volume of patients — both diabetics and those worried about becoming diabetic — coming into the hospital’s Upper East Side campus has “exponentially grown” in recent months. “I appreciate that patients are more aware of their weight and lifestyle and there’s a greater emphasis on trying to be healthy,” says Dr. Srinath. But at the same time, “We have to be careful about utilizing these medications, which can be very potent and aggressive. None of these are magic pills.” Pending ongoing clinical trials, Mounjaro may soon receive FDA approval for weight loss, but until then Dr. Srinath doesn’t recommend off-label use. 

What is Mounjaro?

Wegovy, Ozempic, and Mounjaro all promote weight loss by decreasing appetite. But while Ozempic and Wegovy, known as semaglutides, work on one hormone — glucagon peptide 1, or GLP 1, which comes from the small intestine and regulates blood sugar and appetite — Mounjaro (or tirzepatide) is unique in that it works on both GLP-1 and a second hormone, gastric-inhibitory polypeptide, or GIP, which secretes insulin. “There’s sort of a synergy between these two hormones in the gut,” says Dr. Srinath, which leads to improved blood sugar and more effective weight loss. The FDA reported that patients on Mounjaro lost an average of 12 pounds more than those taking Ozempic or Wegovy. That said, it doesn’t work for everyone, and Dr. Srinath has patients who don’t respond to it all.

What are Mounjaro’s side effects?

Dr. Rocio Salas-Whalen, an endocrinologist and obesity specialist at New York Endocrinology considers Mounarjo to be the “new and improved” drug of the trifecta, with next to none of gastrointestinal side effects of Ozempic or Wegovy. She says Mounjaro’s muted side effects make it ideal for patients who can’t tolerate the gastrointestinal upset of semaglutides and therefore can’t progress to higher doses of those drugs. “With Ozempic and Wegovy, we see more nausea, reflux, constipation,” says Dr. Salas Whalen.

If a patient does experience side effects from Mounjaro, the most common ones are gastrointestinal, similar to Ozempic, Dr. Srinath says. “Both work to slow the way food moves through the gut so you feel fuller quicker. But this can also contribute to acid reflux, bloating, constipation,” she says, along with nausea, decreased appetite, bloating, flatulence, and abdominal pain. Like Ozempic, there’s also the possibility of severe but rare side effects with Mounjaro, like an increased risk of thyroid cancers.

Are there risks to taking Mounjaro off-label?

Though there’s little data about how Mounjaro impacts those who take it off-label, Dr. Srinath says using it without proper medical supervision can be risky. “It is extremely important that patients get the FDA-approved version of these drugs and use them for their approved indication,” says Dr. Srinath, who’s had “a few cases” where patients have obtained some form of semaglutide, either online or through a private clinic, and experienced “severe side effects” as a result, including a number of young patients who ended up in an emergency room with extreme nausea and abdominal pain after taking improperly titrated doses. “Those symptoms can last for a long time, and they impacted their appetite and quality of life,” she says.

Those on Mounjaro have to be monitored closely, since taking the drug unsupervised can lead not only to increased gastrointestinal side effects, but to weight regain when not tapered off correctly. “These medications aren’t something you can start and stop,” says Dr. Srinath. “There’s growing data that steady weight loss — one to two pounds a week — is appropriate.” Lose weight too quickly and aggressively, and you could gain back more weight after going off the drug, what Dr. Srinath calls a “yo-yo effect.”

How is off-label use of Mounjaro affecting diabetes patients?

Pharmaceutical companies are struggling to keep up with the growing demand for diabetes injectables, leading to supply issues for those who need the medication to regulate their blood sugar. “There have been a lot of shortages, which have been frustrating to patients on Ozempic as well as other medications,” says Dr. Srinath, who has had patients start on the lowest dose of Mounjaro only to get calls from the pharmacy saying they don’t have the next two doses in stock, sending patients on a wild goose chase to find pharmacies that do.

Even amid efforts to ensure the drug is reserved for those with diabetes — Eli Lilly has restricted their savings program, which helps patients secure injections at a substantial discount, to type 2 diabetics only — Dr. Srinath has patients who don’t get their medicines for weeks because of shortages: “During these times, they have experienced greater appetite and some of the side effects they were feeling good about — weight loss, appetite suppression — went away, and their blood sugars were out of control. Definitely the shortages have significantly impacted them.” 

Meanwhile, many patients with weight-related conditions who saw improvement on Mounjaro are frustrated that the medication has become inaccessible and unaffordable with the changes to the manufacturer’s savings coupon. The drug is roughly $1,000 a month out of pocket, comparable to out-of-pocket costs for Ozempic and Wegovy. Doctors in obesity management are also frustrated by the restrictions. “We offer something great for the patients at a very low cost, and then suddenly we have to transition everybody back to Wegovy or Ozempic,” says Dr. Salas-Whalen.

Following a two-month long shortage, Eli Lilly announced last month that the Mounjaro was back in stock, though they noted that its “dynamic demand” may still cause some pharmacies “to experience intermittent delays from time to time.” For her part, Dr. Salas-Whalen is hopeful about the FDA approval of Mounjaro for weight-loss. “There will be no more competition,” she says. “Diabetics will have Mounjaro and people with obesity will have theirs.”

What to Know About Mounjaro