(NEXSTAR) – A group of diabetes and obesity drugs are in such high demand that the Food and Drug Administration lists them as “currently in shortage.” People are seeking out the drugs to help shed pounds quickly, but short supply is making it hard for folks to get their hands on doses — whether they need it to treat diabetes or help lose weight.

So what happens if you stop taking them?

The drugs, semaglutide and tirzepatide, are better known by the brand names they’re marketed under: Ozempic, Wegovy and Mounjaro. They’re FDA-approved to treat diabetes and chronic obesity, but doctors also have the right to prescribe them off-label, and have been doing so for celebrities, influencers, and other willing to pay about $1,000 a month to lose weight.

Ozempic and Wegovy work by “mimicking a hormone … that targets areas of the brain that regulate appetite and food intake,” the FDA explains. Mounjaro activates that same hormone. Patients report lower appetites and feeling full faster.

All three are taken as weekly injections, and clinical trials showed they were effective at triggering significant weight loss.

But when the injections stop, much of the weight comes back, according to a study published in the Journal of the American Medical Association.

The study, published in 2021, looked at overweight and obese adults taking semaglutide for 20 weeks. Those who kept going after the 20-week period continued to lose weight, ultimately losing about 17% of their body mass on average over 68 weeks. Meanwhile, those who switched to a placebo at 20 weeks started to regain the weight they had lost, ending just 5% lower than where they had started.

Another study, published in August 2022, found that one year after participants stopped taking semaglutide, they regained two-thirds of the weight they had lost.

Weight gain can start to happen pretty immediately after you stop injecting Ozempic, or the other similar medications.

“I’ve seen people and they’ve lost maybe 50 pounds, and then they’re off of it for a month and then I see them back in clinic and they’ve gained 20 pounds,” Dr. Andrew Kraftson, a Michigan Medicine professor who specializes in obesity and metabolism, told The New York Times.

The study published in JAMA emphasized that obesity is a chronic condition, and therefore needs chronic treatment.

“Some people don’t have an awareness that this might have to be a medication that will be lifelong,” Dr. Alexandra Sowa, a doctor and NYU School of Medicine clinical instructor, told the Wall Street Journal.

“Like any medication, when you stop taking it, it stops working,” Dr. Robert Gabbay, chief scientific and medical officer of the American Diabetes Association, said in an interview with the Times.

The feelings of suppressed appetite will start to go away, and people will start to feel hungry much like they did before starting Ozempic, doctors explain. If you’ve lost a lot of weight quickly, you may feel even hungrier than before.

“When you’re at that max weight loss, your body’s hunger hormones are the highest,” Holly Lofton, who specializes in weight management at NYU Langone Health, told NBC News. “So if you lose 50 pounds and regain 25, your hunger is the highest when you’ve lost the 50. And even when you regain the 25, it doesn’t go back to baseline; your hunger is higher than prior to losing weight.”

Plus, since the drugs work to control blood sugar, going off the medication can lead to blood sugar spiking — a big problem for diabetics, Gabbay explained.

On the other hand, any negative side effects people experience while on the drug, like nausea, diarrhea, vomiting, constipation, abdominal pain and gastroesophageal reflux disease, should also go away once someone stops taking the medication.