(NEXSTAR) – Diabetes drugs Semaglutide and Tirzepatide – better known by the brand names they’re marketed under: Ozempic, Wegovy and Mounjaro – aren’t just being prescribed for diabetics anymore. They’ve become popular as celebrities, influencers and others willing to spend about $1,000 a month have used the medicines to lose weight quickly.

In many cases, it’s only possible for non-diabetics to get their hands on the drugs because doctors and other medical professionals are prescribing them “off-label.”

Off-label prescribing, the Food and Drug Administration explains, is when a health care provider writes a prescription for an FDA-approved drug, but for a use that is unapproved. It is a legal practice.

“From the FDA perspective, once the FDA approves a drug, healthcare providers generally may prescribe the drug for an unapproved use when they judge that it is medically appropriate for their patient,” says the FDA.

Mounjaro, for example, is only approved by the FDA to help type 2 diabetics control their blood sugar. Doctors can still prescribe it for non-diabetics as a weight loss tool, but that’s up to their discretion.

Wegovy, on the other hand, was FDA-approved for weight management in 2021. But here’s the catch: The FDA approved the weekly injection “for chronic weight management in adults with obesity or overweight with at least one weight-related condition (such as high blood pressure, type 2 diabetes, or high cholesterol).” Anyone who isn’t obese, or overweight with one of the named conditions, will need the doctor to prescribe it off-label.

It may or may not be covered by insurance, depending on your plan and conditions.

All three drugs have side effects, including nausea, diarrhea, vomiting, constipation, abdominal pain and gastroesophageal reflux disease.

Mounjaro has also been shown to develop thyroid tumors in rats. It’s not clear if the same would happen in humans, but the FDA advises against prescribing these drugs to those with a history of thyroid cancer in their family.