(NewsNation) — Medical professionals in the weight loss field are issuing a warning after reports of two deaths linked to fake weight loss medication.

One of the drugs, Ozempic, is designed to treat diabetes but has also shown progress in helping some people lose weight. The high demand and cost, however, have deterred many from accessing the medication. Some have resorted to trying to find cheaper alternatives.

The U.S. Food and Drug Administration (FDA) is investigating reports of two deaths and dozens of health complications after people allegedly took fake weight loss medication. According to the FDA, there have been 28 reports of adverse effects from counterfeit semaglutide in the U.S. It’s an even bigger issue in the United Kingdom, where officials have seized more than 300 fake injectables.

Dr. Sue Decotiis, a medical weight loss physician in New York, told NewsNation she’s not surprised by the news.

“I think online platforms are dangerous,” Decotiis said of buying these medications over the internet. “Because even if you’re getting the right medication, you’re not being monitored. No one is following your weight. As far as your body composition, like how much fat are you losing? Are you losing muscle?”

She said that even in cases where professionals closely monitor patients, dehydration is still a cause of concern.

“When you’re burning fat rapidly, you can become very dehydrated. And if you’re dehydrated, the symptoms, the side effects of these drugs — especially in the first month or two of treatment could be severe,” Decotiis said.

Decotiis advises patients under her care to drink “about a gallon” of water daily while on weight loss medication.