Medical cannabis is legal in more than half of U.S. states, but it still remains illegal under federal law. The Food and Drug Administration does not in fact regulate derivatives of the plant, such as CBD extracts.

CBD is one of the active ingredients in cannabis that is widely thought to offer a wide range of health benefits.

“More and more evidence is coming out that CBD can be helpful for a variety of conditions, from anxiety to inflammation to seizures and epilepsy,” Marcel Bonn-Miller, an adjunct professor of psychology in psychiatry at the University of Pennsylvania, said.

Bonn-Miller said products were supposed to go through a “systematic evaluation” to let consumers know what they were buying. Today, “It’s the Wild West,” he said.

To find out the labeling accuracy of CBD extracts sold online, Bonn-Miller and his team brought 84 commercially available CBD products on the internet, including oils, tinctures (alcoholic extracts), and vaporization liquids and had them analyzed by an independent lab for a study published recently in the Journal of the American Medical Association.

Only 31 percent of the products tested contained the precise amount of CBD advertised on the label, while 26 percent contained less CBD than the label indicated and 43 percent contained more.

Product type mattered in the accuracy of labeling as well. About half of the CBD extract oils were labeled inaccurately; nearly 90 percent of the vaporization liquids were labeled inaccurately, and tinctures were equally likely to be over, under or accurately labeled.

Bonn-Miller was neither shocked nor disappointed at the results.

“It just got me thinking, we need oversight of this industry…(It’s) one thing on the recreational side, but here we’re talking about something that people are using almost exclusively medicinally. You don’t get high off of CBD.”

Another finding in the study pointed out the concentration of unlabeled cannabinoids was generally low, but THC was detected in 18 of the 84 samples tested.” According to Bonn-Miller, THC, or tetrahydrocannabinol, is psychoactive and could cause trouble sleeping and cognitive impairment if ingested unknowingly.

CNN Chief Medical Correspondent Dr. Sanjay Gupta said the supplement industry overall is not regulated.

“You don’t always know what you’re getting, how much you’re getting or even if the active ingredients are in there at all. With medical marijuana, it is almost the opposite situation at the federal level. It is highly regulated,” Gupta said.

Bonn-Miller is hoping his study will prompt changes in regulations.

“If the FDA regulated this industry, we would be way better off,” he said. “They’re good at regulating things. When you go and buy a prescription at a pharmacy, you know what you’re getting… (It’s the) same thing for food. When you get a pack of Doritos or a Hershey bar, you know that it is.”

Last week, the FDA issued warning letters to four companies, which were claiming their online products prevented, treated or cured cancer without evidence to support their statements.

Until these products are officially regulated, Bonn-Miller suggests users should be careful with the dosage, but also talk to their doctors before starting or stopping any medication or supplement, including CBD.