On a quest to be young again, some people will do anything. They’ll even pump the blood from a younger person into their body in the hopes of shaving off a few years. The FDA has one simple warning: stop!

In a statement by the agency this week, the FDA stated that the plasma from a younger person offers “no proven clinical benefit” as a treatment against aging or diseases. This report comes as some establishments in several U.S. states have been offering infusions of plasma from young donors to treat a variety of conditions, ranging from “normal aging and memory loss to serious diseases like dementia, Parkinson’s disease, multiple sclerosis, Alzheimer’s disease, heart disease or post-traumatic stress disorder.”

There are 14.6 million blood transfusions a year, according to the Centers for Disease Control and Prevention. Plasma, the liquid portion of the blood, is used every day to treat emergency trauma, cancer and other conditions and diseases. So why not aging? The FDA warned, “Today, we’re alerting consumers and health care providers that treatments using plasma from young donors have not gone through the rigorous testing that the FDA normally requires in order to confirm the therapeutic benefit of a product and to ensure its safety,” said the FDA. “As a result, the reported uses of these products should not be assumed to be safe or effective. We strongly discourage consumers from pursing this therapy outside of clinical trials under appropriate institutional review board and regulatory oversight.”

Blood transfusions seem to be all the rage among individuals that can pony up the upwards of $8,000 it costs to get the transfusion at these “young blood” clinics. The transfusion was even portrayed in an episode of HBO’s Silicon Valley, aptly named “The Blood Boy,” when billionaire Gavin Belson is openly getting a blood transfusion from a younger man in the hopes of reinvigorating himself.

The theory of young blood is not a new one. It has been floating around since the 1860s when physiologist Paul Bert was studying the circulatory system. It continued later into the 1930s when Cornell University biochemist and gerontologist Clive McCay conducted some of the first experiments on taking the blood from younger rats and infusing it into older ones. A report out of the University of California of Berkeley even found that these transfusions helped repair and regenerate aging muscles in mice. 

Some people will do just about anything to be younger, but these blood transfusions may not be the best route until more research comes in—maybe stick to the creams, healthier diet, and exercise. After all, there’s no solid evidence proving that young blood will reverse those signs of time.