Many men who are taking ED drugs to enhance their sexual performance may be wasting their money. A new study from British researchers has found that the medications may only work for fewer than 50 percent of the men who take them.

The findings reinforce the notion that men that should look into other solutions to erectile dysfunction, such as constant resistance rings, before they start spending their money on expensive drugs.

Researchers said that many of the men who suffer from erectile dysfunction have low levels of testosterone, according to London’s Daily Mail. Due to the fact that ED drugs, in conjunction with testosterone, stimulate sexual arousal, men who have low levels of the hormone may receive no benefit.

Dr. Geoffrey Hackett, a urologist at Good Hope Hospital in Birmingham, told the news source that he didn’t find the results of the study particularly surprising.

“Viagra will only work if there are sufficient levels of testosterone,” he said. “Everybody thinks that Viagra is the panacea for all sexual problems, it’s not. If low testosterone is the problem then Viagra won’t be the answer on its own.”

As many as 2 million men may be taking ED medications, according to the National Institutes of Health.