It doesn't take long to find ads on the internet for erectile dysfunction, or ED drugs.

And with a few clicks and a credit card, you can get the drugs delivered to your door.

But a new medical paper is warning people to be cautious.

"There are some huge caveats or limitations that we need to be aware of," says Dr. Ajay Nehra from the Mayo Clinic.

Drugs like Viagra, Levitra and Cialis may improve symptoms of ED but they do not treat the possible underlying conditions that may be causing it, like diabetes, high blood pressure and Parkinson's disease.

"And in a small percentage of patients, the onset of sexual dysfunction may indeed by the initial manifestation of quiet but definite coronary artery disease," says Dr. Nehra.

Some medications used for depression or high blood pressure can also affect your sexual health.

Sometimes a simple dosage change by your doctor is all that is needed to fix the problem. That's why men interested in taking these drugs should see their doctor first.

Not only to look for other health problems, but to make sure they're not setting themselves up for heart and health problems.

"We want consumers to understand that they simply should be self-prescribing for themselves over the internet. They really should have good check up done," he says.

Good advice for any prescription medication.

With a report from CTV British Columbia's Dr. Rhonda Low