Doctors are warning people heartburn treatments in combination with other drugs can be dangerous.

The Canadian Association of Gastroenterology says consumers should be aware interactions can occur.

Dr. Peter Lin of University of Toronto's Health and Wellness Centre says over-the-counter treatments are so common many people don't think to tell their doctors.

"Some drugs require acid in your stomach to be absorbed," says Lin.

"If we're taking lots and lots of antacids then medications would not be absorbed as well."

Lin's patient Carl Herman learned the hard way. Herman is one of 10 million people in Canada who get heartburn.

"I was taking Rolaids all the time or whatever medication I could get my hands on, the over-the-counter chewable things," says Herman.

The pain became unbearable and Herman went to see Dr. Lin.

He was amazed to find out those chewable pills could combine with other medications he was taking to cause side effects.

"That was something I never thought about until I went to my doctor."

Lin says advances in medicine mean people are taking more medications than ever.

He warns some prescription heartburn drugs can also knock out enzymes that help metabolize other drugs. That means other medications can accumulate in the body.

"The medication that doesn't leave because the path is blocked would then build up. And so if you happen to head into the toxic amount you might get the toxic side effect," says Lin.

The only way to prevent dangerous interactions is to tell your doctor about every medicine or herbal remedy you take.