The over-the-counter painkiller you routinely take isn't harmless, and can lead to serious consequences, including liver failure and even death, says nationally renowned physician Erika Schwartz, author of "Don't Let Your Doctor Kill You."

You should take great care to keep close track of every single pill you take. "Whether you take a vitamin, painkiller, antibiotic, cough medicine, or supplement, it has the possibility to interact with other medicines you take, as well as what you eat or drink," Dr. Schwartz, CEO of Evolved Science, a concierge prevention medical practice, tells Newsmax Health.

When consulting with your doctor or other health professional, it is essential that you inform them of all medicines and supplements you take and work with them to make sure the total amounts are safe. Even then, you must educate yourself because many doctors aren't familiar with over-the-counter (OTC) drugs, and consider them harmless.

"That's simply not true," says Schwartz.

Most doctors know little about over-the-counter drugs, says Schwartz, and they often believe they are harmless and not powerful enough to cause a problem. So, often they pay little attention to the OTC drugs their patients are taking when writing prescriptions.

"This can lead to an overdose or other serious side effects, including liver and kidney damage," says Schwartz.

Many drugs that were available only by prescription in the past are now available over-the-counter with no health professional guiding their usage. In addition, due to the change in oversight by the federal government — from the Food and Drug Administration (FDA) to the Federal Trade Commission (FTC) — the way the drug is presented changes, says Schwartz.

A study published in the Journal of American Medicine found that the way drugs were presented to the public changed dramatically after they switched from prescription to OTC. Positive presentation rose from 83 to 97 percent while the presentation of negative effects dropped from 70 to 11 percent. In addition, warnings of side effects were allowed to be listed in small print on the label.

Some of the most dangerous examples of OTC drugs and combinations:

• Acetaminophen. A single regular Tylenol contains 325 mg of acetaminophen, and an extra-strength tablet contains 500 mg. For the average, healthy adult, the maximum recommended dose over a 24-hour period is 4 grams. Liver damage occurs at 7 grams.

"Most people take two or three at a time," says Schwartz. "If you take three pills five times a day, you're already over the safe dosage limit with the regular tablets, and into the possibility of liver damage with the extra-strength pills."

It can be very easy to overdose on acetaminophen because it's contained in many OTC products, including cold and flu treatments. Combining medications, such as acetaminophen tablets with cough syrups and cold medicines that also contain the painkiller, can quickly put you in the danger zone. Always read labels.

"In addition, many common prescription pain relievers contain acetaminophen, including Vicodin and Fioricet," says Schwartz. "When people take the prescription drug and Tylenol together, they're getting too much acetaminophen."

• Laxatives (sodium phosphate). These drugs, which include the Fleet brand, are used to treat constipation and should not be used more than once a day for no longer than three days, she says. "It's very easy to get too much of these types of medicines, and they can  cause dehydration even at recommended doses which can lead to kidney damage."

According to the FDA, a single dose higher than recommended or more than one dose in a day can cause serious harm. Adults over 55 years of age, young children, and patients using other medications are more at risk of kidney damage.

• Cough and cold medicines. Dextromethorphan is a common ingredient in cough medicines, but it can be deadly if taken in higher than recommended amounts, says Schwartz. Dextromethorphan is found in Robitussin, PediaCare, and many other cough suppressants. It can lead to impaired judgment, dizziness, loss of coordination, nausea and vomiting, respiratory depression, coma, and death.

During cold and flu season beware of taking several different OTC medications that contain the same ingredient. "Advil, Aleve, Motrin, Advil Cold & Sinus, and Motrin IB all contain ibuprofen, while Tylenol, Pamprin, and Tylenol Cold contain acetaminophen," says Schwartz. "You can easily overdose and not know it."

• Aspirin. After being recommended many years by health professionals to prevent heart and stroke, The National Institutes of Health issued a warning to doctors advising them to reconsider routinely recommending patients take aspirin daily. "Taking a daily aspirin, even at the low dose of a baby aspirin, can cause bleeding in the gastrointestinal tract," says Schwartz. "It can even cause bleeding in the brain of vulnerable patients."

• Mixing Tylenol and Advil. Doctors frequently recommend patients take a dose of acetaminophen followed by a dose of ibuprofen two hours later, then repeat the cycle. This treatment can be overwhelming for some people, especially children whose systems are more vulnerable, says Schwartz.

"Just because a drug is sold over the counter doesn't mean it is harmless," says Schwartz. "Patients believe these drugs are safe, but they can be deadly."