Think you're savvy about taking medication? Fifty percent of Americans aren't, according to studies. They don't take medicines correctly, stop them abruptly, or are unaware of what might go wrong when their prescriptions interact.

"It's a huge problem," said Katherine Tromp, a pharmacy professor at Lake Erie College of Pharmacy in Bradenton.

One of the most common mistakes is plain forgetfulness, said Tromp. People don't remember to take their pills or become confused when they can't recall whether they already took a dose on a particular day.

(Solution: Get a compartmentalized pillbox sold at drugstores or keep a running daily checklist. There also are lots of apps for smart phone alerts, said Tromp.)

As part of her teaching job, Tromp works three times a week in Bradenton drugstores, where she sees another frequent error. People drop off prescriptions but don't pick them up.

Some decide the drug is too expensive, said Tromp, or make up their minds the medicine isn't necessary.

OK, maybe this is something you wouldn't do. You always take the medicine your doctor prescribes down to the last dose. Although that's an absolute for being smart about medicine, there is still more to see to and some of it isn't obvious. Here are recommendations from pharmacists:

n Consult with the pharmacist before buying an over-the-counter drug.

Over-the-counters products can interfere with prescribed medications and cause unwanted side effects. Ask whether the product you want to buy can be taken safely with your medicines.

"This is something that people tend to forget about," said Tromp.

For example, generic Tagamet, an over-the-counter product for acid reflux, interacts with many medicines by slowing down how the prescribed drug is metabolized, she said.

Herbal products aren't off the hook. St. John's wort is one that interferes with a large number of medications, said Tromp. For people taking blood thinners, beware of herbal products such as gingko, garlic and ginseng that increase the risk of internal bleeding.

n Know the names of your prescriptions and the dosages.

"Don't just say it's a pink pill or a green pill," said Karen Halvorsen, a pharmacist who specializes in geriatrics and is a community educator for the Area Agency on Aging in Manatee and surrounding counties.

"It's really important to tell each of your practitioners about each prescription you are taking," she said.

Halvorsen recommends keeping an up-to-date list and taking it to every doctor's appointment. Include any over-the-counter medications and vitamins you are taking, too.

n Have your prescriptions filled at the same pharmacy.

Some people have their prescriptions filled at various drug stores depending on the cheapest price. While that's understandable, it isn't as safe as going to the same pharmacy.

By choosing one pharmacy, a record of all your prescriptions will be in the pharmacy's computer. The pharmacist will be able to spot problems such as potential drug interactions or when multiple doctors have unknowingly written different prescriptions for the same condition.

n Talk with your doctor before stopping a drug.

When a new drug is causing side effects, some patients just quit without calling their doctors. What they don't know is that another drug that treats the problem could be prescribed - if the doctor knew that the first medicine was causing discomfort.

"Lots of times, people get in trouble because they stop taking their medicine on their own," said Halvorsen.

Some medicines shouldn't be stopped abruptly, she said. For instance, stopping anti-acids without tapering doses could cause stomach acid to go sky-high through a rebound effect.

And, of course, potentially dangerous conditions such as high blood pressure and uncontrolled diabetes will go untreated when prescriptions are ignored.

n Be aware of how medicine can affect seniors.

A study of hospitalized seniors showed that one in 10 are admitted because of drug interactions, said Halvorsen.

Seniors are more likely to be taking multiple prescriptions and risk of interaction greatly increases when taking four or more drugs, she said.

Another factor that makes seniors susceptible is that their bodies aren't as effective in clearing medications. The drugs can linger instead of being flushed through the kidney and liver, resulting in too high levels.

And it can be easy to forget what a medicine is for, said Halverson. She recommends asking doctors to write the purpose of the medication on the prescription, such as "for arthritis." The pharmacist can include it on the pill bottle label.

Susan Hemmingway, Herald health correspondent, can be contacted at shemmingway@hotmail.com.