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Taking Your Vitamins? Make Sure To Tell Your Doctor


You exercise regularly and eat healthy foods. And to boost your immune system, you take a multivitamin every day. It can only help, right? Well, perhaps.

A recent study published in The New England Journal of Medicine found that adverse effects of supplements were responsible for an average of about 23,000 emergency department visits per year.

Still, American consumers spend billions of dollars on vitamins, herbs, minerals and supplements. National health surveys show that more than half of all American adults take some kind of vitamin or dietary supplement, a percentage that increases with age.

Many people don’t realize that taking some over-the-counter supplements alongside prescription drugs and other medicines can have dangerous and even life-threatening effects, according to Brittany Langdon, PharmD, a pharmacist and manager of the Apothecary and Wellness Center at Yale New Haven Hospital. That’s why it’s important to talk to your physician about everything you are taking.

“A number of supplements can enhance, diminish or negate a prescription drug in ways that can be consequential and unpredictable,” she said. “Many supplements can contain ineffective or harmful ingredients, especially if combined with prescription drugs.

According to Langdon, supplements and vitamins can change the “ADME" of your prescription medications. ADME stands for absorption, distribution, metabolism and excretion of drugs. Depending on the person and the drug they are taking, interactions can be serious. Vitamins and supplements can cause harmful reactions, or they may reduce the effectiveness of prescription meds.

For example, warfarin is a drug often prescribed to treat or prevent blood clots in veins or arteries. Gingko biloba (an herb) and vitamin E supplements can thin your blood – so taking them with warfarin potentially increases your risk for internal bleeding or stroke. Vitamin C is often consumed as a supplement to ward off the common cold —but high-dose vitamin C supplements may reduce the effectiveness of some types of cancer chemotherapy and interfere with statin medications.

Langdon says that many people also think that because a vitamin or supplement is advertised as “natural” it means the product is “safe.” This can be a dangerous assumption.

“Vitamins and supplements are regulated as foods, not drugs. This means the Food and Drug Administration does not evaluate the quality of the supplement or assess its effect on the body before the product hits the shelves,” she said. “Some supplements can have a range of ingredients instead of exactly the amounts listed on the labels – which is why, even though supplements are ‘natural,’ they can sometimes be unsafe.”

To help avoid any health hazards that can arise from mixing supplements and medications, Langdon recommends that you:

  • Talk to your doctor before starting any new over-the-counter medication or supplement. “If you feel you need something else in your diet, your doctor can make sure there aren’t any underlying conditions that may be the reason you feel the need to supplement,” she said.
  • Update your medication information. Bring a list of everything you take — over-the-counter medicines (pain pills, allergy relief, etc.), herbals, minerals, vitamins, dietary supplements and prescription drugs — to your next doctor’s appointment.
  • Keep track of the dosages and how many times a day you take them.

Also, if you’re planning a surgery, don’t be surprised if your doctor asks you to stop taking dietary supplements two or three weeks before the procedure to avoid changes in heart rate, blood pressure or bleeding risk.