If you take vitamin supplements while on certain medications, take note of possible risks of drug interactions. Drug interactions occur when a medication is combined with another substance, changing the medication's effect on your body and possibly causing harm.
A drug interaction can occur between any two or more types of drugs, including prescription medicines, over-the-counter medications, vitamin supplements, herbs and teas. There are two main ways supplement and medication interactions can affect you:
- The supplement increases or decreases the potency of the medication
- The reaction between the supplement and medication can cause harmful side effects
One example of an interaction is the use of American ginseng while taking a blood thinner such as warfarin (Coumadin). "If you've been taking ginseng over a period of time while on warfarin, ginseng may decrease the blood thinner's effectiveness and increase your risk of a clot," says Dr. David Hall, a double board-certified internal medicine and pediatrics doctor with Sharp Rees-Stealy Medical Group.
Your risk of a drug interaction can vary based on a number of factors. "Personal traits — genetics, age, weight or gender, for instance — may determine whether an interaction will occur and if it will be harmful," says Dr. Hall. "Specifics about the individual medication, including dosage and when and how you take it, can also play a role."
Regulation of vitamin supplements
The U.S. Food and Drug Administration (FDA) regulates vitamin supplements under a different set of requirements than prescription and over-the-counter medications. Because supplements are not placed under the same rigorous standards for safety and effectiveness, very little information is known about the types of interactions that can occur when mixed with medication. In addition, supplements may vary in potency and content from one brand to another.
Ways to safely take vitamin supplements and medications
Let your doctor know if you plan to take vitamin supplements.
Your doctor can provide you with important advice about the supplements you plan to take based on your current health, medical history and medications. "In particular, if you have any liver or kidney problems you should always consult your physician before starting any supplements," urges Dr. Hall.
Include all vitamins or natural and herbal products when discussing medications with your doctor.
Dr. Hall says this is especially important if you are on multiple prescription medications or blood thinners, or if you have liver or kidney problems. "For example, if you are on a medication that thins the blood, like aspirin or warfarin, your doctor can help to ensure there are no supplement interactions that could raise or lower the concentration of these medications, which could potentially be dangerous."
Read drug labels and follow dosing instructions carefully.
While a conversation with your doctor or pharmacist is the best way to stay informed about the drugs you take, reading the label and patient instructions help you better understand your medications and can help prevent interactions.
Learn more about adverse drug events and how you can better inform and protect yourself when taking multiple medications.