What to know about vitamins and supplements if you’re taking prescription medication

A woman reviews the labels of her supplements and vitamins to check if they could interact with her prescription medication.

Certain dietary supplements can pose a real danger to your health if you’re taking them along with some commonly prescribed medications.

More than half of U.S. adults take at least one dietary supplement, whether it be vitamins, minerals, herbs, botanicals, amino acids, or enzymes like probiotics.1 While dietary supplements are often marketed as “all natural” or “herbal,” they can pose risks if you take one or more prescription medications.

Here’s what you need to know about mixing dietary supplements with medication, as well as some of the most common supplements that cause medication interactions.

What is a medication interaction?

A medication interaction happens when you take a vitamin, supplement, food, drink, or another medication that alters the clinical effects of a medication you’re taking. This means it changes how the medication is absorbed, broken down, and eliminated from the body. In some cases, your medication could be less effective. In other cases, it could lead to medication overdose.

Medication interactions can also make side effects of a medication worse or cause unexpected and potentially dangerous side effects. The more medications and supplements you take, the higher your risk of an interaction.

Popular dietary supplements and the medications they interact with

The FDA does not review dietary supplements for effectiveness like it does with over-the-counter and prescription medications, and it doesn’t require that supplement companies list interaction warnings on their labels. It’s up to the manufacturers and distributors to ensure their products are safe.

Below are some of the most popular dietary supplements that can interact with commonly prescribed medications. Keep in mind that this list is not comprehensive.

  • St. John’s wort, which is commonly used to treat moderate depression or reduce menopause symptoms, speeds up the absorption of medications in the body, making them less effective. St. John’s wort can be particularly dangerous and even life-threatening when taken in conjunction with HIV/AIDS medications, heart disease medications, depression medications, birth control pills, anti-rejection medications given after transplant surgery, and even the COVID-19 antiviral Paxlovid.
  • Ginkgo biloba, which is commonly used to treat memory disorders and improve blood circulation, contains several compounds that thin the blood and block an enzyme that causes blood clotting. This is particularly dangerous if you take an anticoagulant like warfarin because it can lead to internal bleeding or stroke.
  • CoQ10, which is often touted for its potential cardiovascular benefits, interferes with blood thinners and makes them less effective, potentially causing blood clots. Vitamin C also has this same effect.
  • Probiotics, vitamin A, and iron supplements can all reduce the effectiveness of antibiotics.
  • Milk thistle and other herbs that decrease blood sugar may interact with diabetes medications like metformin, causing hypoglycemia.
  • Red yeast rice, which is used to lower cholesterol, improve digestion, and improve circulation, can enhance the effects of statins and raise a person’s risk for liver or kidney problems.

Make sure you read the full list of ingredients on your dietary supplements, and always talk to your doctor or pharmacist before starting any new dietary supplements to help decrease the chance of a dangerous medication interaction.

Understand your risk

There are certain groups of people who are at higher risk for medication interactions associated with dietary supplements.

  1. Children. Kids metabolize different substances at different rates depending on how old they are, which increases the risk of adverse reactions when taking dietary supplements with other medications. It’s important to discuss all dietary supplements with your child’s pediatrician to avoid potential complications.
  2. Seniors. Older adults are more likely to take multiple medications, and therefore, it’s more likely that one or more of those medications will interact with other dietary supplements.
  3. Surgical patients. Dietary supplements can decrease the effectiveness of critically important anti-rejection medications, as well as medications prescribed before, during, and after surgery. They can also cause changes in heart rate, blood pressure, response to anesthesia, and bleeding risk.
  4. Pregnant and breastfeeding women. Most dietary supplements haven’t been tested on women who are pregnant or breastfeeding. Talk to your doctor or pharmacist before taking any dietary supplements.
  5. Those taking medication with a narrow therapeutic range. This means that even a slight variation in the absorption of your medication can lead to serious complications. Some examples include seizure medications, thyroid medications, and blood thinners. If you take these medications, reach out to your pharmacist to discuss the potential risks.

Talk to a healthcare professional

The best way to prevent medication interactions is to be proactive. Keep a list of all of your medications, including their dosages and how often you take them, and have that list available to share with your doctor or pharmacist before starting any dietary supplements.

If your health benefits include Express Scripts® Pharmacy, our pharmacists are available 24/7 to answer all of your medication questions from the privacy of your own home. They can help you determine if you need to stop any supplements for a period of time or suggest alternative medications that don’t pose a risk.

1 Centers for Disease Control and Prevention: Dietary Supplement Use Among Adults: United States, 2017-2018 (February 2021): https://www.cdc.gov/nchs/products/databriefs/db399.htm.

Posted date: May 25, 2023

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