How Supplements Can Interact with Medications
Lindsay Knake
| 4 min read
Lindsay Knake is a brand journalist for Blue Cross B...
Key Takeaways
- Supplements can alter how prescription and over‑the‑counter drugs work, sometimes speeding up or slowing down drug metabolism and leading to reduced efficacy or increased side effects.
- Common herbs and minerals—including ashwagandha, glucosamine, magnesium and St. John’s Wort—have documented interactions with medications such as anti‑anxiety drugs, blood thinners, antibiotics and birth‑control pills; vitamin E may also raise bleeding risk when taken with anticoagulants.
- Because supplements are not FDA‑approved, consumers should verify third‑party certification, rely on food sources for most nutrients and always discuss any new supplement with a primary care provider to avoid dangerous drug‑supplement interactions.
There’s a lot of marketing around supplements and their benefits.
But supplements aren’t always free of risks, and sometimes they can interact with medications in negative or dangerous ways. If you take a supplement or are considering taking one, here are some things to know about how to safely approach using medications and supplements.
How supplements can interact with medications
Supplements, which may be vitamins, minerals or herbs, can affect the way your body processes prescription and over-the-counter drugs, according to the National Institutes of Health (NIH). Some supplements break down medications faster than expected, which means there is less medication in your bloodstream. Other medications can slow the breakdown, leaving medication in your body for longer than normal.
Both processes can cause harm, including leaving your body without the medication it needs or causing side effects from too much. Here are a few examples of supplements that can interfere with drugs:
Ashwagandha
Ashwagandha, an herb marketed to aid with better sleep and lower stress, may have sedative effects and may increase the effects of anti-anxiety drugs such as Xanax and Valium, according to the NIH. This herb may also interact with diabetes and blood pressure medications.
Glucosamine
Glucosamine is a supplement for joint health. It is associated with an increased risk of bleeding in people taking blood thinners such as warfarin, according to the NIH.
Magnesium
This mineral is essential for overall health, including muscle function and blood pressure. It’s also touted as a health hack for better sleep and reduced anxiety, although research is limited. Magnesium may interfere with antibiotics and drugs to treat osteoporosis if you take high doses of it as a supplement or don’t space out timing for when you take medication, per the NIH.
St. John’s Wort
St. John’s Wort is an herb that may help improve symptoms of mild depression and menopause. It also may prevent the effectiveness of several medications, per the NIH, including:
- Oral birth control
- Allergy medication such as fexofenadine
- Antidepressants
- Blood thinners
- Some cancer treatments
- Some heart medications
Vitamin E
A vitamin E supplement may also increase risk of bleeding for people taking a blood thinner, according to the American Heart Association.
These are just a few examples of supplements that can interact with your medications. To search for a supplement you may be considering, the National Library of Medicine maintains a database of drug and supplement side effects and a database of information about common supplements.
Beware of marketing claims on supplements
Supplements are a $12 billion-a-year industry, and many make all kinds of health promises. But supplements are not regulated by the U.S. Food and Drug Administration (FDA) and do not require approval before marketing. Claims on supplements, such as “natural” or “herbal” are marketing terms and don’t mean the product is safe, per the FDA.
While taking a multivitamin may be safe for most people, it’s important to note that multivitamins are not associated with reducing the risk of conditions such as heart disease, heart attacks, cancer and cognitive decline, according to Johns Hopkins University.
For most people, it’s best to get vitamins, minerals and nutrients from food. Eat a diet full of fruits and vegetables, whole grains, healthy fats and lean proteins. Some supplements, such as folic acid for pregnant women or iron for people with iron deficiency, can help with specific risks and conditions.
If you need to take a supplement, look for products approved by the United States Pharmacopeia (USP) or National Science Foundation (NSF). This means they are tested and certified by an independent third party that the product contains what the label says and meets quality standards.
Talk to your primary care provider (PCP) before taking any dietary supplements. If you start a new medication or want to take a supplement, discuss possible interactions with your PCP.
Photo credit: Getty Images
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