9 Dangerous Supplement and Medication Interactions to Avoid

When it comes to supplements and medications, mixing certain combinations can pose serious health risks, from reducing drug effectiveness to triggering severe side effects. Understanding which dangerous supplement combinations to avoid ensures that your supplement regimen supports, rather than compromises, your well-being.

1. Vitamin B6 and Levodopa

Taking vitamin B6 with levodopa, a medication used to treat Parkinson’s disease, may reduce its effectiveness. Some forms of levodopa are combined with carbidopa, which helps manage this interaction.

If you’re taking levodopa or levodopa-carbidopa intestinal gel (LCIG), you might develop a vitamin B6 deficiency. This deficiency can lead to anemia, depression, nerve issues, and other health problems. Your healthcare provider might monitor your vitamin levels and recommend B6 supplements if necessary. If you’re on LCIG, it’s important to take B6 only as directed by your provider.

2. Vitamin K and Warfarin

Vitamin K can reduce the effectiveness of blood-thinning medications, such as warfarin.

If you’re taking blood thinners, consult your healthcare provider before using vitamin K supplements or increasing your intake of vitamin K-rich foods. Common sources of vitamin K include romaine lettuce and vegetables like cabbage, broccoli, Brussels sprouts, cauliflower, and kale.

3. Iron or Calcium and Thyroid Medication

Iron and calcium supplements can interfere with how well your body absorbs thyroid hormone replacement medications, such as levothyroxine.

To prevent absorption issues, take these supplements and thyroid medication at least four hours apart.

4. Vitamin C and Aluminum-Based Antacids

Vitamin C can increase the absorption of aluminum found in some antacids, such as Maalox and Gaviscon, which are used to relieve heartburn and indigestion.

To avoid potential toxic levels of aluminum, take vitamin C and antacids at least two hours apart.

5. Blood Thinners and Vitamin E

Vitamin E can raise the risk of bleeding if used with blood-thinning medications, such as warfarin.

If you’re on a blood thinner, consult your healthcare provider before using vitamin E.

6. Various Medications and St. John’s Wort

St. John’s Wort supplements can interact with various medications, such as antidepressants, birth control pills, and blood thinners.

St. John’s Wort can reduce the effectiveness of these medications, and mixing them can cause harmful effects.

7. Goldenseal and Anticoagulants

Goldenseal supplements can interact with medications like anticoagulants, which help prevent blood clotting. This interaction may lower clotting ability, causing bleeding or bruising.

Given the seriousness of the interaction, it’s often recommended to avoid using goldenseal and anticoagulants together.

8. Ginkgo Biloba and Anticoagulants

Ginkgo biloba supplements can also increase the risk of bleeding when taken with anticoagulants like warfarin or aspirin.

9. Licorice Root and Diuretics

Supplements containing licorice root can interact with diuretics and blood pressure medications, making their side effects worse or even causing serious problems, such as potassium imbalances or blood pressure fluctuations.

If you’re taking a prescription medication and thinking about trying a supplement, talk to your provider or pharmacist.

What to Do If You Take These Combinations

If you’re on prescribed meds and using supplements, timing is crucial. Marilyn Tan, MD, advises that thyroid hormone medications should be taken on an empty stomach and spaced four hours apart from supplements, particularly those with calcium and iron.

“Other endocrine medications like the osteoporosis medication Fosamax and the diabetes medication Rybelsus need to be taken on an empty stomach and separated from other medications by at least 30 minutes,” Tan added.

Danielle Crumble Smith, RDN, a registered dietitian nutritionist at Eat Well Live Well, recommends discussing timing your doses with your provider to avoid potential interactions. As a general rule, leave at least two hours between taking supplements and your medications.

When to Ask Your Healthcare Provider 

Your healthcare provider can guide you on what combinations to avoid and how to use supplements with medications safely.

In general, it’s never a bad idea to let your provider know if you’re thinking about trying something new since you may not know about the possible risks involved.

“Supplements seem harmless, but it is important to consult a healthcare professional if you are considering starting a new supplement,” Crumble Smith said. “This is particularly true if you are currently taking medications.”

How to Check for Interactions Yourself

When picking up your medications, you can ask your pharmacist about drug-supplement combinations. Pharmacists are trained to know about drug interactions, including those that can happen with dietary supplements. They also have access to comprehensive databases and tools that let them check for potential interactions.

A pharmacist can advise you on how to use supplements safely, check for interactions, make suggestions about the timing of your doses, or offer alternatives. In some cases, a pharmacist might be able to suggest dose adjustments that could help you avoid an interaction.

Crumble Smith said it’s essential to give a pharmacist a complete list of everything you’re taking, from prescription meds to OTC products and supplements, as this information will help them make the most accurate assessment.

There are also several databases and online tools from reputable resources that you can use to check for potential drug and supplement interactions on your own, including:

Crumble Smith said that while these resources can provide helpful information, they are not a substitute for professional medical advice.

“Always consult with a healthcare provider or pharmacist before starting, stopping, or modifying your medication or supplement regimen,” she said.