Supplement Interactions: Why You Need to Talk to Your Doctor

How Dietary Supplements Can Interact with Medications

Dietary supplements—including vitamins, minerals, herbs, and other botanicals—can interact with prescription and over-the-counter medications. These interactions may make a drug less effective, increase the risk of side effects, or lead to unexpected health problems. The U.S. Food and Drug Administration (FDA) does not review dietary supplements for safety or effectiveness before they are marketed, so it’s up to you and your healthcare team to manage potential risks.

Many adults in the United States use supplements alongside prescription drugs. Estimates suggest that between 34% and 66% of U.S. adults take both. Despite this, many people do not tell their healthcare providers about every supplement they use. That gap in communication can increase the chance of an unrecognized interaction.

Sources: U.S. National Library of Medicine (PubMed Central)

Common Supplement Categories and Known Interaction Risks

Some well-known supplements have documented interactions with medications. The following are examples based on the research literature:

Garlic: Often used for cardiovascular health, garlic may interact with blood thinners and other medications, potentially increasing bleeding risk.

Ginkgo biloba: Commonly used for memory or circulation, ginkgo may also interact with anticoagulant or antiplatelet drugs, raising bleeding concerns.

Ginseng: Used for energy or general health, ginseng may affect blood sugar and blood pressure, and may interact with diabetes or blood pressure medications.

Licorice root: Found in some herbal products, licorice can increase blood pressure and may interact with diuretics or heart medications.

These examples show that even common, 'natural' products are not risk-free. The exact risk depends on the dose, the medication, and your health status.

Special caution is needed for people with cardiovascular disease. Herbal products can interact with heart medications and may cause adverse effects. Patients in this group should always discuss supplement use with their cardiologist or pharmacist.

• Always read labels and look for potential warnings, but be aware that many products lack specific warnings about interactions.

Sources: U.S. National Library of Medicine (PubMed Central)

Supplements That May Interact with Prescription Drugs

Beyond the herbs listed above, certain supplements marketed for skin, hair, and nail health may also contain ingredients that pose interaction risks. For example, saw palmetto, an extract sometimes used for hair loss, inhibits an enzyme called 5-alpha-reductase. That same enzyme is a target for medications used to treat an enlarged prostate, so taking saw palmetto alongside such drugs could change the drug's effect.

A 2020 study of retail skin, hair, and nail supplements found that many products did not carry warnings about potential drug interactions, despite containing active botanicals. This highlights why it's risky to assume that a retail supplement is safe just because it's sold over the counter.

Supplement labels are not reviewed by the FDA for accuracy before products reach store shelves. That means the presence, dose, and purity of ingredients are not guaranteed, further complicating any potential interaction.

Sources: U.S. National Library of Medicine (PubMed Central)

How to Review Your Supplement and Medication List with a Clinician

Before you start a new supplement—or if you're already taking one—make a list of everything you take, including prescription drugs, over-the-counter medicines, and supplements. Write down the name of each product, the dose, and how often you take it. Bring this list to every appointment with your doctor or other healthcare professional.

Healthcare professionals themselves have identified incomplete supplement documentation in electronic medical records as a patient safety concern. In a 2023 qualitative study, clinicians noted that incomplete records make it harder to catch potential interactions. By giving your provider a complete list, you improve the safety of your care.

You should tell your doctor about all supplements you take, even if you think they are harmless. This is especially important if you have a chronic condition, take multiple medications, or are preparing for surgery. Your provider can tell you if any supplements need to be stopped or adjusted.

• Include supplements you take occasionally, such as herbal teas or protein powders.
• Include vitamins and minerals, even if they seem routine.
• Update the list whenever you start or stop something.
• Do not stop a prescribed medication on your own to make room for a supplement; always consult your doctor first.

Sources: U.S. National Library of Medicine (PubMed Central)

Role of the Pharmacist in Checking Interactions

Pharmacists are medication experts who can review your supplement and medication list for potential interactions. When you fill a prescription, ask the pharmacist to check your list. They can help you understand whether a supplement might affect how a drug works or increase side effects.

It's a good idea to use one pharmacy for all your prescriptions and to bring your supplement list with you each time. If you use more than one pharmacy, make sure each pharmacist knows about all your medications and supplements.

Red Flags and When to Seek Immediate Help

Red flags: Watch for unusual bleeding or bruising, fast or irregular heartbeat, severe dizziness or fainting, swelling of the face or tongue, difficulty breathing, seizures or loss of consciousness. These may signal a dangerous interaction.

Because interactions can also happen without obvious symptoms—for instance, a supplement might make a heart drug less effective—do not wait for a symptom to appear. Get a professional review of your medication and supplement list before you combine them.

For emergency symptoms such as chest pain, severe bleeding, or difficulty breathing, call 911 or go to an emergency room right away.