BEWARE: How Herbs Can Cause Problems with Medicines

March 2025

Karen Ensle Ed.D., RDN, FAND, CFCS, FCHS Educator
Rutgers Cooperative Extension of Union County

The National Center for Complementary and Integrative Health (NCCIH) is the Federal Government's lead agency for scientific research on complementary and integrative health approaches. They are one of the 27 Institutes, Centers, and Offices that make up the National Institutes of Health (NIH) within the U.S. Department of Health and Human Services.

The mission of NCCIH is to determine, through rigorous scientific investigation, the fundamental science, usefulness, and safety of complementary and integrative health approaches and their roles in improving health and health care. Their vision is that scientific evidence informs decision making by the public, health care professionals, and health policymakers regarding the integrated use of complementary health approaches in a whole person health framework.

Many people take both herbal supplements and prescriptions or over-the-counter medicines. But, did you know that these medicines and supplements may interact in harmful ways? Some supplements can decrease the effectiveness of medicines, while others can increase their effects, including unwanted side effects. Unfortunately, for many medicines and supplements there's currently little information on possible interactions, and more research is needed. But here are six things you should know about herbs that have a high risk of potential interactions with certain medications.

1. St. John's wort interacts with many types of drugs. In most instances, it speeds up the processes that change the drug into inactive substances, leading to a decrease in drug levels in your body. St. John's wort can also interact with certain types of antidepressants, that increases the risk of serious serotonin-related side effects.
2. Asian ginseng might interact with certain medicines such as calcium channel blockers and other medicines used for high blood pressure such as statin medicines which are used to lower high blood cholesterol. Asian ginseng also affects some antidepressants.
3. Concentrated green tea supplements may reduce blood levels of the cholesterol-lowering drug atorvastatin and the beta-blocker nadolol, a heart medication.
4. The herb goldenseal may change the way your body processes many drugs, including the diabetes medicine metformin.
5. People who take the following medicines including digoxin, cyclosporine, warfarin, and others should take special care to tell their health care providers about their use of herbal supplements. Remember that a drug with a narrow therapeutic index means that if the amount of the drug is even a little too low or too high, it can cause big problems.

When you visit your health care providers, it's important to tell them about all the medicines and supplements you take. Bring a written list of everything you take, how often you take each product, and the doses you ingest. Remember, herbal supplements DO interact with pharmaceutical products in your body and can cause harm if the wrong substances are mixed and consumed.