Traditional Herbs and Prescription Medicines: Interaction Concerns by Medicine Type
How traditional herbs can interact with prescription medicines, which medicine types need extra care, what is known and unknown, and why to tell your pharmacist before combining anything.
Content last updated . This page has not been medically reviewed.
Urgent first
If you have taken a herb and a medicine together and have chest pain, severe bleeding, fainting, seizure or trouble breathing, call 911 in the United States. Poison Help is 1-800-222-1222. Do not stop a prescribed medicine on your own. The NHS advises not stopping any prescribed medicine without first talking to a doctor. [1]What an interaction is
An interaction means that one substance changes how another one works or how your body handles it. A herb can change how well a medicine works. This page lists documented concerns by medicine type. It does not give safe-combination lists, because the research does not support them. Ask a pharmacist or clinician about your own medicines. See also how interactions work.What is and is not known
A systematic review found 128 case reports or case series and 80 clinical trials for just seven popular herbs, and concluded that numerous interactions are documented, though the significance of many is uncertain. [2] Another review of six herbs found the clinical evidence limited and sometimes inconclusive, and that at commonly recommended doses none of those six herbs acted as a potent or moderate inhibitor or inducer of the main drug-processing enzymes. [3] So the picture differs herb by herb: some have strong evidence of interaction, some weak, and for many traditional herbs there are no studies. "No interaction reported" is not the same as "no interaction."Concerns by medicine type
Examples below come from the sources we read. They are illustrations, not complete lists.| Medicine type | Documented concern | Source |
|---|---|---|
| Blood thinners such as warfarin | NCCIH lists warfarin among medicines whose effects St. John's wort can weaken. Reviews also report interactions of ginseng and garlic with warfarin. | [4][2] |
| Antidepressants | St. John's wort can weaken some, and the NHS lists antidepressants as not mixing well with herbal medicines. | [4][1] |
| Birth control | St. John's wort can weaken birth control pills; the NHS lists hormonal contraception. | [4][1] |
| Transplant drugs | NCCIH names cyclosporine, used to prevent rejection of transplanted organs. | [4] |
| HIV medicines | NCCIH names some HIV drugs, including indinavir and nevirapine. | [4] |
| Diabetes, blood pressure, statins | The NHS lists these as medicine types that may not mix well with herbal medicines. | [1] |
St. John's wort is the best-studied example, and NCCIH says it can interact in dangerous, sometimes life-threatening ways with a variety of medicines. [4]
Other risks with medicines
The NHS says not to take herbal medicines if you have kidney or liver problems, or are pregnant or breastfeeding, because not enough is known about their safety. [1] Adulterated products can add a second kind of interaction: a hidden drug you did not know about. [5] See hidden drugs in traditional products.Specific traditions
Interaction concerns for particular systems are in their own pages: Chinese herbal products, Ayurvedic herbs, and Kampo safety.What to do
- Make a written list of everything you take, including the traditional products, and give it to every clinician and your pharmacist. The NHS advises telling any health professional treating you about herbal medicines. [1]
- Ask before starting, stopping or changing a herb.
- Report new symptoms promptly.
Related pages
Interactions by drug class, St. John's wort interactions, and the safety overview.Frequently asked questions
Can I take a traditional herb with my prescription?
Ask your pharmacist or prescriber first; herb and medicine interactions are documented, and many herbs have not been studied. [2]
Which herb has the most documented interactions?
St. John's wort is the best known; NCCIH names many affected medicines. [4]
Does "no interaction found" mean it is safe?
No. Reviews describe the clinical evidence as limited for many herbs. [3]
Should I stop my medicine if I want to use a herb?
No. Do not stop prescribed medicine without talking to a doctor or pharmacist. [1]
Do I need to tell my doctor about teas and powders?
Yes. Tell any health professional treating you about any herbal medicine. [1]
References
- NHS. Herbal medicines. Read 2026-10-22.
- Izzo AA, Ernst E. Interactions between herbal medicines and prescribed drugs: an updated systematic review. Drugs 2009. Read 2026-10-22.
- Hermann R, von Richter O. Clinical evidence of herbal drugs as perpetrators of pharmacokinetic drug interactions. Planta Medica 2012. Read 2026-10-22.
- National Center for Complementary and Integrative Health. St. John's Wort. Read 2026-10-22.
- Coghlan ML and others. Combined DNA, toxicological and heavy metal analyses provides an auditing toolkit to improve pharmacovigilance of traditional Chinese medicine. Scientific Reports 2015. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.