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Chinese Herbs and Your Prescriptions: The Safety Review That Should Happen First

Oct 6
4 min read

The most useful thing I do before writing an herbal formula is ask a boring question: what else are you taking. All of it. The prescription you have been on for eleven years and stopped thinking about. The over-the-counter thing you take twice a week. The supplement your sister recommended. The one you are slightly embarrassed about.

That list is the safety review. Everything else is downstream of it.

The short version

Chinese herbs are pharmacologically active. Several of the most commonly used ones interact with the cytochrome P450 enzyme family — the liver and intestinal enzymes that handle most oxidative drug metabolism and account for nearly half of all drug elimination. An herb that induces or inhibits CYP3A4 can change how much of a prescription drug reaches your bloodstream, in either direction. (Hsieh & Huang, Journal of the Chinese Medical Association, 2026)

That is the mechanism. Now the practical part.

Why "natural" says nothing about safety

Every herb that does anything useful does it by being biochemically active, which is the same property that creates interaction risk. A plant that can move your physiology can also move your drug levels. Those are not two facts, they are one fact viewed from two angles.

The concerning direction is usually not toxicity from the herb itself. It is the herb quietly changing a medication's exposure. Speed up clearance of an antiseizure drug and the dose that has been controlling seizures for six years may stop controlling them. Slow down clearance of an anticoagulant and a stable dose becomes too much. Neither of those failures announces itself as an herb problem. They present as the medication failing.

The herbs I check first

A review of commonly used Traditional Chinese Medicine and Western herbs evaluated effects on the major CYP isoforms — CYP3A4, CYP2C9, CYP2D6, and CYP1A2 — and flagged several with clinically relevant induction or inhibition (Hsieh & Huang, 2026):

  • Danshen (Salvia miltiorrhiza) — a widely used blood-moving herb, and one that warrants particular care alongside anticoagulants

  • Huangqi (Astragalus membranaceus) — one of the most common qi tonics in the materia medica

  • Chaihu (Bupleurum chinense) — the anchor herb in a large family of formulas for constrained qi

  • Ginkgo (Ginkgo biloba)

  • St. John's wort (Hypericum perforatum) — the best-documented offender, a potent CYP3A4 inducer

Two of the first three appear in formulas I might otherwise reach for on a routine Tuesday. That is exactly why the medication list comes before the formula rather than after it.

The interaction picture is more complicated in oncology, where the same herbs can both interfere with and support treatment depending on the agent and the mechanism, and where risk prediction is an active area of research. (Duan et al., Chinese Medicine, 2025) Patients in active cancer treatment get their oncologist looped in before anything is written. Every time.

The five rules I work by

1. The full list, before anything gets written. Prescriptions, over-the-counter drugs, supplements, and anything herbal you are already taking, with doses. Photographs of the bottles are welcome and more accurate than memory.

2. Narrow-therapeutic-index drugs raise the bar, not the caution flag. Warfarin and other anticoagulants, certain antiepileptics, immunosuppressants after transplant, thyroid replacement, some oncology agents, some antiarrhythmics. These are drugs where a modest change in blood level changes the outcome. Some combinations are workable with timing separation and monitoring. Some are not worth attempting, and the right answer is a formula built from different herbs.

3. Sourcing is a safety issue, not a quality preference. Herbs come from suppliers running third-party testing for heavy metals, pesticides, and pharmaceutical adulterants, with documentation available on request. An unsourced formula from an unverified supplier is an unknown quantity in a body you are trying to be careful with.

4. Your other providers get told. The herb and supplement list goes to your prescribing physician. This is not a courtesy — coordination is the actual safety mechanism, and it functions only when both sides have the information. A patient who does not tell their doctor about herbs has removed the person most likely to catch a problem.

5. Reassessment when anything changes. A new prescription, a dose change, a new diagnosis, pregnancy, a surgery on the calendar. Many herbs get stopped before surgery specifically because of bleeding risk and anesthesia interactions. A formula that was appropriate in March may not be appropriate in September.

What to ask any herbalist

If you are seeing someone new, these questions are reasonable and any competent practitioner will welcome them:

  • Did you ask for my complete medication list before writing this formula?

  • Which herbs in this formula have known drug interactions, and what did you check?

  • Where do these herbs come from, and what testing does the supplier do?

  • What should I stop before surgery, and how far ahead?

  • Will you communicate with my other providers?

A practitioner who has not asked for the medication list has skipped the step that matters most. That is worth knowing before you swallow anything.

What this means for you

Chinese herbal medicine is a serious clinical tool with a long track record and real pharmacological weight. Treating it as gentle-because-natural is how people get hurt, and treating it as too dangerous to consider throws away something genuinely useful. The middle position is the correct one: active medicine, prescribed with the same care you would want applied to anything else that changes your biochemistry.

Bring the list. All of it. Including the one you are slightly embarrassed about — I promise I have heard worse, and it might be the one that matters.

Text your medication list to (206) 402-3813 before your first visit and we will have the interaction review done before you sit down.

Courtney M. Zeller, AEMP, L.Ac., MS is the owner and primary practitioner at GoodMedizen in downtown Seattle, where she has practiced acupuncture and Chinese herbal medicine since 2011.

This article is educational and is not medical advice. Do not start or stop any medication based on it. Nothing here is intended to diagnose, treat, cure, or prevent any disease.

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