Chinese Herbs During Cancer Treatment: Interaction Cautions

First, tell your oncology team

If you are being treated for cancer and use, or are thinking of using, any Chinese herb, tea, patent medicine or supplement, tell your oncologist and your oncology pharmacist before you start and whenever anything changes. NCCIH advises that anyone diagnosed with cancer should consult their health care providers before using any complementary health approach. [1] Do not stop or skip cancer treatment, and do not replace it with herbs. NCCIH states that no complementary approach has been shown to cure cancer or cause it to go into remission. [1]

This page is about interaction and safety cautions. For what research says about Chinese medicine for cancer symptoms, see TCM and cancer: supportive care evidence and safety concerns.

Why herbs matter during cancer treatment

• Some herbs may make treatment less effective. NCCIH says some herbs may make chemotherapy drugs less effective. [1]
• Herbs have side effects of their own, and some interact harmfully with drugs, including cancer drugs. [1]
• Treatment margins are narrow. Memorial Sloan Kettering says a supplement ingredient can increase or lessen the effect of other medicines, and that people being treated for cancer should not take dietary supplements unless a doctor prescribes them or they are part of an approved clinical trial. [2]
• Communication gaps are common. A 2026 review said communication about complementary medicine between patients and physicians remains insufficient and that herb-drug interaction risks are often underestimated in practice. [3]

How interactions can happen (proposed mechanisms)

A review of interactions between herbs and cancer drugs described two kinds. Pharmacokinetic interactions (changing how the body handles a drug) mainly involved induction or inhibition of cytochrome P450 enzymes and the transporter p-glycoprotein. Pharmacodynamic interactions (adding to a drug's effects) were tied to central nervous system effects, liver injury and bleeding. [4] These are mechanisms drawn from lab work and case reports; whether a given herb changes a given patient's outcome is usually unknown.

What the evidence says

The two reviews point in different directions: one documents serious cases and the other finds that formal studies are scarce. One calls for monitoring [4]; the other for a shared database to document herb use with cancer drugs [5]. In plain terms, "no proven interaction" often means "not studied," not "safe."

Examples from the sources

• St. John's wort (a Western herbal product sometimes bought alongside Chinese herbs) can weaken the effects of many medicines, including the cancer drugs irinotecan, imatinib and docetaxel. [7] See St. John's wort interactions.
• Ginger is a common herb; for chemotherapy-related nausea, NCCIH cites a 2019 evaluation of 18 studies that found the evidence mixed. [1]
• Herbs affecting bleeding matter around surgery. See Chinese herbs before and after surgery.
• Hidden ingredients: products with undeclared steroids or other drugs add risks. [8] See undeclared drugs in Chinese patent medicines.
• Liver and kidney strain can complicate cancer treatment; see liver injury from Chinese herbs and aristolochic acid and kidney injury.

Fraudulent "cancer cures"

NCCIH warns that some cancer cures promoted on the internet are dangerous themselves, and others are harmful when people use them instead of seeking effective treatment. [1] Claims such as "treats all forms of cancer" or "more effective than chemotherapy" are red flags. [1]

What to bring to the oncology visit

• The actual bottles, packets or a clear photo of every label (see reading a Chinese patent medicine label).
• Your practitioner's name and contact, if you have one, so the two teams can talk. See questions to ask your TCM practitioner.
• A list of symptoms you hope to ease, so the team can offer evidence-based options.