Herbal Remedies and Cancer Treatment

This information explains herbal remedies and how they can affect your cancer treatment.

One week before you have surgery or start chemotherapy or radiation therapy, you must stop taking any herbal or botanical home remedies or other dietary supplements. This is because they can:

  • Interact with your other medications.
  • Increase or lower your blood pressure.
  • Thin your blood and increase your risk of bleeding.
  • Make radiation therapy less effective.
  • Increase the effects of sedation or anesthesia (medications to make you sleepy).

You can continue to use herbs in your food and drinks, such as using spices in cooking and drinking tea. However, you must stop taking herbal supplements before your treatment. Herbal supplements are stronger than the herbs you would use in cooking.

Common Herbal Supplements and Their Effects

These are some commonly used herbs and their side effects on cancer treatments.


  • Can cause an allergic reaction, such as a rash or difficulty breathing.
  • Can lower the effects of medications used to weaken the immune system.


  • Can lower your blood pressure, fat, and cholesterol levels.
  • Can increase your risk of bleeding.

Gingko (also known as Gingko biloba)

  • Can increase your risk of bleeding.


  • Can lower the effects of sedation or anesthesia.
  • Can increase your risk of bleeding.
  • Can lower your blood glucose (sugar) level.


  • Can make chemotherapy less effective.

St. John’s Wort

  • Can interact with medications given during surgery.
  • Can make your skin more sensitive to radiation or laser treatment.


  • Can increase the effects of anesthesia or sedation.

Herbal formulas

  • Herbal formulas contain different herbs. We don’t know their side effects. You must also stop taking these products 1 week before treatment. Do not start taking herbal formulas again until your doctor tells you it’s safe.

This information does not cover all herbal remedies or possible side effects. Speak with your healthcare provider if you have any questions or concerns.

For more information about herbs and botanicals, visit the Memorial Sloan Kettering (MSK) Integrative Medicine Service website at www.aboutherbs.com.

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