Licorice Root (Gan Cao) in Chinese Medicine
Licorice root (gan cao) in Chinese medicine: its role in herbal formulas, what research found, and why glycyrrhizin can raise blood pressure and lower potassium.
Content last updated . This page has not been medically reviewed.
What it is
Gan cao, one of licorice root's Chinese names, comes from several Glycyrrhiza species, including G. uralensis, G. glabra and G. inflata.[1][2] It is also a familiar flavoring in candy and tea, but NIH notes that many "licorice" products sold in the United States do not contain actual licorice, since anise oil is often used instead.[1] For the tea and food side, see licorice root tea. This page covers the herb as Chinese medicine uses it.
NIH says licorice has a long history in many cultures, including Chinese and Tibetan, for coughing, asthma, wound healing, and diseases of the lungs, liver and arteries.[1] Memorial Sloan Kettering adds that in traditional Chinese medicine licorice is used to enhance or balance the effects of other components in herbal formulas.[2] Because it is a supporting ingredient, check the ingredient list of any multi-herb product for licorice. See Chinese herbal medicine: what it is and what research shows.
What research shows
NIH's summary: some studies in people have been completed, but there is not enough high-quality evidence to clearly support licorice for any health condition.[1]
| Use | What the source found | Strength of evidence |
|---|---|---|
| Recurrent canker sores | A licorice mouth rinse or gargle might reduce ulcer size and pain; in one study an extract plus a medicine worked better than the medicine alone.[1] | Promising but limited |
| Sore throat after a breathing tube during surgery | A licorice gargle or lozenge before surgery might prevent or lessen it.[1] | Promising but limited |
| Eczema and burns (topical gels) | Preliminary evidence; more research needed on effects and safety.[1] | Insufficient evidence |
| Digestive symptoms | It is unclear whether products with licorice alone have an effect; herbal blends are a separate question.[1] | Insufficient evidence |
| COVID-19 | There is no good evidence to support it.[1] | No good evidence of benefit |
Memorial Sloan Kettering's clinician summary describes clinical data on indigestion, reflux and other conditions, and also says that chronic ingestion of even moderate amounts has been associated with high blood pressure and low potassium.[2] Studies of "licorice" may use whole root, extracts, topical products, or products with glycyrrhizin removed, so results do not transfer between them.
Practical guidance
Tell any herbalist, doctor or pharmacist about every licorice-containing tea, candy or formula you use. Do not stop a prescribed medicine because of licorice, and do not use licorice products to treat high blood pressure, heart problems, or ulcers on your own. Persistent symptoms need medical assessment.
Frequently asked questions
What is gan cao?
Gan cao is licorice root, used in traditional Chinese medicine mainly from Glycyrrhiza uralensis and related species.[1][2]
Why does licorice appear in so many Chinese herbal formulas?
Memorial Sloan Kettering says it is used in traditional Chinese medicine to enhance or balance the effects of other components in formulas.[2] That is a traditional role, not a proven effect.
Can licorice raise blood pressure?
Yes. Glycyrrhizin can cause hypertension, fluid retention and low potassium, and chronic intake of even moderate amounts has been linked to these problems.[3][2]
Is deglycyrrhizinated licorice safer?
NIH says oral DGL might be safe for up to 4 months, because the glycyrrhizin has been removed.[1] It is a different product, so ask a pharmacist about your situation.
Can I use licorice in pregnancy?
Large amounts of licorice extract are unsafe in pregnancy and can raise the risk of early delivery.[1] Ask your prenatal clinician before using any licorice product.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Quick safety note
Real licorice root contains glycyrrhizin, which can cause serious problems, including irregular heartbeat and cardiac arrest, especially in large amounts or with long-term use.[1] Even small amounts have been linked to severe effects in people who consume a lot of salt, have high blood pressure, or have heart or kidney conditions.[1] If you have chest pain, a racing or irregular heartbeat, severe muscle weakness or fainting, get emergency care (911 in the US).
Safety, interactions and who should avoid it
How it causes harm: a breakdown product of glycyrrhizin can cause a syndrome that resembles an excess of a salt-retaining hormone (apparent mineralocorticoid excess).[3] The same 2023 review describes poisoning as marked by high blood pressure, fluid retention and low blood potassium, with very large differences between individuals, and says management is mainly stopping licorice and providing symptomatic care.[3]
Memorial Sloan Kettering lists possible side effects including high blood pressure, lethargy, muscle pain, irregular heartbeat, sodium retention, low blood potassium and low platelet count.[2]
- High blood pressure, heart and kidney conditions. Licorice can cause hypertension and may reduce the effectiveness of blood pressure medicine.[2]
- Water pills (diuretics). Licorice may lower blood potassium further.[2]
- Heart medicines (cardiac glycosides). Licorice may increase their effects, which can be harmful.[2]
- Corticosteroids. Interactions between licorice and corticosteroids have been reported.[1]
- Pregnancy. Large amounts of licorice extract (about 250 grams of licorice per week) during pregnancy are unsafe and can increase the risk of delivery before 38 weeks. Little is known about breastfeeding.[1] See pregnancy and breastfeeding.
- Deglycyrrhizinated licorice (DGL). Oral licorice products without glycyrrhizin might be safe for up to 4 months,[1] but they are a different product. A label saying "licorice" does not tell you which kind you have.
Licorice is generally considered safe as a food ingredient,[1] but the glycyrrhizin cautions above apply to people with those conditions. For more on drug interactions, see how interactions work and interactions by drug class. For product quality, see Chinese herbal products: quality, contamination and medicine interactions.
References
- National Center for Complementary and Integrative Health (US NIH), Licorice Root. Read 2026-10-22.
- Memorial Sloan Kettering Cancer Center, Licorice (About Herbs). Read 2026-10-22.
- Adverse effects of licorice consumed as food: An update. Rev Med Interne, 2023, PubMed. Read 2026-10-22.