Common Names

  • Gan cao
  • Sweet root
  • Glycyrrhiza
  • Liquorice

For Patients & Caregivers

How It Works

Licorice may be helpful in treating peptic ulcers, but it has not been shown effective in treating cancer.

In traditional Chinese medicine, licorice is often used in herbal formulas to harmonize the effects of other herbs. Experiments in animals and humans show licorice can mimic the effects of steroid hormones such as aldosterone and estrogen. The substance in licorice that scientists think is responsible for these effects is called glycyrrhizin. However, because glycyrrhizin causes undesirable side effects, it is often removed from licorice products during processing.

Physiologic activity has also been reported for several other compounds in licorice. Isoflavone compounds also mimic estrogens in the human body, and can kill several strains of bacteria and viruses on contact. Other compounds act as blood thinners and inhibit inflammation. In humans, the compound, carbenoxolone, has been used to treat stomach and esophageal ulcers with positive effects. Scientists think that it increases blood flow to and amount of mucus lining the stomach.

Purported Uses

  • To treat bronchitis and chest congestion
    No scientific evidence supports this use.
  • To relieve constipation
    This claim is not backed by research.
  • To treat gastrointestinal disorders such as peptic ulcers
    A substance in licorice called carbenoxolone decreased pain and heartburn and increased healing in patients with peptic ulcers, but major side effects including fluid accumulation, low potassium, and high blood pressure were reported.
  • To treat hepatitis
    Clinical trials in Japan have used a licorice extract containing glycyrrhizin to treat hepatitis B and C, and have shown that glycyrrhizin reduces liver disease. However, there is no proof that deglycyrrhizinated licorice would have the same effect.
  • To reduce inflammation
    Studies in animals support this use, but there is no proof from clinical trials that this effect occurs in humans.
  • To relieve menopausal symptoms
    Studies in animals show that licorice has estrogenic effects, and some of the components of licorice bind estrogen receptors. Human data are lacking.
  • To treat microbial infections
    Studies in animals suggest that licorice has antimicrobial activity, but human data are lacking.
  • To treat prostate cancer
    No scientific evidence supports this use. Licorice is an ingredient in PC-SPES, which has been studied in patients with prostate cancer.

Do Not Take If

  • You take cardiac glycosides: Licorice may increase their effects and cause toxicity.
  • You take insulin: Licorice may have additive effects, possibly causing low blood levels of potassium and high levels of sodium retention.
  • You take warfarin or other blood thinners: Licorice may increase the risk of bleeding.
  • You take MAO-inhibitors (MAOIs): Licorice may have additive effects.
  • You take daunorubicin: Licorice intake can result in increased intracellular concentration of daunorubicin, which may increase its toxic effects.
  • You are taking cytochrome P450 3A and 2D6 substrates: Licorice may increase the risk of side effects of these drugs.
  • You are taking cyclosporine: Licorice greatly reduced the oral bioavailability of cyclosporine by activating P-gp and CYP3A4, which can make it less effective.
  • You are taking cortisol acetate: Licorice increased cortisol availability in tissues, which may increase its side effects.

Side Effects

  • High blood pressure
  • Lethargy
  • Muscle pain
  • Cardiac arrhythmias
  • High sodium retention
  • Low blood levels of potassium
  • Decreased libido in men
  • Suppression of scalp sebum secretion
  • Low blood platelet count

Special Point

Due to the adverse reaction profile of licorice, many studies have been performed using the deglycyrrhizinated licorice (DGL) extract that is free of glycyrrhizin.

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For Healthcare Professionals

Scientific Name

Glycyrrhiza glabra, Glycyrrhiza uralensis

Clinical Summary

Derived from the root of the plant, licorice has been used as a flavoring and sweetening agent. This herb is also an important component of traditional Chinese medicine used to detoxify and enhance or balance the effects of other components in herbal formulas, and as a tonic, expectorant and a demulcent in Ayurveda. A number of compounds including glycyrrhizin are thought to account for its biologic activity.

In vitro and animal data show that licorice has antibacterial (2) (27), antiviral (48), anticancer (3) (4) (28) (29), anti-inflammatory (30), and hepatoprotective (49) properties. Licorice also demonstrated estrogenic effects (7) (8) (10), reduced cardiotoxicity associated with doxorubicin (31), and improved the antitumor effects of cyclophosphamide (32). However, these effects have not been confirmed in humans.

Licorice demonstrated effectiveness in reducing dyspepsia (1) and hyperlipidemia (33) in clinical studies.

Purported Uses

  • Bronchitis
  • Chest congestion
  • Constipation
  • GI disorders
  • Hepatitis
  • Inflammation
  • Menopausal symptoms
  • Microbial infection
  • Peptic ulcers
  • Primary adrenocortical insufficiency
  • Prostate cancer

Mechanism of Action

Glycyrrhizin has been reported to bind to glucocorticoid and mineralocorticoid receptors and exerts its effect via inhibition of 11b-hydroxysteroid dehydrogenase (12). Licorice can reduce serum testosterone by inhibiting 17-hydroxysteriod dehydrogenase (35) (36). Licorice contains isoflavones and other constituents that have estrogen receptor-modulating activities (8) (10). The flavone and liquiritigenin components selectively activate ER-alpha (11).

Licorice demonstrated chemopreventive effects by modulating expression of Bcl-2/Bax proteins, which act as apoptotic regulatory factors (3), and via inhibiting carcinogenesis (4). In another study, licorice inhibited P-glycoprotein (P-gp), resulting in increased intracellular concentration of the chemotherapy agent daunorubicin, which is a substrate of P-gp (34).

The most common side effect of licorice is hypokalemic hypertension, which occurs secondary to inhibition of 11beta-hydroxysteroid dehydrogenase, a renal enzyme responsible for converting cortisol to cortisone. This inhibition results in enhancing the mineralocorticoid effects of cortisol (36) that include sodium retention and excretion of potassium.


Due to the adverse reaction profile of licorice, many studies have been performed using the deglycyrrhizinated licorice (DGL) extract that is free of glycyrrhizin.

Adverse Reactions

Hypertension (16) (45), lethargy, muscle pain, sodium retention, hypokalemia (17) (18) (19) (20) (26) (40) (41), adrenal crisis (21), ventricular fibrillation (22), cardiac arrythmias (23), carpal tunnel syndrome (24), glycyrrhizic acid poisoning (25), leukoderma (42), and thrombocytopenia (43)

Herb-Drug Interactions

Cardiac glycosides: Licorice may potentiate toxicity (24).
Insulin: Licorice may have a synergistic effect possibly causing hypokalemia and sodium retention with concomitant use (38) .
Anticoagulants: Licorice may increase the metabolism and clearance of warfarin (19).
MAO-inhibitors (MAOIs): Licorice may potentiate activity of MAOIs (37) (8)
P-Glycoprotein (P-gp) substrates: Licorice inhibited P-gp, resulting in increased intracellular concentration of the chemotherapy agent daunorubicin, which is a substrate of P-gp (34).
Cytochrome P450 substrates: Glycyrrhizin, a major ingredient of licorice, induces CYP3A (39) and CYP2D6 (44), and can affect the intracellular concentration of drugs metabolized by this enzyme.
Cyclosporine: Licorice greatly reduced the oral bioavailability of cyclosporine by activating P-gp and CYP3A4 (46).
Cortisol acetate: Licorice increased cortisol availability in tissues in the hours following oral cortisone acetate administration (47).

Dosage (OneMSK Only)


  1. Gupta VK, Fatima A, Faridi U, et al. Antimicrobial potential of Glycyrrhiza glabra roots. J Ethnopharmacol. Mar 5 2008;116(2):377-380.

  2. De Smet PAGM. Adverse Effects of Herbal Drugs. Vol 3. New York: Springer: 1997.

  3. Lin SH, Yang SS, Chau T, et al. An unusual cause of hypokalemic paralysis: chronic licorice ingestion. Am J Med Sci. Mar 2003;325(3):153-156.

  4. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy (OR): Eclectic Medical Publications; 1998.

  5. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide for Health-Care Professionals. 1st ed. London: Pharmaceutical Press; 1996.

  6. Blumenthal M, Goldberg A, Brinckmann J, et al. Herbal Medicine, Expanded Commission E Monographs. Austin: American Botanical Council; 2000.

  7. Somjen D, Knoll E, Vaya J, et al. Estrogen-like activity of licorice root constituents: glabridin and glabrene, in vascular tissues in vitro and in vivo. J Steroid Biochem Mol Biol. Jul 2004;91(3):147-155.

  8. Mersereau JE, Levy N, Staub RE, et al. Liquiritigenin is a plant-derived highly selective estrogen receptor beta agonist. Mol Cell Endocrinol. Feb 13 2008;283(1-2):49-57.

  9. Tyler V. Herbs of Choice, the Therapeutical Use of Phytomedicinals. Binghamton: Pharmaceutical Press; 1994.

  10. Stormer FC, Reistad R, Alexander J. Glycyrrhizic acid in liquorice—evaluation of health hazard. Food Chem Toxicol. Apr 1993;31(4):303-312.

  11. Ichikawa T, Ishida S, Sakiya Y, et al. Biliary excretion and enterohepatic cycling of glycyrrhizin in rats. J Pharm Sci. Jul 1986;75(7):672-675.

  12. Breidthardt T, Namdar M, Hess B. A hypertensive urgency induced by the continuous intake of a herbal remedy containing liquorice. J Hum Hypertens. 2006 Jun;20(6):465-6.

  13. Mumoli N, Cei M. Licorice-induced hypokalemia. Int J Cardiol. 2008 Mar 14;124(3):e42-4.

  14. Templin C, Westhoff-Bleck M, Ghadri JR. Hypokalemic paralysis with rhabdomyolysis and arterial hypertension caused by liquorice ingestion. Clin Res Cardiol. 2009 Feb;98(2):130-2.

  15. Isaia GC, Pellissetto C, Ravazzoli M, Tamone C. Acute adrenal crisis and hypercalcemia in a patient assuming high liquorice doses. Minerva Med. 2008 Feb;99(1):91-4.

  16. Gerritsen KG, Meulenbelt J, Spiering W, et al. An unusual cause of ventricular fibrillation. Lancet. 2009 Mar 28;373(9669):1144.

  17. Tacconi P, Paribello A, Cannas A, Marrosu MG. Carpal tunnel syndrome triggered by excessive licorice consumption. J Peripher Nerv Syst. 2009 Mar;14(1):64-5.

  18. Yorgun H, Aksoy H, Sendur MA, et al. Brugada syndrome with aborted sudden cardiac death related to liquorice-induced hypokalemia. Med Princ Pract. 2010;19(6):485-9.

  19. Caubet-Kamar N, Tubery M, Garrouste C, Lauque D, Kamar N. Harmful effect of saline infusion in a patient with glycyrrhizic acid poisoning. CJEM. 2010 May;12(3):224-5.

  20. Kim YH, Shin EK, Kim DH, et al. Antiangiogenic effect of licochalcone A. Biochem Pharmacol. 2010 Oct 15;80(8):1152-9.

  21. Chandrasekaran CV, Deepak HB, Thiyagarajan P, et al. Dual inhibitory effect of Glycyrrhiza glabra (GutGard™) on COX and LOX products. Phytomedicine. 2010 Sep 21.

  22. Gol’dberg ED, Amosova EN, Zueva EP, et al. Licorice preparations improve efficiency of chemotherapy and surgical treatment of transplanted tumors. Bull Exp Biol Med. 2008 Feb;145(2):252-5.

  23. Hasani-Ranjbar S, Nayebi N, Moradi L, et al. The efficacy and safety of herbal medicines used in the treatment of hyperlipidemia; a systematic review. Curr Pharm Des. 2010;16(26):2935-47.

  24. Nabekura T, Yamaki T, Ueno K, Kitagawa S. Inhibition of P-glycoprotein and multidrug resistance protein 1 by dietary phytochemicals. Cancer Chemother Pharmacol. 2008 Oct;62(5):867-73.

  25. Armanini D, Mattarello MJ, Fiore C, et al. Licorice reduces serum testosterone in healthy women. Steroids. 2004 Oct-Nov;69(11-12):763-6.

  26. Armanini D, Bonanni G, Mattarello MJ, et al. Licorice consumption and serum testosterone in healthy man. Exp Clin Endocrinol Diabetes. 2003 Sep;111(6):341-3.

  27. Tu JH, He YJ, Chen Y, et al. Effect of glycyrrhizin on the activity of CYP3A enzyme in humans. Eur J Clin Pharmacol. 2010 Aug;66(8):805-810.

  28. Yorgun H, Aksoy H, Sendur MA, et al. Brugada syndrome with aborted sudden cardiac death related to liquorice-induced hypokalemia. Med Princ Pract. 2010;19(6):485-9.

  29. Pant P, Nadimpalli L, Singh M, Cheng JC. A case of severe hypokalemic paralysis and hypertension. Licorice-induced hypokalemic paralysis. Am J Kidney Dis. 2010 Jun;55(6):A35-7.

  30. Celik M, Karakus A, Zeren C, et al. Licorice induced hypokalemia, edema, and thrombocytopenia. Hum Exp Toxicol. 2012 Dec;31(12):1295-8.

  31. Pandit S, Ponnusankar S, Bandyopadhyay A, Ota S, Mukherjee PK. Exploring the possible metabolism mediated interaction of Glycyrrhiza glabra extract with CYP3A4 and CYP2D6.Phytother Res. 2011 Oct;25(10):1429-34.

  32. Ruiz-Granados ES, Shouls G, Sainsbury C, Antonios T. A salty cause of severe hypertension. BMJ Case Rep. 2012 Feb 25;2012. doi:pii: bcr1220115336. 10.1136/bcr.12.2011.5336.

  33. Hou YC, Lin SP, Chao PD. Liquorice reduced cyclosporine bioavailability by activating P-glycoprotein and CYP 3A. Food Chem. 2012 Dec 15;135(4):2307-12.

  34. Methlie P, Husebye EE, Hustad S, Lien EA, Løvås K. Grapefruit juice and licorice increase cortisol availability in patients with Addison’s disease.Eur J Endocrinol. 2011 Nov;165(5):761-9.

  35. Kuo KK, Chang JS, Wang KC, Chiang LC. Water extract of Glycyrrhiza uralensis inhibited enterovirus 71 in a human foreskin fibroblast cell line. Am J Chin Med. 2009;37(2):383-94.

  36. Huo HZ, Wang B, Liang YK, Bao YY, Gu Y. Hepatoprotective and Antioxidant Effects of Licorice Extract against CCl(4)-Induced Oxidative Damage in Rats. Int J Mol Sci. 2011;12(10):6529-43.

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