Gan Cao
StarGlycyrrhiza uralensis Fisch.
Synonyms: Glycyrrhiza uralensis Fisch. ex DC., Liquiritia uralensis (Fisch.) Moench
Also known as: Kanzō甘草 カンゾウ · Kampo; Gamcho甘草 감초 · Korean; Cam thảo · Vietnamese; Kan Ts'ao · Wade–Giles
Safety at a glance
- High risk · Do not combine with Hai Zao, Gan Sui, Jing Da Ji or Yuan Hua (十八反)
- High risk · With digoxin, digitalis: licorice-induced hypokalaemia potentiates digoxin toxicity
- Caution · Breastfeeding: caution — glycyrrhizin exposure to infant; limit dose/duration
- Caution · With antihypertensive, lisinopril, amlodipine: pseudoaldosteronism raises BP / causes hypokalaemia
- Caution · 5 recorded drug interactions, 2 major or contraindicated
- Note · Not beyond 28 days at a time
- Note · Contraindications or side effects are listed
No rule in our tables for this herb: pregnancy, dose ceiling. This is not a safety clearance.
Not graded — No toxicity grade is recorded. Most herbs in the catalogue carry none.
Traditionally used for
- Nose & throat
- Cough & breathing
- Energy & fatigue
Cautions & contraindications
- Heart conditions
☯ TCM Properties
Tonifies the Spleen and augments Qi; Moistens the Lungs, resolves Phlegm and stops coughing; Moderates spasms and alleviates pain; Clears Heat and relieves Fire toxicity; Moderates and harmonizes the harsh properties of other herbs
Traditional Chinese Uses
Gan Cao (licorice root) is the most widely used herb in all of Chinese medicine — its mild, sweet flavor and neutral character make it an ideal harmonizer that both strengthens Spleen and Lung Qi and mediates the interactions between other herbs in a formula. It stops cough, clears Heat toxin for sore throats and abscesses, relieves spasmodic pain in the extremities and abdomen, and modifies the harsh or toxic properties of other herbs. Honey-frying enhances its tonic action. It is the standard formula-harmonizing herb in TCM.
Western Herbalism Properties
Pharmacological Effects
- Glucocorticoid-like: Glycyrrhizin (600 μg/kg i.p.) caused thymic atrophy and adrenal enlargement in rats; in Addison's patients and healthy subjects i.m. glycyrrhizin prolonged cortisone action; glycyrrhetic acid inhibited 5β-reduction of cortisol and aldosterone in vitro.
- Mineralocorticoid-like: Extract, glycyrrhizin and glycyrrhetic acid reduced urine volume and sodium excretion and increased potassium excretion; clinical use may cause pseudo-aldosteronism with edema and hypertension, via glycyrrhetic acid binding kidney mineralocorticoid receptors.
- Antiinflammatory: Glycyrrhizin and glycyrrhetic acid inhibited granulation, paw edema and granuloma in rats; glycyrrhetic acid ~1/10 as potent as cortisone.
- Immunosuppressive / antiallergic: LX (2 mg/rat i.v.) inhibited macrophage immune reaction, prolonged graft survival and suppressed antibody production; glycyrrhizin inhibited passive cutaneous anaphylaxis and agonist-induced smooth muscle contraction.
- Antiulcer / spasmolytic: Extract (250 mg/kg) inhibited pylorus-ligation ulcers in rats; FM 100 (100 mg/kg i.p.) completely inhibited ulcer formation and reduced gastric secretion by direct mucosal action; FM 100 and isoliquiritigenin were spasmolytic on guinea pig intestine.
- Antitussive / expectorant: Glycyrrhetic acid derivative (1 mg/kg s.c.) inhibited 80% of ammonia-induced cough in guinea pigs, comparable to codeine, via central action; glycyrrhizin assists expectoration.
- Hepatoprotective: Extract, glycyrrhizin and glycyrrhetic acid protected rats against CCl4 injury and experimental cirrhosis; 18β/18α-glycyrrhetic acid more potent than glycyrrhizin.
- Antiviral: Glycyrrhizin (8 mM) inhibited vaccinia, HSV-1, Newcastle disease and VSV in HEP-2 cells; active against VZV; completely inhibited HIV plaque formation in MT-4 cells at 0.5 mg/ml (ID50 0.125 mg/ml).
- Other: Antitumor (glycyrrhizin, glycyrrhetic acid, liquiritin), antipyretic, analgesic (FM 100) and antidiuretic activities reported.
Source: Zhu YP. Chinese Materia Medica: Chemistry, Pharmacology and Applications. Harwood Academic, 1998, p. 567.
Used In Formulas (515)
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Gallery
Botanical Description
Glycyrrhiza uralensis is a perennial herb in the pea family (Fabaceae), growing from a stout, woody, deep-reaching taproot and spreading rhizomes. Erect, branched or unbranched stems reach 30–70 cm, occasionally to 120 cm, and are glandular and finely downy. The leaves are alternate and pinnately compound with 7–17 oval to lance-shaped leaflets. Small pale purple to violet pea-like flowers are borne in dense axillary spikes in mid to late summer, followed by oblong, curved, glandular-hairy pods. The medicinal part is the dried root and rhizome — cylindrical, 10–30 cm long and 1–2 cm thick, brownish-grey and longitudinally wrinkled outside, pale yellow and fibrous within — which is rich in glycyrrhizin and provides the herb Gan Cao.
Dry, sunny grasslands, sandy plains, and hillsides across the temperate steppe of northern China, Mongolia, and Central Asia.
Glycyrrhiza uralensis is widely distributed across the temperate steppe of northern China, Mongolia and Central Asia. Heavy wild harvesting for medicine has led to local depletion and desertification concerns in parts of its range, and it is increasingly cultivated to reduce pressure on wild stands.
Active Constituents
Glycyrrhizin (glycyrrhizic acid)
Triterpenoid saponinConcentration: ~2–9% of dried root
The principal sweet-tasting saponin (roughly 50× sweeter than sucrose) and the pharmacopoeial marker compound. Anti-inflammatory, antiviral and hepatoprotective. Hydrolysed in the gut to 18β-glycyrrhetinic acid, its active metabolite.
18β-Glycyrrhetinic acid
Triterpenoid aglyconeConcentration: Metabolite of glycyrrhizin
Active metabolite responsible for much of licorice's activity. Inhibits 11β-hydroxysteroid dehydrogenase type 2, slowing cortisol breakdown — the mechanism behind licorice's corticosteroid-like effects and, in excess, pseudoaldosteronism.
Liquiritin / liquiritigenin
Flavanone glycoside / aglyconeConcentration: Major flavonoids
Flavonoids credited with antitussive, expectorant, antispasmodic and antioxidant actions. Liquiritin is a pharmacopoeial quality marker alongside glycyrrhizin.
Isoliquiritigenin
ChalconeConcentration: Minor
Antioxidant and antispasmodic chalcone; studied for oestrogenic and anti-tumour activity in vitro.
Licochalcone A
ChalconeConcentration: Characteristic of G. inflata
Antimicrobial and anti-inflammatory chalcone; a chemotaxonomic marker distinguishing G. inflata from other licorice species.
Glabridin
IsoflavanConcentration: Characteristic of G. glabra
Antioxidant isoflavan and tyrosinase inhibitor (skin-lightening interest). Found mainly in G. glabra rather than G. uralensis.
⚠ Drug Interactions
Digoxin / cardiac glycosides
Glycyrrhizin-induced potassium loss (pseudoaldosteronism) sensitises the myocardium to cardiac glycosides.
Clinical note: Hypokalaemia can precipitate serious, potentially fatal arrhythmias. Avoid concurrent use, or monitor serum potassium and digoxin closely.
Loop & thiazide diuretics
Additive potassium depletion — both licorice and these diuretics lower serum potassium.
Clinical note: Risk of significant hypokalaemia (muscle weakness, cramps, arrhythmia). Avoid or monitor electrolytes.
Corticosteroids
Glycyrrhetinic acid inhibits 11β-HSD2, slowing cortisol inactivation and potentiating corticosteroid effects.
Clinical note: May intensify sodium/water retention, hypertension and hypokalaemia. Use cautiously with systemic steroids.
Antihypertensives
Licorice raises blood pressure through pseudoaldosteronism, opposing antihypertensive therapy.
Clinical note: Can reduce the efficacy of blood-pressure medication and worsen control. Avoid in uncontrolled hypertension.
Warfarin
Some evidence that licorice increases warfarin clearance, potentially lowering INR.
Clinical note: Limited data. Monitor INR if licorice is started or stopped.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| Decoction (raw Gan Cao) | 2–10 g | Daily, in divided doses | — | Adult |
Chinese Pharmacopoeia 2020, Vol. I 【甘草】【用法与用量】2～10g. Bensky, Clavey & Stöger, Chinese Herbal Medicine: Materia Medica, 3rd ed. (2004): 1.5–9 g. |
| Decoction (high dose, short-term) | 15–30 g | Daily | Short courses only | Adult |
Bensky, Clavey & Stöger, Chinese Herbal Medicine: Materia Medica, 3rd ed. (2004): when a large dosage is required, 15–30 g can be used. Larger doses are used for clearing Fire toxicity (e.g. sore throat, drug/food toxicity) or acute spasmodic pain. Prolonged high-dose use risks pseudoaldosteronism (hypertension, hypokalaemia, oedema) and should be monitored. |
| Honey-fried (Zhi Gan Cao) | 2–10 g | Daily | — | Adult |
Chinese Pharmacopoeia 2020, Vol. I 【炙甘草】【用法与用量】同甘草 (2～10g). Bensky, Clavey & Stöger, Chinese Herbal Medicine: Materia Medica, 3rd ed. (2004) gives 1.5–9 g for Gan Cao. The honey-fried form is warmer and more tonifying; it is the form used to tonify Spleen and Heart Qi and to restore the pulse, e.g. Zhi Gan Cao Tang (Honey-fried Licorice Decoction) and Li Zhong Wan (Regulate the Middle Pill). |
Dosage Calculator
⚖ Dosage Calculator
A weight-based mathematical estimate for Gan Cao. Not a prescription.
Preparation Methods
Raw Gan Cao decoction
Parts: root, rhizome
Dried, unprocessed root and rhizome sliced and decocted with the other formula ingredients. Favoured for clearing Heat, resolving toxicity and moistening the Lung.
Honey-fried (Zhi Gan Cao)
Parts: root, rhizome
Sliced root stir-fried with honey until golden and no longer sticky. Processing warms the herb and enhances its Qi- and Blood-tonifying, pulse-restoring action.
Powder / granule
Parts: root, rhizome
Milled to powder or prepared as a concentrated granule for direct dosing where decoction is impractical.
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Sour and sweet combine to generate yin and relax spasm, relieving cramping pain of the limbs and abdomen.
Core pair of a classical formula — Shao Yao Gan Cao Tang, Shang Han Lun (Zhang Zhongjing)
Spleen and lung yang are warmed while the middle is tonified, treating cold in the lung and middle burner.
Core pair of a classical formula — Gan Cao Gan Jiang Tang, Shang Han Lun (Zhang Zhongjing)
Acrid and sweet combine to generate and restore heart yang, settling palpitations.
Palpitations with a desire to press on the chest after excessive sweating.
Core pair of a classical formula — Gui Zhi Gan Cao Tang, Shang Han Lun (Zhang Zhongjing)
Clears summerheat and promotes urination while the sweet herb moderates the cold, sliding nature and generates fluids.
Summerheat-dampness with fever, thirst, irritability and scanty dark urine.
Core pair of a classical formula — Liu Yi San, Huang Di Su Wen Xuan Ming Lun Fang (Liu Wansu)
Heat toxin is resolved while lung qi is opened, relieving sore throat.
Core pair of a classical formula — Jie Geng Tang, Shang Han Lun (Zhang Zhongjing)
Nourishing the Heart combined with sweet moderating of acute distress, which calms the spirit in restless organ disorder.
Restless organ disorder (zang zao) with unpredictable weeping and emotional distress.
Core pair of a classical formula — Gan Mai Da Zao Tang, Jin Gui Yao Lue (Zhang Zhongjing)
Evidence Tier
1 RCT · 2 studies on recordRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
1
0 verified · 1 unverified
Other clinical trial
0
Observational / case report
0
In vitro / animal
0
Other / unclassified
1
1 verified · 0 unverified
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Chemical analysis of the Chinese herbal medicine licorice (Gan-Cao): An update review
Comprehensive 2009–2022 review of licorice chemistry, quality evaluation, drug metabolism and pharmacokinetics; catalogues the triterpenoid saponins and flavonoids underlying its activity.
An Extract of Glycyrrhiza glabra (GutGard) Alleviates Symptoms of Functional Dyspepsia: A Randomized, Double-Blind, Placebo-Controlled Study
A standardised low-glycyrrhizin licorice extract significantly reduced functional-dyspepsia symptom scores versus placebo over 30 days, with good tolerability.
⚠ Safety & Contraindications
- Heart conditions
Contraindications
It should not be used together with Sargassum ( hai zao ), Radix Euphorbiae Pekinensis ( jing da ji ), Radix Knoxiae ( hong da ji ), Radix Kansui ( gan sui ), or Flos Genkwa ( yuan hua ). It is not suitable for patients with edema, or fullness due to exuberant dampness.
Source: Xi S, Gong Y. Essentials of Chinese Materia Medica and Medical Formulas. Academic Press/Elsevier, 2017, pp. 330–340.
Side Effects
- Continuous or excessive use can cause sodium and water retention leading to edema and hypertension in 20% of patients.
- Tendency to lower basal metabolic rate and thyroid function.
- Rats given 2.5 g/kg/day orally for 3 months showed reduced weight gain, blood cell count and thymus weight, reversible on withdrawal.
Source: Zhu YP. Chinese Materia Medica: Chemistry, Pharmacology and Applications. Harwood Academic, 1998, p. 567.
⚠ Rule-Based Cautions
These entries come from the deterministic rule tables that gate Verscienta's formula tools — classical pair prohibitions, pregnancy and lactation contraindications, dose ceilings, and drugs outside the Chinese Pharmacopoeia. The botanical-genus entries are different: advisory notes are not part of the safety screen; the Aristolochia genus check is.
Incompatibilities (十八反 / 十九畏)
- 十八反: Gan Cao × Hai Zao — avoid combining with Hai Zao / Sargassum
- 十八反: Gan Cao × Gan Sui — avoid combining with Gan Sui / Euphorbia kansui / Kansui
- 十八反: Gan Cao × Da Ji — avoid combining with Jing Da Ji / Hong Da Ji / Euphorbia pekinensis / Knoxia
- 十八反: Gan Cao × Yuan Hua — avoid combining with Yuan Hua / Genkwa / Daphne genkwa
Breastfeeding
Caution glycyrrhizin exposure to infant; limit dose/duration
Continuous use
Not beyond 28 days at a time — “Not to be used for more than 4 weeks.”
Adults and elderly; not recommended under 18. The figure is for indication 1 (digestive symptoms) at 3–8 g/day of comminuted root (EMA). Source: EMA/HMPC/108399/2024 — European Union herbal monograph on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix (Final – Revision 1, adopted 4 March 2026), §4.2 Duration of use, indication 1. §4.9: overdose has been reported with prolonged use (more than 4 weeks) and/or high intake — water retention, hypokalaemia, hypertension, cardiac rhythm disorders, hypertensive encephalopathy.
A patient's own days on this herb are counted on their patient page (practitioners only).
Historical Texts
Shen Nong Ben Cao Jing
References
- Bensky D, Clavey S, Stöger E. Chinese Herbal Medicine: Materia Medica . 3rd ed. Seattle: Eastland Press (2004)
- Chinese Pharmacopoeia Commission. Glycyrrhizae Radix et Rhizoma . Pharmacopoeia of the People's Republic of China, Vol. I (2020)
- Shang Z, Liu C, Qiao X, Ye M. Chemical analysis of the Chinese herbal medicine licorice (Gan-Cao): An update review . Journal of Ethnopharmacology 299:115686 (2022) [DOI]
- Raveendra KR, et al.. An Extract of Glycyrrhiza glabra (GutGard) Alleviates Symptoms of Functional Dyspepsia: A Randomized, Double-Blind, Placebo-Controlled Study . Evidence-Based Complementary and Alternative Medicine 2012:216970 (2012) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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