Herb Root (根 gēn)

Gan Cao

Licorice root · 甘草

Glycyrrhiza uralensis Fisch. · Glycyrrhizae Radix et Rhizoma

Also known as: Chinese licorice, Liquorice root, Guó Lǎo (国老),

Gan Cao (Licorice root) plant

Images shown are for educational purposes only

One of the most widely used herbs in all of Chinese medicine, licorice root supports digestion, soothes sore throats, relieves muscle cramps, and helps other herbs in a formula work together harmoniously. The ancient Chinese called it 'The Elder Statesman' (Guó Lǎo) because of its ability to mediate and balance the actions of other medicinal ingredients. It appears in more classical formulas than almost any other herb.

Category Qi-tonifying herbs (补气药)
Therapeutic focus Digestive Health Respiratory Health Throat Health Muscle cramp relief

TCM Properties

Temperature

Neutral

Taste

Sweet (甘 gān)

Channels entered

Heart, Lungs, Spleen, Stomach

Parts used

Root (根 gēn)

Available in our store
View in Store
From $23.00

Educational content • Consult qualified TCM practitioners for diagnosis and treatment

What This Herb Does

Every herb has a specific set of actions — here's what Gan Cao does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Gan Cao is primarily used to support these areas of health:

Digestive Health Respiratory Health Throat Health Muscle cramp relief

TCM Actions

In TCM terminology, these are the specific therapeutic actions that Gan Cao performs to restore balance in the body:

Tonifies the Middle and Augments Qi Clears Heat and Resolves Toxicity Expels Phlegm and Stops Cough Relaxes Spasms and Relieves Urgency Harmonizes Other Herbs

How these actions work

'Tonifies the Spleen and augments Qi' means Gān Cǎo strengthens the digestive system and boosts the body's vital Qi. Because it is sweet in taste and enters the Spleen and Stomach channels, it naturally supplements the middle Qi that the Spleen produces. This makes it useful for tiredness, poor appetite, loose stools, and shortness of breath that come from a weakened digestive system. In the honey-prepared form (Zhì Gān Cǎo), this tonifying action is significantly enhanced.

'Clears Heat and resolves toxins' applies specifically to the raw, unprocessed form (Shēng Gān Cǎo). Despite being neutral in temperature overall, raw licorice has a slightly cooling quality that allows it to clear Heat-toxins. This is why it is used for sore throat, skin abscesses, boils, and mouth ulcers, often paired with herbs like Jīn Yín Huā (honeysuckle) or Jú Gěng (platycodon). It also helps neutralize the toxicity of other herbs and even some ingested poisons.

'Expels Phlegm and stops cough' reflects licorice's ability to moisten the Lungs and help clear Phlegm from the airways. It enters the Lung channel and is sweet and moistening, making it suitable for coughs of almost any type, whether from cold, heat, dryness, or deficiency.

'Relaxes spasm and stops pain' (缓急止痛 huǎn jí zhǐ tòng) means the herb can relieve cramping and spasmodic pain, particularly in the abdomen and limbs. The classical example is Sháo Yào Gān Cǎo Tāng (Peony and Licorice Decoction), where licorice works with white peony to ease muscle cramps and leg spasms.

'Moderates and harmonizes other herbs' is perhaps licorice's most famous role. Its sweet, gentle nature buffers the harsh or toxic properties of other herbs in a formula, softens strong flavours, and helps different ingredients work together smoothly. This is why classical Chinese physicians nicknamed it Guó Lǎo ('The Elder Statesman') and why the saying goes 'nine out of ten prescriptions contain Gān Cǎo.'

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony. Gan Cao is used to help correct these specific patterns.

Why Gan Cao addresses this pattern

Gān Cǎo is sweet in taste and enters the Spleen and Stomach channels, making it a natural supplement for weakened digestive Qi. When the Spleen fails to properly transform food into Qi and Blood, symptoms like fatigue, poor appetite, and loose stools appear. Gān Cǎo's sweet, tonifying nature directly replenishes the Spleen's Qi, and its gentle quality makes it safe even for patients who are quite depleted. In this pattern, the honey-processed form (Zhì Gān Cǎo) is preferred for its stronger warming and tonifying effect.

A practitioner would look for one or more of these signs

Eye Fatigue

Tiredness and lack of stamina from weakened digestive function

Poor Appetite

Reduced desire to eat

Loose Stools

Soft or unformed bowel movements

Shortness Of Breath

Mild breathlessness on exertion

Commonly Used For

These are conditions where Gan Cao is frequently used — but only when they arise from the specific patterns it addresses, not in all cases

Arises from: Spleen Qi Deficiency

TCM Interpretation

In TCM, peptic ulcers are most commonly understood as a pattern of Spleen and Stomach disharmony. When Spleen Qi is deficient, the Stomach loses its protective function and becomes vulnerable to damage. This may be compounded by emotional stress causing Liver Qi to 'invade' the Stomach, or by dietary irregularity generating Dampness-Heat. The resulting epigastric pain, acid reflux, and poor digestion all reflect the Stomach's inability to 'ripen and rot' food properly when Qi is insufficient.

Why Gan Cao Helps

Gān Cǎo directly addresses peptic ulcers in two complementary ways. First, as a sweet, Spleen-tonifying herb, it strengthens the digestive Qi that keeps the Stomach functioning normally. Second, its sweet, moistening quality has a soothing effect on the Stomach lining. Modern pharmacological research has confirmed that glycyrrhizin and related compounds promote mucus formation in the stomach and have anti-inflammatory properties. Historically, the drug carbenoxolone, derived from licorice's active compound glycyrrhetinic acid, was used specifically to treat gastric and duodenal ulcers.

Also commonly used for

Hypochondrial Pain That Is Worse On Coughing And Breathing

Various types of cough, both productive and dry

Severe Heart Palpitations

Arrhythmias and functional heart rhythm disturbances (with Zhì Gān Cǎo)

Mouth Ulcers

Recurrent aphthous stomatitis

Chronic Gastritis

Chronic inflammation of the stomach lining

Eye Fatigue

Chronic fatigue from Spleen Qi Deficiency

Bronchitis

Acute and chronic bronchitis with cough and phlegm

Keratitis

Various inflammatory skin conditions including eczema

Herb Properties

Every herb has an inherent temperature, taste, and affinity for specific channels — these properties determine how it interacts with the body

Temperature

Neutral

Taste

Sweet (甘 gān)

Channels Entered

Heart Lungs Spleen Stomach

Parts Used

Root (根 gēn)

Dosage & Preparation

These are general dosage guidelines for Gan Cao — always follow your practitioner's recommendation, as dosages vary based on the formula and your individual condition

Standard dosage

2-10g

Maximum dosage

Up to 30g in acute situations (e.g. severe poisoning, acute sore throat), for short-term use under practitioner supervision. For daily formulas, do not exceed 10g without specific clinical justification.

Dosage notes

Use lower doses (2-6g) when Gan Cao serves as an envoy herb to harmonise a formula or moderate harsh properties of other herbs. Use moderate doses (6-10g) for tonifying Spleen Qi, relieving cough, or alleviating pain. Higher doses (10-30g) may be used short-term for clearing Heat-toxins (raw Gan Cao) or in acute poisoning situations. Raw Gan Cao (Sheng Gan Cao) is preferred for clearing Heat, resolving toxins, and soothing the throat. Honey-roasted Gan Cao (Zhi Gan Cao) is preferred for tonifying Qi, nourishing the Heart, and harmonising the Middle Jiao. When using doses above 10g or for periods longer than 4-6 weeks, monitor blood pressure and serum potassium. Elderly patients and those with pre-existing cardiovascular or renal conditions require more conservative dosing.

Preparation

No special decoction handling required. Gan Cao is decocted normally with other herbs. However, the choice between raw and honey-roasted forms is clinically important: use raw (Sheng Gan Cao) for clearing Heat and toxins; use honey-roasted (Zhi Gan Cao) for tonifying Qi and harmonising.

Processing Methods

In TCM, the same herb can be prepared in different ways to change its effects — here's how processing alters what Gan Cao does

Processing method

Stir-fried with honey (蜜炙). The sliced root is mixed with a measured amount of refined honey diluted with a small amount of water, allowed to absorb, then stir-fried over a gentle flame until it turns golden-yellow to deep yellow and is no longer sticky to the touch.

How it changes properties

Honey-processing shifts the herb's temperature from neutral toward slightly warm. It greatly enhances the Qi-tonifying and Spleen-strengthening action, and adds the ability to tonify Heart Qi and restore the pulse (益气复脉). The Heat-clearing and toxin-resolving actions of raw licorice are significantly reduced or lost. The honey further increases the moistening quality.

When to use this form

Use Zhì Gān Cǎo when the goal is to tonify Qi, especially Spleen and Heart Qi. Key indications include fatigue, poor appetite, loose stools from Spleen Qi Deficiency, and irregular heartbeat (palpitations with a knotted or intermittent pulse). This is the form used as the King herb in Zhì Gān Cǎo Tāng (Honey-Prepared Licorice Decoction) for heart palpitations and arrhythmia.

Common Herb Pairs

These ingredients are traditionally combined with Gan Cao for enhanced therapeutic effect

Bai Shao
Bai Shao Bái Sháo 12g : Gān Cǎo 6g (2:1, with Bái Sháo as the larger dose)

Gān Cǎo (sweet) and Bái Sháo (sour) combine to 'generate Yin through sour and sweet flavours' (酸甘化阴). Together they nourish Blood and Body Fluids, relax the sinews, and relieve spasmodic pain far more effectively than either herb alone. This is one of the most iconic herb pairs in Chinese medicine.

When to use: Muscle cramps (especially calf cramps), abdominal cramping pain, menstrual cramps, and any spasmodic condition caused by insufficient Blood or Yin failing to nourish the sinews.

Jie Geng
Jie Geng Jú Gěng 6g : Gān Cǎo 6g (1:1)

Jú Gěng opens and ventilates the Lung Qi and directs herbs upward to the throat, while Gān Cǎo clears Heat-toxins and soothes the throat lining. Together they clear the throat, resolve toxin, and stop pain. This pair forms the complete formula Jú Gěng Tāng (Platycodon Decoction).

When to use: Sore throat, tonsillitis, pharyngitis, early-stage lung abscess (lung carbuncle) with cough and thick phlegm.

Gan Jiang
Gan Jiang Zhì Gān Cǎo 12g : Gān Jiāng 6g (2:1, licorice is the larger dose)

Gān Jiāng (dry ginger) warms the middle and disperses cold, while Zhì Gān Cǎo (honey-processed licorice) tonifies Spleen Qi and moderates ginger's drying heat. Together they warm and restore the Spleen and Lung Yang through the principle of 'pungent and sweet generating Yang' (辛甘化阳). This pair forms the formula Gān Cǎo Gān Jiāng Tāng.

When to use: Spleen-Lung Yang Deficiency with cold limbs, profuse thin sputum, vomiting of clear fluids, and loose stools. Also used to rescue middle-burner Yang after excessive sweating.

Lai Fu Zi
Lai Fu Zi Fù Zǐ 9-15g : Gān Cǎo 6g (as part of Sì Nì Tāng, which also includes Gān Jiāng)

Fù Zǐ powerfully restores collapsed Yang, while Gān Cǎo both supports the Qi and significantly reduces the toxicity of Fù Zǐ's aconitine alkaloids. Research has shown that glycyrrhizic acid binds with aconitine to form insoluble compounds, directly lowering the toxic load.

When to use: Yang collapse with cold extremities, weak pulse, and diarrhea. This pair appears in Sì Nì Tāng (Frigid Extremities Decoction) as a life-saving combination.

Key Formulas

These well-known formulas feature Gan Cao in a prominent role

Zhi Gancao Tang 炙甘草湯 King

The definitive showcase of honey-processed licorice's Heart Qi-tonifying action. Zhì Gān Cǎo serves as King at 12g, demonstrating its unique ability to tonify Heart Qi and restore the pulse. The formula treats palpitations with an irregular (knotted or intermittent) pulse due to Qi and Yin Deficiency. From the Shāng Hán Lùn.

Gan Cao Gan Jiang Tang 甘草乾薑湯 King

Another Shāng Hán Lùn formula where Zhì Gān Cǎo is King at double the dose of Gān Jiāng. This two-herb formula demonstrates the 'pungent-sweet generating Yang' principle to warm the Spleen and Lung Yang, treating cold extremities, thin sputum, and Yang Deficiency after excessive sweating.

Ban Xia Xie Xin Tang 半夏泻心汤 King

Named after Gān Cǎo, this Shāng Hán Lùn formula uses a large dose of Zhì Gān Cǎo as King to tonify the deficient Stomach Qi that underlies the condition. It treats epigastric distention (a 'pì' pattern) with diarrhea, borborygmus, and irritability from a combination of Stomach Qi weakness and residual Heat.

Shao Yao Gan Cao Tang 芍藥甘草湯 Deputy

This elegant two-herb formula from the Shāng Hán Lùn perfectly demonstrates Gān Cǎo's spasm-relieving action. Paired with Bái Sháo (white peony), it creates the classical 'sour-sweet generating Yin' combination to relax the sinews, relieve cramping, and stop pain. It remains one of the most frequently used formulas for muscle cramps.

Comparable Ingredients

These ingredients have overlapping uses — here's how to tell them apart

Huang Qi
Gan Cao vs Huang Qi

Both tonify Spleen Qi, but Huáng Qí is warm, raises Yang, consolidates the exterior against sweating, and promotes tissue healing. It is a much stronger Qi tonic used in larger doses. Gān Cǎo is milder and neutral, with the unique additions of clearing toxins, relieving spasm, harmonizing other herbs, and stopping cough. Choose Huáng Qí for significant Qi Deficiency with Yang sinking or immune weakness. Choose Gān Cǎo when you need gentle tonification with harmonizing and detoxifying benefits.

Dang Shen
Gan Cao vs Dang Shen

Both are sweet Qi tonics that strengthen the Spleen, but Dǎng Shēn is primarily a straightforward Qi-tonifying herb with some Blood-nourishing action, used as a gentler substitute for Rén Shēn (ginseng). Gān Cǎo is less focused on pure Qi tonification and has a broader profile that includes clearing toxins, relieving cramps, soothing the throat, and moderating other herbs. Dǎng Shēn is chosen when direct Qi tonification is the priority. Gān Cǎo is chosen for its multifaceted supporting and harmonizing roles.

Da Zao
Gan Cao vs Da Zao

Both are sweet, tonify the Spleen, and are commonly used as harmonizing agents in formulas. Dà Zǎo (jujube date) is warmer and better at nourishing Blood and calming the spirit, making it more suitable for Blood Deficiency with anxiety or poor sleep. Gān Cǎo is neutral and excels at clearing toxins, relieving spasm, and moderating the harsh properties of other herbs. In many classical formulas, both appear together for a combined harmonizing effect.

Common Substitutes & Adulterants

Related species and common adulterations to be aware of when sourcing Gan Cao

Three species are officially listed in the Chinese Pharmacopoeia as sources of Gan Cao: Glycyrrhiza uralensis (Ural licorice, the primary species), Glycyrrhiza inflata (inflated-fruit licorice), and Glycyrrhiza glabra (smooth-fruit licorice). Of these, G. uralensis is considered the standard and highest quality. G. inflata has a less powdery cross-section and sometimes a slightly bitter taste. G. glabra has a firmer texture with fewer visible fissures. On the market, thin, lightweight, pithy roots from immature plants or poor growing conditions are sometimes mixed with genuine material. Cultivated Gan Cao (3-4 years) may have lower glycyrrhizin content compared to wild-harvested roots. In the international market, licorice root may come from many Glycyrrhiza species not used in TCM, which have different chemical profiles and therapeutic properties.

Educational content — always consult a qualified healthcare provider or TCM practitioner before using any herb.

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Gan Cao

Non-toxic

Gan Cao is classified as non-toxic in the Chinese Pharmacopoeia and is one of the safest herbs in the materia medica. However, its main active compound glycyrrhizin can cause pseudoaldosteronism when consumed in high doses or over prolonged periods. The mechanism involves glycyrrhetinic acid (a metabolite of glycyrrhizin) inhibiting 11β-hydroxysteroid dehydrogenase type 2 in the kidneys, which allows cortisol to activate mineralocorticoid receptors. This results in sodium and water retention, potassium loss, elevated blood pressure, and edema. The amount of glycyrrhizin estimated to produce these side effects in normal subjects is 0.7-1.4g, corresponding to roughly 10-14g of crude herb taken daily over an extended period. These effects are dose-dependent and reversible upon discontinuation. Risk factors include older age, pre-existing hypertension, constipation, hypoalbuminemia, and concurrent use of potassium-depleting medications.

Contraindications

Situations where Gan Cao should not be used or requires extra caution

Caution

Edema or fluid retention conditions. Gan Cao's sweet flavour can promote dampness and fluid retention, and its glycyrrhizin content causes sodium and water retention through pseudoaldosteronism. Use is contraindicated in patients with existing edema.

Caution

Hypertension. The glycyrrhizin metabolite glycyrrhetinic acid inhibits 11-beta-hydroxysteroid dehydrogenase type 2 (11β-HSD2) in the kidneys, leading to mineralocorticoid-like effects that raise blood pressure. Avoid prolonged use or high doses in hypertensive patients.

Avoid

Hypokalemia or patients at risk of low potassium (e.g. those on potassium-depleting diuretics). Gan Cao promotes potassium excretion through its pseudoaldosterone effect, which can cause dangerously low potassium levels, cardiac arrhythmias, and muscle weakness.

Avoid

Congestive heart failure or severe kidney disease. Sodium and water retention caused by glycyrrhizin can worsen cardiac and renal congestion.

Caution

Dampness with abdominal bloating and fullness (湿盛中满). Gan Cao's sweet, moistening nature can worsen dampness accumulation and cause distension. Classical texts warn that it can 'assist dampness and obstruct Qi, causing abdominal fullness.'

Caution

Nausea and vomiting due to excess dampness. The sweet, cloying nature of Gan Cao can aggravate these symptoms.

Avoid

Patients on digoxin or other cardiac glycosides. Gan Cao-induced hypokalemia increases the toxicity of cardiac glycosides and may precipitate dangerous arrhythmias.

Caution

Long-term use at high doses (exceeding 10g daily for more than 4-6 weeks) without medical supervision. Prolonged use increases the risk of pseudoaldosteronism with hypertension, hypokalemia, and edema.

Classical Incompatibilities

Traditional Chinese pharmacological incompatibilities — herbs or substances to avoid combining with Gan Cao

Gan Cao is incompatible with Gan Sui (甘遂, Radix Kansui), Da Ji (大戟, Radix Euphorbiae Pekinensis / Radix Knoxiae), Yuan Hua (芫花, Flos Genkwa), and Hai Zao (海藻, Sargassum) according to the Eighteen Incompatibilities (十八反). The classical mnemonic verse states: '藻戟遂芫俱战草' (Seaweed, Euphorbia, Kansui, and Genkwa all war against Cao). This prohibition was first recorded in the Ben Cao Jing Ji Zhu by Tao Hongjing, was later formalised as a verse in the Ru Men Shi Qin, and is codified in the Chinese Pharmacopoeia. Note: some historical formulas (e.g. Gan Sui Ban Xia Tang from the Jin Gui Yao Lue, Hai Zao Yu Hu Tang) deliberately combine Gan Cao with its 'incompatible' partners for specific therapeutic purposes, but this requires expert judgement and is not standard practice.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

Use with caution during pregnancy. While Gan Cao is not classified as a prohibited herb in pregnancy and is included in many classical formulas used during pregnancy at low doses, modern research suggests potential concerns. Glycyrrhizin may affect cortisol metabolism through inhibition of 11β-HSD2, and there are reports suggesting that high licorice intake during pregnancy may be associated with preterm labour and adverse developmental outcomes. Standard low doses (2-6g) as part of a balanced formula for short periods are generally considered acceptable under professional guidance. Avoid high doses or prolonged independent use during pregnancy.

Breastfeeding

No specific prohibition during breastfeeding at standard doses. Glycyrrhizin and its metabolites may transfer into breast milk, and the potential for mineralocorticoid-like effects (fluid retention, blood pressure changes) in the nursing infant has not been well studied. Low doses within balanced formulas are generally regarded as acceptable for short-term use. Prolonged high-dose use should be avoided. Monitor the infant for signs of fluid retention or irritability.

Children

Gan Cao is widely used in paediatric formulas at reduced doses appropriate to the child's age and weight. As a general guide, children under 6 may use one-third to one-half the adult dose, while children 6-12 may use one-half to two-thirds. However, because Gan Cao can promote fluid retention and affect electrolyte balance, prolonged use at higher doses should be avoided in children. Monitor for signs of edema or blood pressure changes with extended use.

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Gan Cao

Cardiac glycosides (digoxin): Gan Cao-induced hypokalemia significantly increases the risk of digoxin toxicity and cardiac arrhythmias. Concurrent use should be avoided or carefully monitored with regular potassium level checks.

Thiazide and loop diuretics (hydrochlorothiazide, furosemide): Both Gan Cao and these diuretics promote potassium loss. Combined use increases the risk of severe hypokalemia. Monitoring of electrolytes is essential.

Antihypertensive medications: Gan Cao's sodium- and water-retaining properties can directly counteract the effects of antihypertensive drugs, reducing their efficacy and worsening blood pressure control.

Corticosteroids (prednisone, prednisolone): Glycyrrhizin inhibits the breakdown of corticosteroids, potentiating their effects and increasing the risk of corticosteroid side effects including adrenal suppression, hyperglycaemia, and immunosuppression.

Warfarin and anticoagulants: Hypokalemia from Gan Cao may alter cardiac rhythm and complicate anticoagulant therapy. The interaction is indirect but clinically relevant.

Oral hypoglycaemic agents and insulin: Glycyrrhizin may affect blood glucose levels. Patients using diabetes medications should monitor blood sugar closely when taking Gan Cao.

CYP3A4 substrates: Licorice root extract and glabridin have been shown to inhibit CYP3A4, a major drug-metabolising enzyme, potentially increasing blood levels of many medications metabolised by this pathway.

Dietary Advice

Foods and dietary considerations when taking Gan Cao

When taking Gan Cao, especially at higher doses or for extended periods, favour potassium-rich foods such as bananas, sweet potatoes, leafy greens, and beans to help offset its potassium-depleting effect. Reduce salt intake, as Gan Cao already promotes sodium retention. Avoid excessive consumption of other sweet or damp-producing foods (rich dairy, greasy fried foods, excessive sugar) that may compound Gan Cao's tendency to generate dampness. Classical sources note that Hai Zao (seaweed/sargassum) should not be consumed with Gan Cao due to their incompatibility.

Botanical Description

Physical characteristics and morphology of the Gan Cao source plant

Glycyrrhiza uralensis Fisch. (Ural licorice) is a perennial herbaceous legume of the Fabaceae family, growing 50 to 120 cm tall. The stems are erect and densely covered with white short hairs and glandular trichomes. The leaves are odd-pinnately compound with 7 to 17 leaflets that are ovate to elliptical, with both surfaces densely covered in yellowish-brown glandular dots and fine hairs.

Flowers appear in axillary racemes from June to August, with butterfly-shaped corollas in pale blue-purple, purple-red, white, or yellow. The fruit pods are curved into a sickle or ring shape, densely clustered into a ball, and covered with knob-like protuberances and bristly glandular hairs, ripening from July to October.

The medicinal part is the thick, stout root and rhizome, which has a brownish outer bark and a characteristically sweet taste. The root system is deep, sometimes reaching 1 to 1.5 metres. The plant thrives in arid and semi-arid environments, including sandy soils, desert margins, river banks, and alkaline land across northern China, Mongolia, and Central Asia. Two related species are also used medicinally: Glycyrrhiza inflata Bat. (inflated-fruit licorice) and Glycyrrhiza glabra L. (smooth-fruit licorice).

Sourcing & Harvesting

Where Gan Cao is sourced, when it's harvested or collected, and how to assess quality

Harvesting season

Spring and autumn, with autumn harvest preferred. Roots are best at 3-4 years of growth.

Primary growing regions

The premier terroir (道地药材) region for Gan Cao is Inner Mongolia (especially the Alashan League and Ordos area), often called 'Liang Wai Cao' (梁外草). Other major production areas include Gansu, Ningxia, and Xinjiang. Inner Mongolia, Gansu, and Ningxia produce the highest quality, while Xinjiang has the largest total output. Historically, the herb from Inner Mongolia's western arid desert-margin grasslands has been most prized. Within the trade, herb from western regions is called 'Xi Cao' (西草) and from eastern regions 'Dong Cao' (东草). Glycyrrhiza inflata and Glycyrrhiza glabra are mainly produced in Xinjiang and Gansu.

Quality indicators

Good quality Gan Cao root is cylindrical, long, and relatively thick (0.6-3.5 cm diameter). The outer skin should be tight-fitting (not loose or peeling), reddish-brown in colour, and finely textured. The cross-section should be yellowish-white with a clear visible cambium ring and distinct radial lines, showing a floury (powdery) texture. The herb should feel solid and heavy when held. The taste should be distinctly sweet with a characteristic subtle flavour. The traditional saying is: 'skin fine and red, solid in texture, cross-section yellowish-white, powdery, and sweet in taste' (皮细色红、质坚实、断面色黄白、粉性足). The best grade, historically called 'Fen Cao' (粉草, powdery licorice), has a large diameter and tight cross-section with clear markings. Avoid roots that are thin, light, pithy, fibrous without powder, dark-coloured internally, or bitter-tasting.

Classical Texts

Key passages from the classical Chinese medical texts that describe Gan Cao and its therapeutic uses

Shen Nong Ben Cao Jing (《神农本草经》, Divine Farmer's Classic of Materia Medica)

Original: 味甘平。主五脏六腑寒热邪气，坚筋骨，长肌肉，倍力，金创，解毒。久服轻身延年。

Translation: Sweet in flavour, neutral in nature. It governs cold and heat evil Qi of the five Zang and six Fu organs, strengthens sinews and bones, promotes flesh growth, doubles strength, treats wounds, and resolves toxins. Long-term use lightens the body and extends life.

Ben Cao Jing Ji Zhu (《本草经集注》, Tao Hongjing, Southern Dynasties)

Original: 此草最为众药之主，经方少有不用者。

Translation: This herb is the foremost leader among all medicines; classical formulas rarely go without it.

Yao Xing Ben Cao (《药性本草》, Zhen Quan, Tang Dynasty)

Original: 诸药中甘草为君，治七十二种乳石毒，解一千二百般草木毒，调和众药有功，故有国老之号。

Translation: Among all herbs, Gan Cao is the sovereign. It treats 72 types of mineral toxicity and resolves 1,200 kinds of herbal poisons. For its merit in harmonising all medicines, it bears the title 'National Elder' (Guo Lao).

Ben Cao Gang Mu (《本草纲目》, Li Shizhen, Ming Dynasty)

Original: 甘草资全土德，协和群品，有元老之功，善治百邪，得王道之化。赞帝力而人不知，欲神功而己不与，可谓药中之良相也。

Translation: Gan Cao embodies the full virtue of Earth, harmonises all substances, and possesses the merit of a Grand Elder. It skillfully governs a hundred evils and acts through the Way of the Benevolent King. It supports the sovereign's power yet no one notices; it achieves wondrous results yet claims no credit. It may be called the Worthy Minister among medicines.

Historical Context

The history and evolution of Gan Cao's use in Chinese medicine over the centuries

Gan Cao has been used in Chinese medicine for over 2,500 years. It is listed as a 'superior' (上品) herb in the Shen Nong Ben Cao Jing, the earliest known Chinese materia medica, where superior herbs are defined as non-toxic substances that can be taken long-term. It holds the distinction of being one of the most frequently used herbs across all of classical Chinese medicine, appearing in an extraordinary number of formulas. The classical saying goes: 'Ten formulas, nine contain Cao' (十方九草). Tao Hongjing (Southern Dynasties period) praised it as the 'chief among all medicines,' noting that classical formulas rarely omit it.

The herb earned the honorary title 'Guo Lao' (国老, National Elder), a term originally reserved for the retired imperial tutor. This name reflects Gan Cao's role as a trusted, dignified mediator. Just as the National Elder could harmonise court politics without holding direct power, Gan Cao harmonises and moderates the actions of other herbs in a formula. Li Shizhen in the Ben Cao Gang Mu extended this metaphor, calling it 'the Worthy Minister among medicines.' The name 'Gan Cao' itself simply means 'sweet herb,' referring to its remarkably sweet taste. Classical aliases include 'Mi Gan' (蜜甘, honey-sweet), 'Mei Cao' (美草, beautiful herb), and 'Mi Cao' (蜜草, honey herb). The Greek-derived botanical name Glycyrrhiza also means 'sweet root' (from glykos + rhiza).

The distinction between raw Gan Cao (生甘草, Sheng Gan Cao) and honey-roasted Gan Cao (炙甘草, Zhi Gan Cao) is a longstanding practice. Raw Gan Cao clears Heat and resolves toxins, while honey-processed Gan Cao is warmer and more strongly tonifies Qi and harmonises the Middle Jiao. Zhang Zhongjing used both forms extensively across the Shang Han Lun and Jin Gui Yao Lue, making Gan Cao one of the most central herbs in classical formula medicine.

Modern Research

5 published studies investigating the pharmacological effects or clinical outcomes of Gan Cao

1

Systematic review and meta-analysis: Metabolic changes after licorice consumption (2018)

Luís Â, Domingues F, Pereira L. Phytomedicine, 2018, 39: 17-24.

A meta-analysis of 26 clinical trials (985 participants) found that licorice consumption significantly reduced body weight and BMI, but also caused a significant increase in diastolic blood pressure, consistent with its known sodium-retaining effects. The authors concluded that hypertensive patients should avoid licorice.

DOI
2

Systematic review and meta-analysis: Licorice ingestion, hypertension and hypokalemia (2017)

Penninkilampi R, Eslick EM, Eslick GD. Journal of Human Hypertension, 2017, 31(11): 699-707.

A systematic review and meta-analysis of 18 clinical trials (337 participants) found a dose-dependent association between consistent licorice ingestion and increased blood pressure as well as decreased plasma potassium, confirming the clinical significance of the pseudoaldosteronism risk.

DOI
3

Narrative review: Clinical risk factors of licorice-induced pseudoaldosteronism (2021)

Yoshino T, Shimada S, Homma M, Makino T, Mimura M, Watanabe K. Frontiers in Nutrition, 2021, 8: 719197.

This review summarised the pathophysiology of licorice-induced pseudoaldosteronism, explaining how glycyrrhizin metabolites (particularly 18β-glycyrrhetyl-3-O-sulfate and glycyrrhetinic acid) inhibit 11β-HSD2 in the kidneys. Key risk factors identified include high dosage, long-term use, older age, constipation, low albumin, and concurrent medications.

DOI
4

Systematic review and meta-analysis of RCTs: Licorice and liver function in primary liver disease (2024)

Phytotherapy Research, 2024, 38(9): 4614-4627.

A meta-analysis of 15 RCTs involving 1,367 participants evaluated the effects of licorice formulations on liver function in patients with primary liver disease. The analysis found that licorice preparations, alone or combined with other herbs, significantly improved liver enzyme levels (ALT, AST, TBiL) compared to control groups.

DOI
5

Comprehensive narrative review: Liquorice toxicity (2023)

Ceccuzzi G, Rapino A, Perna B, et al. Nutrients, 2023, 15(18): 3866.

A thorough review of 104 published cases of licorice toxicity found that hypertension and hypokalemia were the most prevalent features. While there was no significant mortality rate, licorice toxicity often required hospitalisation. The authors called for greater public awareness of the risks of excessive licorice consumption.

DOI

Research on individual TCM herbs is growing but still limited by Western clinical trial standards. These studies provide emerging evidence and should be considered alongside practitioner expertise.