Formula Decoction (Tang)

Gan Cao Tang

Licorice Decoction · 甘草汤

An extremely simple one-herb classical formula from the Shang Han Lun, made only with raw licorice root. It is used for mild sore throat caused by Heat affecting the throat, gently clearing Heat and soothing inflammation. If the sore throat does not improve, a second herb (Jie Geng / Platycodon) is added to make Jie Geng Tang.

Origin Shang Han Lun (伤寒论, Treatise on Cold Damage) by Zhang Zhongjing — Eastern Han dynasty (东汉), circa 200 CE
Category Heat-clearing formulas
Therapeutic focus Throat health Immune support
Composition 1 herb
Gan Cao
King
Gan Cao
Explore composition

Educational content • Consult qualified TCM practitioners for diagnosis and treatment

Patterns Addressed

In TCM, symptoms don't appear randomly — they cluster into recognizable patterns of disharmony that reveal what's out of balance in the body. Gan Cao Tang is designed to correct these specific patterns.

Why Gan Cao Tang addresses this pattern

When mild Heat-toxin lodges in the Shaoyin channel and rises to the throat, it causes soreness and slight redness without severe swelling or ulceration. Raw Gan Cao directly clears this Heat-toxin through its slightly cooling nature while its sweet flavour soothes the inflamed throat tissue. This is the classical pattern described in the Shang Han Lun's Shaoyin disease chapter, where Zhang Zhongjing prescribes this single-herb formula for throat pain appearing two to three days into a Shaoyin illness. The mildness of the formula matches the mildness of the pathogenic Heat.

A practitioner would look for one or more of these signs

Sore Throat

Mild sore throat with slight redness, not severely swollen

Throat Redness

Mild redness of the throat without ulceration

Commonly Prescribed For

These conditions can arise from the patterns above. A practitioner would consider Gan Cao Tang when these conditions are specifically caused by those patterns — not for all cases of these conditions.

Arises from: Heat-toxin

TCM Interpretation

In TCM, sore throat can arise from many different patterns. The type addressed by Gan Cao Tang involves mild Heat lodging in the Shaoyin (Lesser Yin) channel system. The Shaoyin channel, connecting the Heart and Kidney, passes through the throat. When a mild pathogenic Heat enters this level, it rises along the channel to affect the throat, causing soreness and slight redness. This is distinct from the more common Wind-Heat sore throat (which involves exterior symptoms like fever and chills) and from the severe Fire-toxin type (which causes pronounced swelling and ulceration). The Shaoyin sore throat tends to appear a few days into an illness and is relatively mild in presentation.

Why Gan Cao Tang Helps

Raw Gan Cao (Sheng Gan Cao) is uniquely suited to this mild presentation. Its slightly cooling nature gently clears the Heat-toxin without being so cold as to injure the Shaoyin's already-fragile balance of Yin and Yang. Its sweet flavour directly moistens and soothes the throat mucosa, providing symptomatic relief. Modern pharmacological research on glycyrrhizin, the main active component in licorice, has confirmed significant anti-inflammatory effects on throat tissue. The formula's simplicity is itself part of its clinical logic: for a mild condition, a gentle, focused intervention is preferred. If the sore throat does not respond within a reasonable time, the classical text instructs adding Jie Geng to form Jie Geng Tang for a stronger therapeutic effect.

Also commonly used for

Pharyngitis

Mild acute pharyngitis with slight redness and pain

Tonsillitis

Early-stage mild tonsillitis before significant swelling develops

Mouth Ulcers

Minor oral ulcerations from Heat-toxin

What This Formula Does

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

Therapeutic focus

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

Throat health Immune support

TCM Actions

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

Clears Heat and resolves toxin Soothes the throat and relieves pain

How It Addresses the Root Cause

TCM doesn't just suppress symptoms — it aims to resolve the underlying imbalance. Here's how Gan Cao Tang works at the root level.

This formula addresses a specific scenario described in the Shaoyin (Lesser Yin) disease chapter of the Shang Han Lun. In this pattern, a mild Heat pathogen lodges in the Shaoyin channel and rises to affect the throat. The Shaoyin channel (which connects the Heart and Kidney) passes through the throat, making it vulnerable when Heat invades this level.

The key point is that this is a mild case. The Heat is not severe enough to cause major swelling, ulceration, or systemic symptoms. There is only slight redness and soreness in the throat, appearing two to three days into a Shaoyin illness. Because the pathogenic Heat is mild and superficial, a single herb with gentle Heat-clearing and toxin-resolving properties is sufficient to address it. The sweet, slightly cool nature of raw licorice can gently clear this Heat while also soothing the throat lining, without the need for strongly bitter or cold herbs that might damage the body's already-vulnerable Yin and Yang.

If this mild approach fails and the throat pain persists, this signals that the Heat is deeper or more substantial, and a second herb (Jie Geng) is added to open and ventilate Lung Qi and direct the formula's action more powerfully to the throat. This stepwise approach reflects Zhang Zhongjing's principle of using the minimum effective intervention.

Formula Properties

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

Overall Temperature

Neutral

Taste Profile

Purely sweet — the sweet flavor soothes the throat, clears Heat-toxin, and harmonizes; raw licorice also carries a slightly cool quality that serves its detoxifying action.

Target Organs

Lungs Stomach Spleen Heart

Channels Entered

Lung Stomach Spleen Heart

Ingredients

1 herb

The herbs that make up Gan Cao Tang, organized by their role in the prescription

King — Main ingredient driving the formula
King — Main ingredient driving the formula
Gan Cao

Gan Cao

Licorice root

Dosage 6 - 12g
Temperature Neutral
Taste Sweet (甘 gān)
Organ Affinity Heart, Lungs, Spleen, Stomach
Preparation Must be used RAW (生甘草 Sheng Gan Cao), not honey-prepared (炙甘草 Zhi Gan Cao). Raw licorice clears Heat and resolves toxin; honey-prepared licorice is warm and tonifies, which would be inappropriate here.

Role in Gan Cao Tang

As the sole ingredient of this formula, raw Gan Cao (Sheng Gan Cao) serves as the King herb. Used in its raw, unprocessed form, it has a slightly cooling quality that allows it to clear Heat-toxin from the throat. Its sweet flavour also moistens and soothes irritated throat tissue, relieving pain directly.
View herb details

Why This Combination Works

How the herbs in Gan Cao Tang complement each other

Overall strategy

The formula's strategy is elegant in its simplicity: address mild Heat-toxin in the throat with a single herb whose sweet, slightly cooling nature can both clear Heat and soothe irritated tissue. Because the pathogenic Heat is mild, a gentle intervention is preferred over aggressive cold or bitter herbs that could further injure the already-weakened Shaoyin.

King herbs

Raw Gan Cao (Sheng Gan Cao) is the sole herb and therefore the King. In its raw form, Gan Cao has a slightly cooling quality that clears Heat-toxin. Its sweet flavour moistens and soothes the throat mucosa, directly relieving soreness and mild inflammation. Classical commentators note that using a single herb makes its therapeutic force more concentrated and focused. As Chen Xiuyuan wrote, raw Gan Cao can clear upper-Burner Fire and regulate the channels.

Notable synergies

As a single-herb formula, there are no internal synergies. However, Gan Cao Tang is designed as the first step of a two-stage treatment: if it proves insufficient, Jie Geng (Platycodon root) is added to create Jie Geng Tang. This pairing is one of the most classic herb combinations in Chinese medicine. Jie Geng opens and ventilates Lung Qi, directing the formula's action upward to the throat, while Gan Cao clears Heat-toxin and soothes the tissue. Together they treat more severe throat Heat than either could alone.

How to Prepare

Traditional preparation instructions for Gan Cao Tang

Take 6–10 g of raw Gan Cao (生甘草, unprocessed licorice root). Place it in a pot with approximately 600 ml (about 3 cups) of water. Bring to a boil, then reduce heat and simmer until the liquid is reduced to roughly 300 ml (about half the original volume). Strain off the dregs.

Divide the decoction into two portions and take warm, twice daily. The classical text specifies taking approximately seven ge (roughly 140 ml) per dose. This is a very simple, single-ingredient decoction and does not require lengthy cooking.

Important: This formula uses raw (生) Gan Cao, not honey-processed (炙) Gan Cao. Raw licorice has stronger Heat-clearing and toxin-resolving properties suited to treating sore throat, whereas honey-processed licorice is warmer and more tonifying.

Common Modifications

How practitioners adapt Gan Cao Tang for specific situations

Added
Jie Geng

3 - 6g; opens and ventilates Lung Qi, directs therapeutic action upward to the throat, and has toxin-resolving and pus-draining properties

This is the classical stepwise approach from the Shang Han Lun itself. Adding Jie Geng transforms this into Jie Geng Tang (Platycodon Decoction). Jie Geng's ability to open Lung Qi and direct herbs upward to the throat significantly strengthens the formula's action on deeper or more stubborn throat Heat.

Related Formulas

Formulas often compared to or combined with Gan Cao Tang, with a side-by-side look at how their compositions differ

Derivative
Neutral 2 herbs Decoction (Tang)

A simple, classical two-herb formula used to soothe sore throats and help the lungs expel phlegm and pus. It combines Platycodon root to open the airways and benefit the throat with raw Licorice root to clear heat, relieve pain, and reduce inflammation. It is the foundational prescription for throat pain in Chinese medicine and is often used as a base to which other herbs are added.

Therapeutic focus
Throat Health Respiratory Health Lung Health

What changed

Jie Geng Tang is Gan Cao Tang plus one herb: Jie Geng (Platycodon, 3-6g). The Shang Han Lun explicitly presents them as a sequential pair: try Gan Cao Tang first for mild Shaoyin throat pain, and if ineffective, upgrade to Jie Geng Tang. The addition of Jie Geng opens Lung Qi and directs the formula's action more powerfully to the throat, making it suitable for more substantial throat Heat with clearer redness and swelling. Jie Geng Tang later became one of the most widely used base formulas for all types of throat conditions.

Composition comparison

Shared (1)
Gan Cao
Only in Gan Cao Tang (0)
—
Only in Jie Geng Tang (1)
Jie Geng
Ban Xia San Ji Tang
Similar indication

How it compares

Ban Xia San Ji Tang (Pinellia Powder and Decoction) also treats Shaoyin throat pain but addresses a Cold pattern rather than a Heat pattern. It uses acrid, warm herbs (Ban Xia, Gui Zhi) to disperse Cold obstruction in the throat. Choose Gan Cao Tang when the throat pain involves redness and Heat signs; choose Ban Xia San Ji Tang when the throat pain involves a cold, obstructed sensation without redness.

Zhu Fu Tang
Similar indication

How it compares

Zhu Fu Tang (Pig Skin Decoction) also treats Shaoyin throat pain but addresses a deficiency pattern with underlying Yin depletion. It nourishes Yin fluids and moistens the throat. Choose Gan Cao Tang for mild Heat-toxin throat pain; choose Zhu Fu Tang when the throat pain accompanies diarrhea, chest fullness, and irritability from Yin deficiency with mild Heat.

Contrasting approach
Warm 2 herbs Decoction (Tang)

A simple but powerful two-herb classical formula used to gently warm the body's core when coldness has settled in the digestive system or lungs. It addresses symptoms like cold hands and feet, nausea, watery sputum, excessive saliva, frequent urination, and a general feeling of deep chill. Originally created by Zhang Zhongjing nearly 1,800 years ago, it remains one of the foundational warming formulas in Chinese medicine.

Therapeutic focus
Respiratory Health Digestive Health Bladder Health Cold Constitution Support

How it compares

Both are simple formulas centred on Gan Cao, but they use different forms and treat opposite conditions. Gan Cao Tang uses raw Gan Cao (Sheng Gan Cao) to clear Heat from the throat. Gan Cao Gan Jiang Tang uses honey-prepared Gan Cao (Zhi Gan Cao) paired with Gan Jiang to warm the Middle Burner Yang. They represent opposite ends of the temperature spectrum: cooling vs. warming. In Shang Han Lun clause 29, they even appear in the same clinical scenario at different treatment stages.

Composition comparison

Shared (1)
Gan Cao
Only in Gan Cao Tang (0)
—
Only in Gan Cao Gan Jiang Tang (1)
Gan Jiang

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

Contraindications

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

Caution

People with existing hypertension or edema. The glycyrrhizin in Gan Cao (licorice) can cause sodium and water retention and raise blood pressure, potentially worsening these conditions.

Caution

People with hypokalemia (low potassium) or those at risk of potassium depletion. Licorice promotes potassium excretion, which can worsen electrolyte imbalances.

Caution

People with kidney disease or heart failure. The mineralocorticoid-like effects of glycyrrhizin can exacerbate fluid retention and electrolyte disturbances in these conditions.

Avoid

Sore throat from excess cold or Yang deficiency without any Heat signs. This formula uses raw (unprocessed) Gan Cao for its cooling, Heat-clearing, and toxin-resolving properties. It is not suitable for throat pain caused by cold pathogen invasion where warming treatment is needed.

Caution

Prolonged use beyond the acute phase. Gan Cao Tang is designed for short-term acute use. Extended consumption of licorice can lead to pseudoaldosteronism with hypertension, edema, and hypokalemia.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

Use with caution during pregnancy. While Gan Cao (licorice) is not classified as a strongly prohibited herb in pregnancy, its active compound glycyrrhizin has been associated in some studies with an increased risk of preterm labor and potential developmental effects. The formula is intended for short-term acute use only (a few days for sore throat), which reduces the risk. Nevertheless, pregnant women should consult a qualified practitioner before use. Deglycyrrhizinated licorice (DGL) is not appropriate here, as the glycyrrhizin contributes to the therapeutic action.

Breastfeeding

Generally considered safe for short-term use during breastfeeding. There is limited data on the transfer of glycyrrhizin and glycyrrhizic acid into breast milk. Because Gan Cao Tang is used only briefly (typically 1–3 days for acute sore throat) and involves a single herb at moderate dosage, the risk is low. However, licorice can potentially affect fluid balance and electrolytes, so nursing mothers should avoid prolonged use. If the infant shows any signs of irritability or digestive upset, discontinue and consult a practitioner.

Children

Gan Cao Tang can be used in children with appropriate dosage reduction. A general guideline is to reduce the adult dose by age: children aged 6–12 may use approximately one-half to two-thirds of the adult dose (3–6 g of raw Gan Cao), and children aged 2–5 may use one-quarter to one-third (2–3 g). Infants under 2 years should only take this formula under direct supervision of a qualified practitioner. The sweet taste of licorice generally makes it palatable for children. As with adults, use should be limited to the short term (a few days) for acute sore throat. Monitor for any signs of fluid retention or digestive disturbance.

Drug Interactions

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

Because Gan Cao Tang is a pure licorice (Glycyrrhiza) decoction, all known licorice-drug interactions apply:

  • Digoxin: Licorice can lower potassium levels, which increases the toxicity of digoxin and may lead to dangerous heart rhythm disturbances. Avoid concurrent use.
  • Antihypertensive medications (ACE inhibitors, ARBs, calcium channel blockers, diuretics): The glycyrrhizin in licorice causes sodium and water retention and raises blood pressure, potentially counteracting these medications.
  • Diuretics (especially potassium-wasting types like furosemide and hydrochlorothiazide): Combined potassium loss from both licorice and diuretics can lead to dangerously low potassium levels (hypokalemia).
  • Corticosteroids (prednisone, dexamethasone, etc.): Licorice may slow the breakdown of corticosteroids and amplify their side effects, including fluid retention and elevated blood pressure.
  • Warfarin and other anticoagulants: Licorice may reduce warfarin's effectiveness by accelerating its metabolism, increasing clotting risk.
  • Cytochrome P450-metabolized drugs: Licorice constituents can inhibit or induce certain CYP450 enzymes (notably CYP3A4 and CYP2C9), potentially altering blood levels of many medications.

Although Gan Cao Tang is used for only a few days at moderate doses, patients on any of these medications should consult their doctor before use.

Usage Guidance

Practical advice for getting the most out of Gan Cao Tang

Best time to take

Twice daily, between meals, taken warm. The warm temperature soothes the throat directly.

Typical duration

Acute use: 1–3 days. If no improvement after this period, the classical text advises switching to Jie Geng Tang.

Dietary advice

While taking Gan Cao Tang for sore throat, avoid spicy, fried, or excessively hot foods that can further irritate the throat and generate more Heat. Cold or iced drinks should also be avoided, as they can impair the Stomach's digestive function. Favor warm, bland, easily digestible foods such as congee (rice porridge), steamed vegetables, and clear soups. Salty foods should be limited, as licorice already promotes sodium retention. Avoid alcohol and smoking, which worsen throat inflammation.

Gan Cao Tang originates from Shang Han Lun (伤寒论, Treatise on Cold Damage) by Zhang Zhongjing — Eastern Han dynasty (东汉), circa 200 CE

Classical Texts

Key passages from the classical Chinese medical texts that first described Gan Cao Tang and its clinical use

《伤寒论》第311条:

少阴病二三日，咽痛者，可与甘草汤；不差，与桔梗汤。

"When a Shaoyin disease of two or three days' duration presents with sore throat, Gan Cao Tang [Licorice Decoction] may be given. If this does not bring improvement, give Jie Geng Tang [Platycodon Decoction]."

《伤寒论》甘草汤方:

甘草二两。右一味，以水三升，煮取一升半，去滓。温服七合，日二服。

"Gan Cao [licorice], two liang. The above one ingredient: decoct with three sheng of water, boil down to one and a half sheng, remove the dregs. Take seven ge warm, twice daily."

Historical Context

How Gan Cao Tang evolved over the centuries — its origins, lineage, and place in the broader tradition of Chinese medicine

Gan Cao Tang is one of the simplest formulas in all of Chinese medicine, consisting of only a single herb: raw Gan Cao (生甘草, unprocessed licorice). It first appears in Zhang Zhongjing's Shang Han Lun (Treatise on Cold Damage), composed around 200 CE during the Eastern Han dynasty. It is prescribed in Article 311 for Shaoyin-stage sore throat, representing one of only two formulas in the entire text that treat this condition (the other being Jie Geng Tang). The text establishes a logical treatment sequence: try the simpler Gan Cao Tang first, and if it does not work, escalate to Jie Geng Tang (which adds Jie Geng/Platycodon to the licorice).

The formula has an alternate name, Wen Ye Tang (温液汤), recorded in Sun Simiao's Qian Jin Yi Fang (Supplement to the Thousand Gold Prescriptions). As a single-herb formula, it beautifully illustrates Zhang Zhongjing's principle of using the minimum number of medicinals needed to address the condition. Commentators throughout history have noted that the Shaoyin sore throat treated by this formula arises from deficiency-Heat: the Kidney Yin is depleted, virtual Fire flares upward, and the throat becomes inflamed. Raw Gan Cao, with its sweet and cool nature, clears Heat, resolves toxins, and soothes the throat. The formula also exemplifies the important processing distinction in Gan Cao: the Shang Han Lun uses raw Gan Cao (生甘草) in only two sore-throat formulas, while nearly all other formulas in the text use honey-processed Gan Cao (炙甘草).

Modern Research

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

1

Topical application of licorice for prevention of postoperative sore throat in adults: A systematic review and meta-analysis (2019)

Kuriyama A, Maeda H. Journal of Clinical Anesthesia. 2019;54:25-32.

This systematic review and meta-analysis of five randomized controlled trials (609 patients) found that topical licorice significantly reduced both the occurrence and severity of postoperative sore throat compared to non-analgesic controls, with no significant adverse events reported. While this studied licorice gargling rather than Gan Cao Tang specifically, it supports the classical use of licorice for throat pain.

PubMed
2

A randomized, double-blind comparison of licorice versus sugar-water gargle for prevention of postoperative sore throat and postextubation coughing (RCT, 2013)

Ruetzler K, Fleck M, Nabecker S, et al. Anesthesia & Analgesia. 2013;117(3):614-621.

This randomized, double-blind trial found that gargling with licorice solution before intubation significantly reduced the incidence of postoperative sore throat compared to sugar water gargle. The study supports the anti-inflammatory and soothing properties of licorice on pharyngeal mucosa, aligning with the traditional indication of Gan Cao Tang for throat pain.

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