Bu Zhong Yi Qi Tang

Bu Zhong Yi Qi Tang (补中益气汤, Bǔ Zhōng Yì Qì Tāng) is a classical Chinese herbal formula first recorded in the Pi Wei Lun (脾胃论, Treatise on the Spleen and Stomach) by Li Dongyuan (李东垣, also known as Li Gao 李杲, 1180–1251 CE), completed in 1232 CE. The formula name literally translates to “Tonify the Middle and Replenish Qi Decoction” — Bu Zhong (补中) means to tonify the Middle Jiao (the Spleen and Stomach), Yi Qi (益气) means to replenish Qi, and Tang (汤) denotes a decoction (liquid preparation formed by boiling herbs).

In the TCM classification system, Bu Zhong Yi Qi Tang belongs to the category of tonifying formulas (bu yi ji, 补益剂) and more specifically to the subcategory of Qi-tonifying formulas (bu qi ji, 补气剂). Its therapeutic strategy encompasses four interconnected actions: tonifying the Spleen and replenishing Qi (bu zhong yi qi, 补中益气), raising Yang Qi (sheng yang ju xian, 升阳举陷), harmonizing the Ying and Wei levels (ying wei he yan, 营卫合沿), and resolving Qi-deficient fever (zhi qi xu fa re, 治气虚发热). These four actions address the complex pathological picture of Spleen Qi deficiency that has progressed to the point of Qi sinking and internal Heat generation.

Within TCM education, Bu Zhong Yi Qi Tang is considered the representative formula of the Yishui School (易水学派) — one of the four great theoretical schools of the Jin-Yuan period (1115–1368 CE). Li Dongyuan, the school's founder, proposed that the root of most diseases lies in damage to the Spleen and Stomach, a concept that diverged from the then-dominant Cold Damage tradition of Zhang Zhongjing. His emphasis on interior deficiency as a primary disease mechanism — rather than externally contracted pathogens — represented a paradigm shift that profoundly influenced all subsequent TCM theory.

In modern TCM clinical practice, the formula is frequently discussed in the context of conditions involving chronic fatigue, organ prolapse (gastric, uterine, rectal), chronic diarrhea, low-grade fever of unknown origin, and post-illness convalescence — all understood through the lens of Spleen Qi deficiency with sinking Qi. It is also widely used in Japan as Hochuekkito (補中益気湯) under the Kampo tradition, where it has been adopted into the national health insurance formulary. It is worth noting that correspondences between TCM patterns and modern biomedical conditions are conceptual analogies, not equivalences. Modern clinical research on this formula, while growing, remains limited and does not establish efficacy for any specific condition.

Li Dongyuan (李东垣, 1180–1251 CE), also known by his given name Li Gao (李杲), was one of the four great physicians of the Jin-Yuan period (金元四大家, Jin Yuan Si Da Jia) alongside Liu Wansu, Zhang Congzheng, and Zhu Danxi. He founded the Yishui School (易水学派), named after his home region in what is now Hebei Province, China. Li Dongyuan's medical philosophy centered on the Spleen and Stomach as the foundation of health — a system he called “nourishing the Earth to generate all things” (wei tian di ben, 脾胃为后天之本). His teacher Zhang Yuansu (张元素) first proposed the idea of器官-specific herb actions, which Li Dongyuan developed into a comprehensive clinical system.

The Pi Wei Lun (脾胃论, Treatise on the Spleen and Stomach) was completed in 1232 CE during a turbulent period of Mongol invasions and widespread famine in northern China. Li Dongyuan observed that the populations suffering from war, displacement, and malnutrition predominantly developed patterns of Spleen and Stomach weakness rather than the externally contracted Cold Damage patterns described by Zhang Zhongjing. He reasoned that when the Spleen (the postnatal source of Qi and Blood) was damaged, the entire body's defensive capacity collapsed, making people susceptible to illness. This insight led him to formulate Bu Zhong Yi Qi Tang as a principal prescription for interior deficiency patterns.

The formula represents a radical departure from earlier clinical strategies. Where Zhang Zhongjing's approach focused on expelling external pathogens and the Shang Han Lun tradition emphasized sweat-inducing, purgative, and harmonizing methods, Li Dongyuan argued that many febrile conditions were not caused by external invasion at all but by internal Qi deficiency. His theory of “sweet warmth removes great heat” (gan wen chu da re, 甘温除大热) proposed that when Spleen Qi is deficient, Yin Fire (yin huo, 阴火) arises from the resulting imbalance — a Heat generated by deficiency rather than excess. This concept was revolutionary for its time and remains one of the most important theoretical contributions in Chinese medical history.

Subsequent generations of physicians expanded upon Li Dongyuan's original framework. In the Ming dynasty (1368–1644 CE), Zhang Jingyue (张景岳) incorporated Li Dongyuan's Spleen-Stomach theory into his own comprehensive system of deficiency-pattern medicine in the Jing Yue Quan Shu (景岳全书). The Qing dynasty physician Luo Guifang (罗国纲) further elaborated the formula's lifting mechanism in his Huo Ren Shu (活人书). Modern TCM textbooks in China, Japan, and Korea consistently include Bu Zhong Yi Qi Tang as a core formula for teaching Qi-tonifying strategies.

In Japan, Bu Zhong Yi Qi Tang (called Hochuekkito in Japanese Kampo, 補中益気湯) has been adopted into the national health insurance formulary and is manufactured by TSUMURA & Co., the largest Kampo pharmaceutical company. Japanese clinical research on the formula — particularly for chronic fatigue, post-operative recovery, gastrointestinal motility disorders, and immune modulation — represents a significant body of modern evidence that complements Chinese clinical studies. The formula is also listed in the Japanese Kampo guidelines (津村順天堂) for indications including general fatigue, night sweats, and poor appetite. This cross-cultural adoption underscores the formula's enduring clinical relevance across East Asian medical traditions.

The following composition reflects classical TCM literature references. Specific dosages are for historical reference and educational context. This is not a dosage recommendation.

The formula reflects Li Dongyuan's clinical strategy of simultaneously tonifying Qi and lifting Yang — the principle of “tonifying the Middle and replenishing Qi” (bu zhong yi qi, 补中益气) combined with “raising Yang and lifting the sunken” (sheng yang ju xian, 升阳举陷). The inclusion of Chen Pi adds a Qi-regulating component, preventing the heavy tonifying herbs from causing stagnation, while Dang Gui ensures that Qi tonification is supported by adequate Blood nourishment.

Classical Dosage Ratios

The original Pi Wei Lun specifies the following quantities in its standard formulation: Huang Qi 1.5 liang (两), Ren Shen 0.6 liang (often noted as 3 qian, 钱三), Bai Zhu 1 liang, Gan Cao 0.6 liang, Dang Gui 0.6 liang, Chen Pi 0.6 liang, Sheng Ma 0.6 liang, Chai Hu 0.6 liang, plus Sheng Jiang 3 slices and Da Zao 3 pieces. Notably, Huang Qi receives the largest dosage, reflecting its role as the Emperor herb for tonifying Spleen and Lung Qi. The relatively even dosages of Ren Shen, Gan Cao, Dang Gui, Chen Pi, Sheng Ma, and Chai Hu reflect their coordinated supporting roles. These classical units do not directly correspond to modern gram measurements and are provided for historical reference only — not as dosage recommendations.

Formula Explanation (Fang Jie, 方解)

The architectural logic of Bu Zhong Yi Qi Tang can be understood through five functional herb groups operating in concert:

• Huang Qi (黄芪) — Emperor Herb: Tonifies Qi and Lifts Yang. Huang Qi is the single most important herb in this formula. With the largest dosage, it tonifies the Spleen and Lung Qi, consolidates the exterior (gu biao, 固表), and raises Yang Qi upward. Li Dongyuan considered Huang Qi the primary herb for restoring the Spleen's lifting function. Its sweet, warm nature aligns perfectly with the “sweet warmth removes great heat” principle, and its Qi-raising property directly addresses the sinking pattern that characterizes the formula's primary indication.
• Ren Shen (人参) + Bai Zhu (白术) + Gan Cao (甘草) — Minister Herbs: The Si Jun Zi Tang Core. These three herbs, when combined with Huang Qi, form the augmented “Four Gentlemen” foundation. Ren Shen strongly tonifies primal Qi (yuan qi, 元气) and supports both Spleen and Lung function. Bai Zhu strengthens the Spleen and dries Dampness, supporting the Spleen's transformative function. Gan Cao (honey-fried, zhi gan cao, 炙甘草) tonifies Spleen Qi and harmonizes the formula, ensuring that all ingredients work in concert. Together, this core quartet provides a powerful Qi-tonifying foundation.
• Dang Gui (当归) — Assistant Herb: Nourishes Blood to Support Qi Generation. In TCM theory, Qi and Blood are mutually generating (qi wei zhi zhi, 气为血之帅; xue wei qi zhi mu, 血为气之母). Dang Gui nourishes Blood, ensuring that Qi tonification has a material substrate to draw upon. Without adequate Blood, Qi tonification alone may be insufficient. Dang Gui also harmonizes the Ying and Wei levels (ying wei, 营卫) and moistens the intestine, counterbalancing the drying tendencies of Bai Zhu and the warming tendency of the formula as a whole.
• Chen Pi (陈皮) — Assistant Herb: Regulates Qi to Prevent Stagnation. A critical design element. With so many tonifying herbs in the formula, there is a risk that they will cause Qi stagnation — the classic problem of “tonifying leads to stagnation” (bu er zhi bi, 补而致痹). Chen Pi, with its aromatic, Qi-regulating properties, ensures that Qi flows freely and that the tonifying herbs are efficiently absorbed and distributed. Its inclusion demonstrates Li Dongyuan's sophisticated understanding of the need to balance tonification with regulation.
• Sheng Ma (升麻) + Chai Hu (柴胡) — Assistant Herbs: Lift Yang Qi Upward. This is the most distinctive feature of Bu Zhong Yi Qi Tang and one of its most brilliant design elements. Sheng Ma and Chai Hu are classically associated with other functions (Sheng Ma with clearing Heat and venting rashes, Chai Hu with harmonizing and resolving stagnation), but in this formula, Li Dongyuan employs them specifically for their ascending properties. They act as “Qi-lifting guides” (sheng yang zhi yin, 升阳之引), working synergistically with Huang Qi to pull sinking Qi back up to its proper position. Without these two herbs, the formula would tonify Qi but might not effectively address the sinking dimension of the pattern.
• Sheng Jiang (生姜) + Da Zao (大枣) — Assistant Herbs: Harmonize and Support. This classic pair (often called the “Sheng Jiang–Da Zao combination”) appears in many Zhang Zhongjing formulas. Sheng Jian harmonizes the Stomach, disperses Cold, and supports the middle Jiao. Da Zao nourishes Blood, tonifies Qi, and harmonizes the formula. Together, they support the Spleen and Stomach and ensure the formula is gentle and well-tolerated.

The overall therapeutic strategy can be summarized as “tonifying the Middle to treat the root, lifting Yang to address the manifestation” (bu zhong wei ben, sheng yang wei biao, 补中为本，升阳为标). This elegant dual approach — replenishing what is deficient (Qi) while lifting what has sunk (Yang) — exemplifies Li Dongyuan's sophisticated clinical reasoning and remains one of the most studied and admired formula architectures in all of TCM education.

These are traditional TCM pattern descriptions, not modern medical diagnoses. They do not constitute treatment recommendations.

• Spleen Qi Deficiency with Sinking Qi (脾气下陷) — The primary pattern for which this formula is classically discussed. Symptoms traditionally associated with this pattern include chronic fatigue, shortness of breath upon exertion, a low and weak voice, reluctance to speak (shao yu lan yan, 少气懒言), general weakness and softness of the limbs (ti juan zhi ruan, 体倦肢软), a sallow or yellowish complexion (mian se wei huang, 面色萎黄), poor appetite (yin shi jian shao, 饮食减少), loose stools (da bian tang bo, 大便溏薄), and a sensation of downward prolapse — which may manifest as gastric prolapse, uterine prolapse, or rectal prolapse (zhong qi xian xia, 中气下陷). On examination, the tongue is typically pale (she dan, 舌淡) with a thin white coating (bai tai, 白苔), and the pulse is characteristically weak (ruo mai, 弱脉), reflecting Qi insufficiency.
• Qi-Deficient Fever (气虚发热) — A unique pattern described by Li Dongyuan in which fever arises from Qi deficiency rather than external pathogenic invasion. Symptoms include persistent low-grade fever, spontaneous sweating (especially upon minimal exertion), thirst with a preference for warm drinks (ke xi re yin, 渴喜热饮), shortness of breath, fatigue that worsens with activity, and a feeling of heat that is not relieved by sweating. The pulse is typically weak and large (ruo da mai, 弱大脉) or deficient and rapid (xu shu mai, 虚数脉). This is the pattern that Li Dongyuan's principle of “sweet warmth removes great heat” was specifically designed to address — the formula treats the fever by tonifying Qi, not by clearing Heat.
• Spleen Qi Deficiency with Chronic Diarrhea — When Spleen Qi is deficient, its transformative function (yun hua, 运化) weakens, leading to incomplete digestion and chronic loose stools. The sinking of Spleen Qi further impairs the ascending and descending dynamics of the gastrointestinal tract, resulting in persistent diarrhea that may worsen with exertion or cold food. Associated symptoms include abdominal distension after eating, a feeling of downward heaviness in the lower abdomen, and fatigue. The tongue is pale with teeth marks (ya yin, 齿痕) and a white coating. The pulse is characteristically weak and slow (ruo huan mai, 弱缓脉).
• Qi Deficiency with Spontaneous Sweating — When Spleen and Lung Qi are deficient, the body's ability to regulate the opening and closing of pores (ying wei bu he, 营卫不和) is impaired, leading to spontaneous sweating without exertion or heat. The sweat is typically light-colored and not accompanied by fever. Associated symptoms include vulnerability to wind and cold (easily catching cold), fatigue, shortness of breath, and a pale complexion. The pulse is weak (ruo mai, 弱脉) and the tongue is pale. In this pattern, Huang Qi's exterior-consolidating function (gu biao, 固表) is particularly important.

Modern research on Bu Zhong Yi Qi Tang has expanded significantly in recent decades, with studies spanning preclinical pharmacology, small clinical trials, and epidemiological investigations. While the evidence base is growing, it remains largely preliminary. The following summaries reflect what individual studies have reported, not established clinical recommendations.

Level 1: Systematic Reviews and Meta-Analyses

A 2017 systematic review by Wang et al., published in Journal of Traditional Chinese Medicine, evaluated Bu Zhong Yi Qi Tang and its modifications for chronic fatigue syndrome. The review identified 18 randomized controlled trials with a total of over 1,400 participants. The authors reported that the formula showed potential benefits for fatigue severity scores compared to placebo or conventional treatments. However, the review noted significant methodological limitations: most trials had small sample sizes (n = 30–80 per arm), inadequate randomization and blinding procedures, and substantial heterogeneity in outcome measures. The quality of evidence was rated as low to very low, and the authors called for larger, rigorously designed RCTs.

Level 2: Individual Randomized Controlled Trials

Several individual RCTs have explored Bu Zhong Yi Qi Tang for specific conditions. A 2019 Chinese RCT by Li et al. evaluated the formula for functional gastroparesis (delayed gastric emptying) in 120 patients, reporting significant improvements in gastric emptying time and symptom scores compared to domperidone alone. A 2018 Japanese RCT by Tanaka et al. investigated Hochuekkito for post-operative fatigue recovery in 80 patients following gastrointestinal surgery, finding that the formula group reported faster fatigue improvement and better appetite recovery. However, these trials were single-center studies with limited sample sizes, and neither has been independently replicated in multi-center settings.

Level 3: Observational Studies and Case Series

Observational data from Japanese Kampo clinical practice provides additional context. A 2016 retrospective study by Imai et al., published in Kampo Medicine, reviewed 245 patients prescribed Hochuekkito for various conditions including chronic fatigue, anorexia, and post-illness convalescence. The study reported improvement rates of approximately 70–80% across all indications based on physician global assessment, with the highest improvement rates observed in fatigue and anorexia. However, observational studies lack control groups and are susceptible to selection bias, regression to the mean, and the placebo effect. These findings should be interpreted as hypothesis-generating rather than evidence of efficacy.

Level 4: Preclinical and Mechanistic Research

Preclinical studies have investigated various pharmacological properties of the individual herbs and the complete formula. A comprehensive review by Du et al. (2019), published in Journal of Ethnopharmacology, summarized research on the chemical constituents and pharmacological activities of Huang Qi (Astragalus membranaceus), reporting immunomodulatory, antioxidant, and adaptogenic effects in animal models. The primary bioactive compounds identified across the formula include astragaloside IV and astragalus polysaccharides (from Huang Qi), ginsenosides (from Ren Shen), atractylenolide (from Bai Zhu), glycyrrhizin (from Gan Cao), ferulic acid and Z-ligustilide (from Dang Gui), hesperidin (from Chen Pi), cimicifugoside (from Sheng Ma), and saikosaponins (from Chai Hu).

Together, these compounds have demonstrated immunomodulatory activity (via regulation of T-cell subsets, NK cell activity, and cytokine profiles), antioxidant effects (scavenging of reactive oxygen species and enhancement of endogenous antioxidant enzymes), anti-inflammatory actions (via suppression of NF-kappa B and TNF-alpha signaling), gastrointestinal motility modulation (via regulation of acetylcholine and nitric oxide pathways), and adaptogenic effects (via modulation of the hypothalamic-pituitary-adrenal axis). A 2020 study by Kim et al. in BMC Complementary Medicine and Therapies also reported that Hochuekkito extract enhanced mitochondrial function in skeletal muscle cells, suggesting a possible mechanism for fatigue reduction. However, these findings cannot be directly extrapolated to the clinical effectiveness of the complete formula in humans.

Overall Evidence Limitations

Key limitations of the existing evidence base include: most clinical studies were conducted in single centers in China or Japan with small sample sizes (typically n = 30–120); many studies used modified versions of the formula rather than the classical composition; blinding was often inadequate or unreported; few studies compared the formula against established standard therapies using non-inferiority designs; long-term safety data are absent; there is a lack of high-quality, large-scale systematic reviews and meta-analyses specifically focused on Bu Zhong Yi Qi Tang; and the gap between preclinical pharmacological findings (often promising) and clinical evidence (often inconclusive) remains substantial. As a result, the evidence does not establish efficacy for any specific condition.