Four Levels (Wen Bing)
A diagnostic framework created by Ye Tianshi for analyzing febrile diseases caused by warm pathogens, tracking disease progression through four levels: Wei (Defensive), Qi, Ying (Nutritive), and Xue (Blood), from superficial to deep, mild to severe.
Wèi Qì Yíng Xuè Biàn Zhèng
Four Levels (Wei-Qi-Ying-Xue)
Educational content · Consult qualified TCM practitioners for diagnosis and treatment
Overview
The Four Levels (卫气营血辨证, Wèi Qì Yíng Xuè Biàn Zhèng) is a diagnostic framework specifically designed for understanding and treating diseases caused by warm pathogens—what we might today recognize as acute infectious or febrile diseases. Think of it as a roadmap showing how an infection can progress through your body if left unchecked.
While the older Six Stages theory from the Shang Han Lun focused on diseases caused by cold pathogens, the Four Levels addresses heat-type illnesses—conditions marked by fever, inflammation, and the body's fight against infectious agents. The framework divides disease progression into four distinct levels, moving from the body's surface inward: Wei (Defensive level—the body's first line of defense), Qi (where internal heat builds up), Ying (Nutritive level—affecting deeper nourishment and the mind), and Xue (Blood level—the deepest and most serious stage).
This system remains highly relevant today. During outbreaks of viral illnesses, including COVID-19, practitioners have used Four Levels theory to guide treatment strategies, adjusting herbal formulas based on which level the disease has reached. The framework helps practitioners understand not just where the disease is now, but where it's heading—allowing for proactive treatment.
Historical Context
The Four Levels was created by Ye Tianshi (叶天士, 1667–1746), one of the most celebrated physicians of the Qing Dynasty, who is considered the founder of the Warm Disease (Wen Bing) school. His teachings were recorded by his student Gu Jingwen in the seminal text Wen Re Lun (温热论, Discussion of Warm-Heat Diseases), a remarkably concise work of only about 4,000 characters that nevertheless revolutionized how TCM approached febrile diseases.
Before Ye Tianshi, practitioners relied primarily on the Six Stages theory from Zhang Zhongjing's Shang Han Lun (2nd century CE), which was designed for cold-type diseases. However, physicians noticed that many epidemic diseases—particularly in southern China's warmer climate—didn't follow the patterns described for cold damage. Ye Tianshi developed the Four Levels to address this gap, creating a framework specifically suited to heat-type pathogens that enter through the nose and mouth rather than through the body's surface.
His work was later expanded by Wu Jutong (吴鞠通, 1758–1836), whose Wen Bing Tiao Bian (Systematic Differentiation of Warm Diseases, completed around 1798–1813) systematized the Four Levels approach and introduced the complementary Three Burner differentiation system. Together, these texts established Warm Disease theory as one of the four pillars of classical Chinese medicine education.
Comparison
Wei Level
卫分Location: Body surface, skin, Lungs | Depth: Most superficial | Severity: Mild, early stage | Key symptoms: Fever with mild chills, headache, sore throat, cough | Tongue: Slightly red edges, thin white coat | Treatment: Light, cool, dispersing—release exterior, expel heat | Prognosis: Excellent if treated promptly
Qi Level
气分Location: Interior organs (Lung, Stomach, Intestines, Gallbladder) | Depth: First interior level | Severity: Moderate, peak symptoms | Key symptoms: High fever, strong thirst, profuse sweating, irritability | Tongue: Red with yellow coat | Treatment: Clear interior heat, preserve fluids | Prognosis: Good, but requires proper treatment
Ying Level
营分Location: Blood vessels, Heart, Pericardium | Depth: Deep interior | Severity: Serious, yin damage begins | Key symptoms: Nighttime fever worse, restlessness, delirium, faint rash | Tongue: Crimson red, little coating | Treatment: Cool Ying, nourish yin, try to redirect heat outward | Prognosis: Guarded, requires careful management
Xue Level
血分Location: Blood, Heart, Liver, Kidneys | Depth: Deepest | Severity: Critical, life-threatening | Key symptoms: Severe delirium, bleeding (various sites), dark purple rash, possible convulsions | Tongue: Deep crimson or purple | Treatment: Cool blood, stop bleeding, disperse stasis | Prognosis: Serious, risk of complications
Wei Level (Defensive)
卫分证The Wei (卫, meaning 'defense' or 'guard') level represents the body's first line of defense—similar to what Western medicine might call the early immune response. At this stage, the pathogen is still at the body's surface, affecting the Lungs and skin. Symptoms typically include: fever with mild chills, headache, slight thirst, sore throat, cough, thin white tongue coating, and a floating, rapid pulse. Treatment focuses on releasing the exterior and expelling heat—typically using cooling, dispersing formulas like Yin Qiao San or Sang Ju Yin. If treated effectively at this stage, the disease can be resolved before it penetrates deeper.
Qi Level (Interior Heat)
气分证When the pathogen breaks through the Wei level defenses, it enters the Qi (气) level—the first interior stage. Here, the battle between the pathogen and the body's vital energy creates intense internal heat. This level primarily affects the Lungs, Stomach, Intestines, and Gallbladder. Symptoms include: high fever, intense thirst with desire for cold drinks, profuse sweating, irritability, restlessness, red tongue with yellow coating, and a rapid, forceful pulse. Though symptoms are more severe, this stage is generally not life-threatening. Treatment aims to clear heat from the Qi level using formulas like Bai Hu Tang (White Tiger Decoction).
Ying Level (Nutritive)
营分证The Ying (营, 'nutritive') level represents heat penetrating into the blood vessels and beginning to affect the Heart and mind. At this level, both the pathogen and the body's defenses are being damaged—yin fluids are being consumed. Key symptoms include: fever that worsens at night, mental restlessness, insomnia, delirium or confused speech, faint skin rashes, dry mouth without much thirst, deep red (crimson) tongue with little coating, and a thin, rapid pulse. If heat enters the Pericardium (the Heart's protective envelope), severe symptoms like unconsciousness may occur. Treatment focuses on clearing heat from the Ying level and protecting yin fluids, using formulas like Qing Ying Tang.
Xue Level (Blood)
血分证The Xue (血, 'blood') level is the deepest and most critical stage, where heat has fully entered the blood, causing bleeding and severe organ dysfunction. The Heart, Liver, and Kidneys are primarily affected. Symptoms include: severe restlessness or delirium, various forms of bleeding (nosebleeds, vomiting blood, blood in stool or urine), dark purple skin rashes, very deep red or purple tongue, and a fine, rapid pulse. In severe cases, internal wind may arise, causing convulsions, muscle spasms, or stiff neck. Treatment requires cooling the blood, stopping bleeding, and dispersing blood stasis using formulas like Xi Jiao Di Huang Tang.
Practical Application
Tracking Disease Progression: The Four Levels functions as a clinical GPS for febrile diseases. When a patient presents with what appears to be an acute infection, the practitioner assesses which level the disease has reached: Is it still superficial (Wei) with mild symptoms? Has it generated strong internal heat (Qi)? Is it affecting the mind and depleting fluids (Ying)? Or has it reached the critical blood level (Xue)? Each level requires different treatment strategies—using the wrong approach can worsen the condition.
Anticipating Complications: Diseases don't always progress in a neat sequence. Ye Tianshi described 'reverse transmission' (逆传) where disease can skip from Wei level directly into Ying level if the patient has underlying Heart weakness or if the pathogen is particularly virulent. Practitioners watch for warning signs of this dangerous pattern. Similarly, 'combined patterns' can occur—like 'Qi-Ying simultaneous disease' (气营两燔)—requiring formulas that address multiple levels.
Modern Clinical Use: The Four Levels remains actively used in Chinese hospitals today, particularly for viral infections, pneumonia, encephalitis, and epidemic diseases. During the COVID-19 pandemic, treatment protocols in China frequently referenced Four Levels theory to categorize patient presentations and guide herbal prescriptions at different disease stages.
Clinical Relevance
Guiding Treatment Strategy: Each level has specific treatment principles: 'At Wei level, promote sweating to release the exterior; at Qi level, clear heat; entering Ying level, cool the Ying and try to redirect heat outward to Qi; at Blood level, cool the blood and disperse stasis.' These principles prevent the common mistake of using overly cold formulas too early (which can trap the pathogen) or using exterior-releasing formulas when the disease has already gone interior.
Tongue and Pulse Diagnosis: The Four Levels provides clear diagnostic markers. Tongue changes are particularly important: white coating suggests Wei level; yellow coating indicates Qi level; crimson red tongue body indicates Ying level; deep purple tongue indicates Xue level. These visual cues help practitioners quickly assess severity and track treatment progress.
Integration with San Jiao Theory: In clinical practice, Four Levels differentiation is often combined with Three Burner (San Jiao) differentiation—another framework from Warm Disease theory. The Four Levels describes the depth of penetration (surface to deep), while San Jiao describes the location (upper, middle, or lower body). Together, they provide a comprehensive clinical picture for managing complex febrile diseases.
Common Misconceptions
'The Four Levels must always progress in sequence'—While the typical pattern moves from Wei → Qi → Ying → Xue, this is not inevitable. With proper treatment, disease can be resolved at any level. Conversely, severe pathogens or weakened patients may experience 'reverse transmission' where disease skips levels entirely, going directly from Wei to Ying, or may even begin at deeper levels without showing Wei-level symptoms at all.
'The Four Levels replaces Six Stages'—These are complementary systems, not competitors. Six Stages (from Shang Han Lun) is best suited for cold-type invasions, while Four Levels addresses warm-heat diseases. Skilled practitioners use both frameworks depending on the clinical presentation. Some modern teachers emphasize that the underlying principles of tracking disease progression apply to both systems.
'Wei Level means exterior, so use sweating herbs'—While Wei level is at the body's surface, the treatment principle is not identical to the exterior-releasing methods used for cold damage. Since we're dealing with heat pathogens, the approach is 'light, cool, and dispersing'—using acrid-cool herbs rather than the warming diaphoretics used for cold invasion. Ye Tianshi's famous maxim 'At Wei level, promote sweating' must be understood in this context.
Classical Sources
Wen Re Lun (温热论)
Opening Section温邪上受，首先犯肺，逆传心包
Warm pathogens are received from above, first attacking the Lung; reverse transmission reaches the Pericardium
Wen Re Lun (温热论)
Treatment Principles大凡看法，卫之后方言气，营之后方言血。在卫汗之可也，到气才可清气，入营犹可透热转气，入血就恐耗血动血，直须凉血散血
Generally speaking, after Wei comes Qi, after Ying comes Blood. At Wei level, promote sweating; at Qi level, clear the Qi; entering Ying, one may still redirect heat outward to Qi; entering Blood, one must fear consumption and stirring of blood, and should directly cool and disperse the blood
Wen Bing Tiao Bian (温病条辨)
Upper Burner Section太阴温病，不可发汗
In warm disease of Tai Yin (Lung), do not induce sweating [with warming methods]
Modern References
Diagnosis in Chinese Medicine: A Comprehensive Guide
Comprehensive modern textbook with detailed explanation of Four Levels differentiation for Western practitioners
Warm Diseases: A Clinical Guide
Eastland Press clinical guide focusing on practical application of Wen Bing theory
Systematic Differentiation of Warm Diseases (Translation)
Recent authoritative English translation of Wu Jutong's Wen Bing Tiao Bian with extensive annotations
温病学 (Warm Disease Studies)
Standard Chinese university textbook on Wen Bing theory, widely used in TCM education in China