Small Intestine
The Small Intestine is a Fu (Yang) organ belonging to the Fire element that receives food from the Stomach and separates usable nutrients ("pure") from waste ("impure"). Paired with the Heart, it influences both digestion and mental clarity.
Five Element Correspondences
Season
Summer
Climate
Heat (Shu)
Emotion
Joy (via Heart connection)
Color
Red
Taste
Bitter
Sound
Laughing (via Heart connection)
Direction
South
Sense Organ
Ear (via meridian connection)
Body Tissue
Blood vessels (via Heart connection)
Body Fluid
Ye (Thick Fluids) - "Small Intestine governs fluids"
Peak Hours
13-15
Meridian
Small Intestine Meridian
Educational content · Consult qualified TCM practitioners for diagnosis and treatment
Overview
In Traditional Chinese Medicine (TCM), the Small Intestine (Xiǎo Cháng) is one of the Six Fu (hollow Yang) organs responsible for processing and transforming food and fluids. Unlike the Western anatomical view that focuses purely on digestion, TCM views the Small Intestine as having both physical and mental-emotional functions.
The Small Intestine receives partially digested food from the Stomach and performs its signature function: separating the "pure" (usable nutrients and fluids) from the "impure" (waste). This fundamental role earned it the classical title of "Separator of the Pure from the Impure" and "Transformer of Qi." The pure essences are sent upward to the Spleen for distribution throughout the body, while waste products are directed downward—solid waste to the Large Intestine and excess fluids to the Bladder.
Through its interior-exterior pairing with the Heart, the Small Intestine's separating function extends beyond the physical realm to influence mental clarity and decision-making. Just as it sorts nutrients from waste in digestion, it helps sort useful thoughts from useless ones, supporting the Heart's role in clear thinking and judgment.
Historical Context
The Small Intestine has been recognized as one of the Six Fu organs since the earliest Chinese medical texts. The Huangdi Neijing (Yellow Emperor's Classic, compiled around 475-221 BCE) established its fundamental role, describing it as "the Official of Reception from which the transformation of matter emerges." This classical text documented both its anatomical position—between the Stomach and Large Intestine—and its key physiological functions.
During the Ming Dynasty, physician Li Zhongzi in his work "Neijing Zhiyao" (Essentials of the Inner Classic) further elaborated the concept of "separating the clear from the turbid" (泌别清浊), which became central to understanding Small Intestine function. Zhang Jiebin's "Lei Jing" (Classified Classic) provided detailed commentary on how the Small Intestine works with the Spleen's ascending function and coordinates fluid metabolism with the Bladder.
Historically, Small Intestine pathology was often treated through its paired organ, the Heart, or attributed to Spleen dysfunction. The clinical pattern "Heart Fire Transferring to Small Intestine" became an important diagnostic category, explaining the connection between emotional disturbance and urinary symptoms like painful or bloody urination.
Physiological Functions
Receiving and Containing
受盛化物 (Shòu Chéng Huà Wù)The Small Intestine receives partially digested food (chyme) from the Stomach through the pylorus (You Men) and holds it for further processing. This "receiving" function makes it a vessel or container where transformation occurs. The classical texts describe the Small Intestine as the "Official of Reception" emphasizing this crucial holding and processing role in digestion.
Separating Pure from Impure
泌别清浊 (Mì Bié Qīng Zhuó)The Small Intestine's most distinctive function is sorting usable nutrients ("clear") from waste ("turbid"). The pure essences and fluids are absorbed and sent to the Spleen for distribution throughout the body. The impure solid waste passes through the Valve Gate (Lan Men) to the Large Intestine, while excess fluids are directed to the Bladder for urination. This function directly influences both bowel and urinary function.
Governing Fluids
小肠主液 (Xiǎo Cháng Zhǔ Yè)The Small Intestine plays a significant role in fluid metabolism by controlling how much water is absorbed versus excreted. Because it determines whether fluids go to the Bladder or Large Intestine, it directly affects urination and stool consistency. This is why TCM uses the principle "benefit urination to firm the stool" (利小便以实大便) when treating diarrhea.
Mental Discernment
分清别浊于心神 (Fēn Qīng Bié Zhuó Yú Xīn Shén)Through its relationship with the Heart, the Small Intestine extends its sorting function to the mental level. Just as it separates useful nutrients from waste physically, it helps the mind distinguish useful thoughts from useless ones, supporting clear judgment and decision-making. When this function is impaired, mental confusion, poor judgment, or difficulty making decisions may occur.
Relationships with Other Organs
Other
The Heart and Small Intestine form an interior-exterior (Biao-Li) pair through their meridian connections. The Heart meridian descends through the diaphragm to connect with the Small Intestine, while the Small Intestine meridian ascends to connect with the Heart. Heart Fire can transfer downward to the Small Intestine, causing urinary symptoms like painful, dark, or bloody urination along with mouth ulcers and mental restlessness. This pairing also extends to mental function—the Small Intestine supports the Heart's clarity of mind through its sorting function.
Other
The Stomach sends partially digested food (chyme) downward to the Small Intestine through the pylorus (You Men). The Small Intestine depends on the Stomach's descending function to receive food for further processing. Both organs share the principle that Fu organs must remain unobstructed to function properly ("Fu organs function well if they are unobstructed").
Other
The Spleen's transforming and transporting function works closely with Small Intestine digestion. After the Small Intestine separates the pure essences, it relies on the Spleen's ascending function to distribute these nutrients throughout the body. Clinically, Small Intestine weakness often manifests as Spleen patterns, and digestive problems are frequently treated through the Spleen rather than the Small Intestine directly.
Other
The Small Intestine directs excess "turbid" fluids to the Bladder for excretion as urine. This direct functional relationship means that Small Intestine dysfunction often affects urination—excess heat causes scanty, dark, burning urine, while deficient cold leads to frequent, clear urination. The principle of "benefit urination to firm the stool" utilizes this relationship in treating diarrhea.
Other
The Small Intestine sends solid waste through the Valve Gate (Lan Men) to the Large Intestine for final processing and elimination. The Large Intestine further absorbs fluids and forms stool. If the Small Intestine fails to properly separate fluids, excessive water enters the Large Intestine, causing loose stools or diarrhea.
Common Pathological Patterns
Key Manifestations
Key Manifestations
Key Manifestations
Key Manifestations
Tongue Manifestations
The tongue provides diagnostic clues about Small Intestine conditions. Since the Small Intestine is paired with the Heart, the tongue tip (which corresponds to the Heart) is particularly significant. A red tongue tip with or without sores suggests Heart Fire, which may transfer to the Small Intestine. Mouth ulcers, especially on the tongue, often indicate Heat in both Heart and Small Intestine.
For Small Intestine Excess Heat patterns, look for a red tongue body with red tip, possible ulcers, and a yellow coating. For Deficient Cold patterns, expect a pale tongue with a white, moist coating. Damp-Heat in the Small Intestine typically presents with a red tongue and yellow, greasy coating.
Pulse Manifestations
The Small Intestine does not have a dedicated pulse position in traditional pulse diagnosis. However, because it pairs with the Heart, pathological changes often reflect at the left cun (inch) position where the Heart pulse is assessed.
For Small Intestine Excess Heat (especially Heart Fire transferring down), expect a rapid (Shu) pulse, often surging or overflowing (Hong) at the cun position. For Small Intestine Deficient Cold, the pulse will be deep (Chen), slow (Chi), and weak (Ruo). Small Intestine Qi Stagnation typically presents with a wiry (Xian) or tight (Jin) pulse.
Clinical Relevance
In clinical practice, Small Intestine patterns often overlap with Spleen, Stomach, and Bladder conditions. The most commonly encountered pattern is Heart Fire Transferring to Small Intestine, which presents with both emotional symptoms (restlessness, insomnia) and urinary symptoms (dark, scanty, burning urine). This pattern is treated by clearing Heart Fire and promoting urination using formulas like Dao Chi San.
The Small Intestine's role in fluid separation has important therapeutic applications. The principle "benefit urination to firm the stool" (利小便以实大便) is based on Small Intestine physiology—by directing more fluid to the Bladder through diuretic herbs, less water enters the Large Intestine, helping to resolve diarrhea. This approach is particularly useful in early-stage diarrhea.
The Small Intestine meridian is clinically valuable for treating pain along its pathway, including neck pain, shoulder blade pain (especially SI-11 area), and ear problems. SI-3 (Houxi) is especially important as the confluent point of the Governing Vessel, used for back pain, stiff neck, and occipital headaches.
Classical Sources
Huangdi Neijing Suwen
Chapter 8 - Linglan Midian Lun小肠者，受盛之官，化物出焉
The Small Intestine is the Official of Reception; the transformation of matter comes from it
Yixue Rumen (Introduction to Medicine)
Zangfu Chapter小肠上接胃口，受盛其糟粕传化，下达膀胱，泌别其清浊宣通
The Small Intestine connects above to the stomach opening, receives and transforms the food residue, reaches down to the Bladder, and separates the clear from the turbid for proper circulation
Lei Jing (Classified Classic)
Zangxiang Lei (Visceral Manifestations)小肠居胃之下，受盛胃中水谷而分清浊
The Small Intestine resides below the Stomach, receives water and grain from the Stomach, and separates the clear from the turbid
Modern References
The Foundations of Chinese Medicine
Comprehensive modern textbook detailing Small Intestine physiology, pathology, and clinical patterns
Chinese Acupuncture and Moxibustion
Standard reference for Small Intestine meridian points and clinical applications
The Yellow Emperor's Classic of Medicine
Accessible modern translation of Huangdi Neijing with commentary on Zang-Fu theory