Diagnostic Verse of Tongue Examination in Traditional Chinese Medicine
The tongue and its coating must first be distinguished; the coating is the fur, the tongue itself is the substance. The coating examines qi disorders, the tongue body examines blood diseases; yin-yang, exterior-interior, cold-heat, and deficiency-excess. The depth of pathogenic factors can be known by observing the coating; the excess or deficiency of the organs can be identified by the tongue body.
Changes in the tongue coating have different distributions: the tip corresponds to the heart and lungs, the center to the stomach, the root to the kidneys, the sides to the spleen, and the areas on both sides of the tongue correspond to the liver and gallbladder. Another method divides it into three parts: the upper, middle, and lower jiao (burners), with the tip corresponding to the upper, the root to the lower, and the center of the tongue to the middle jiao.
Differentiating the tongue's moisture, it can be moist, dry, slippery, or rough. Moistness mostly indicates normalcy, while a thick coating indicates dampness. A moist and overly wet tongue indicates a slippery coating. Roughness is associated with dryness, and extreme dryness signifies exhaustion of fluids.
Whether the tongue has "spirit" (shen) is determined by its luster or withered appearance. "Lustrous" means moist and vibrant, with fluids well-distributed; it is reddish, moist, and bright, indicating abundant qi and blood. "Withered" means a lack of color, as vital qi is about to be exhausted; lacking fluids and being dry indicates a critical illness.
A red tongue primarily indicates heat, but there are many distinctions. Flaming heart fire manifests as a red tip. Redness on the sides of the tongue indicates heat in the liver and gallbladder. In the early stage of warm diseases, the tip and sides are often red. In miscellaneous diseases, it indicates the color of the heart and liver, often accompanied by headache, insomnia, irritability, and constipation.
A bright red tongue also has different causes: in warm diseases, it indicates severe heat; in miscellaneous diseases, it indicates yin deficiency. A dry, red center of the tongue signifies that yin fluids have been damaged. A smooth, tender, and dry tongue is a "mirror tongue," indicating a poor prognosis with exhausted fluids. If it is due to qi and blood deficiency, the tongue body will be pale red.
A deep red (crimson) tongue indicates that warm-heat has transmitted to the nutritive level. A pure, fresh, and glossy crimson tongue indicates intense heat in the pericardium. A withered and dry crimson tongue signifies exhaustion of kidney yin; often accompanied by a dry throat, it indicates a fatal condition. Another type is a crimson tongue with little or no coating, even with cracks, indicating that yin fluids are about to be depleted.
A sticky, greasy crimson tongue, resembling a coating but not truly one, indicates dampness mixed with turbidity, which should be resolved with aromatic, pungent herbs that open the orifices. It may look dry but feels moist to the touch; this signifies damaged fluids due to damp-heat steaming upward, with turbid phlegm clouding the orifices, requiring treatment to clear heat and promote fluid production.
A purple tongue indicates disease, which can be of yang or yin nature; the presence or absence of coating is the main differentiator. Moisture, dryness, depth of color, and whether it covers the whole tongue or appears in patches indicate different diseases and varying severity. A yellow coating on a purple tongue indicates accumulated heat in the organs; if accompanied by dryness, urgent purgation is necessary.
A blue-purple tongue with a floating, slippery, and moist coating indicates the early stage of cold damage, directly affecting the three yin organs. In diseases of blood stasis, the tongue is purple and dull, generally slippery and moist, or may have a gray coating; severe cases show it over the whole tongue, while mild cases show patches. This is similar to conditions where prolonged pain enters the collaterals.
In alcoholics with accumulation, the tongue often has purple patches. A white, slippery center indicates damage from cold after drinking. A swollen and purple tongue indicates alcohol poisoning, which is dangerously close to affecting the heart and difficult to save.
Changes in blue color are similar to a purple tongue; it can still produce a coating, indicating vital qi is not yet exhausted. A blue, glossy, uncoated tongue that is dull and lacking luster indicates an extremely dangerous condition with exhausted primordial qi. When blue does not cover the whole tongue, it indicates different syndromes: in epidemic diseases with foul turbidity, it may be accompanied by a white, powdery coating; a yellow, greasy, turbid coating indicates damp-warmth with depressed heat; a slippery coating with a blue center indicates a damp-phlegm tongue.
Black coating indicates severe disease, which can be of yin or yang nature: a tender, slippery, and moist coating indicates extreme cold; a rough, dry, and scorched coating is caused by extreme heat. It signifies that blood is already damaged, which ancient texts called a fatal sign; if identified early and treated promptly, there might still be a chance of recovery.
Whether the tongue is "old and coarse" or "tender and delicate" also needs analysis: a firm, contracted, old, and coarse tongue indicates excess heat accumulation, and if the spirit is still present, the disease is mostly excess. A swollen, puffy tongue indicates deficiency-cold or phlegm-dampness. A tender tongue with tooth marks indicates deficiency.
Cracks, peeled areas, and prickles each have their own signs: cracks on the tongue body resemble broken porcelain, seen in blood deficiency, intense heat, or also yin deficiency. Peeling resembles a patch of smooth, clean surface, a sign of yin damage that is often difficult to fill. In more severe cases, the entire tongue may be peeled.
Prickles on the tongue can be black or yellow, appearing anywhere, indicating a tendency towards dryness. A swollen tongue body indicates phlegm-fluid, heat, and dampness. A shrunken and withered tongue body indicates various acute deficiency syndromes.
A soft and flexible tongue is normal, with flexible movement indicating harmony between qi and blood. A flaccid, crimson tongue indicates yin deficiency with weak movement; if the color is pale red, it indicates extreme deficiency of qi and blood. A stiff tongue body can be differentiated as wind, fire, or phlegm: a stiff, paralyzed tongue indicates wind invading the heart and spleen; a red, swollen, and stiff tongue indicates extreme heart fire; a swollen and stiff tongue with a turbid, gray coating indicates phlegm.
The extension and retraction of the tongue are normally easy for a healthy person. If extension is weak, trembling indicates deficiency. If the tongue feels as if it is being pulled by a thread when trying to extend, there are three possible causes: dryness, extreme cold, or phlegm-fluid, all of which affect the muscles and tendons, leading to a stiff tongue and difficult speech. Dryness and extreme cold, or wind-phlegm adhesion, cause a stiff tongue when extended. Heat-phlegm causes a stiff tongue upon extension, while numbness indicates deficiency. Deviation to one side indicates wind striking the collaterals. Protrusion, licking, or smacking the lips indicates heat accumulation in the heart and spleen, often seen in infantile convulsions.
A suddenly retracted tongue that is dry and red indicates damage to yin; a white, moist, retracted tongue indicates cold凝结 (coagulation); a sticky, greasy, and curled tongue indicates fatigue and dampness.
Whether the coating is "rooted" or "rootless" must also be distinguished, as it relates to the existence of the middle qi. A rooted coating grows from the tongue, closely adhering to its surface and spreading evenly. A rootless coating is a thick patch that is clean around the edges, like something applied to the surface.
A thick or thin coating indicates the binding of external or internal pathogens. External cold damage usually has a thin coating, with accompanying syndromes varying; pathogenic accumulation results in a thick coating, often indicating an internal excess condition. A rotten coating is loose and thick, which can be wiped away; it signifies that healthy qi is transforming pathogens, and there is an excess of yang qi. A greasy coating sticks to the tongue and cannot be scraped off; it indicates phlegm-dampness residing in the middle jiao, where yang is blocked by yin. A rotten coating that looks like mold or rotten pus indicates a failure of stomach qi, or possibly an internal abscess.
A coating covering the whole tongue indicates that pathogenic factors are widespread; in an external syndrome, it is a thin white coating, while a white, greasy coating indicates phlegm. Medication should be used with caution to prevent changes in the condition. A coating appearing only on one part of the tongue—back, front, left, or right—should be studied according to its corresponding area. Changes in coating color can indicate favorable or unfavorable progression: changing from white to yellow, then yellow receding and new coating appearing is a favorable sign, indicating pathogenic factors are resolving and healthy qi is prevailing. Progressing from white to yellow to gray to black indicates that healthy qi cannot support itself and the pathogenic factors are deepening. If the coating suddenly disappears without gradual transformation, it indicates that pathogenic factors have penetrated internally, a dangerous condition.
Be aware of food staining the coating. Loquats and olives can turn the coating yellow or black. Sweet, sour, salty foods, as well as colored drinks and juices, can all stain the coating, often resulting in a white, moist tongue.
A white coating primarily indicates exterior syndromes, as well as dampness, deficiency, and cold. A white, slippery coating indicates external wind-cold. A white coating on a red tongue indicates the initial stage of wind-warmth. A white coating turning yellow indicates that pathogenic factors have transmitted internally. A white coating on a crimson base indicates dampness suppressing heat. A white, sticky coating indicates internal binding of phlegm-dampness.
A white, moist coating with red impressions on the tip and sides, accompanied by a swollen tongue, indicates a damp-phlegm syndrome. In deficiency syndromes, the white coating looks clear and bright, and the tongue is often tender and slippery, indicating a yang deficiency syndrome.
A yellow coating primarily indicates internal diseases and heat. A slightly yellow, non-dry coating needs differentiation in the early stage of transmission; a yellow, dry coating indicates extreme internal heat. A yellow coating concentrated in the center indicates excess syndrome of the Yangming fu organs. Dryness giving rise to black prickles or cracks indicates deep heat with depleted yin fluids.
A yellow, slippery, and greasy coating indicates binding of phlegm, dampness, and heat. The above yellow coatings all belong to heat-excess syndromes. Another type is a pale, loose, flower-like color—yellow and pale, on a swollen, tender tongue body, with moist and cool fluids, indicating spleen deficiency with dampness.
A gray coating indicates disease related to cold, heat, yin, or yang; differentiation depends on moisture or dryness and requires careful observation. A gray coating that develops from yellow, being dry, thick, and scorched, indicates the transmission of cold damage through the meridians, an internal heat syndrome. A gray coating that suddenly appears without accumulation, being thin and slippery, indicates a three-yin syndrome.
A gray, slightly black, slippery coating on a moist tongue body indicates phlegm-fluid or edema, which can be identified through careful differentiation.
Black and gray coatings are similar in diagnosis. A gradual progression from gray to black indicates deepening internal heat. A black, dry, and cracked tongue indicates heat damage with fluid depletion. A dry black coating at the root indicates severe heat in the lower jiao. Both indicate excess heat, requiring urgent purgation to preserve yin. A black, slippery, and moist coating indicates direct penetration of yin-cold; in miscellaneous diseases, it is also associated with yang deficiency. Some people, due to their constitutive phlegm-fluid, normally have a gray-black, slippery tongue without a dangerous condition, so there is no need for alarm.
The constitution of a healthy person can have different tongue coatings. Commonly, there may be a thick coating, gray-yellow or white, indicating disease in the spleen and stomach related to damp-heat. When illness occurs, the coating may instead become thin or peel off, indicating insufficiency of the middle qi, which requires careful identification. A red tongue without coating, with red dots on the tip and sides, seen in a healthy person, verifies yin deficiency.
Moisture, dryness, thickness, and thinness can reveal the pathogen and healthy qi; observing the tongue is the key to syndrome differentiation, the guiding principle. Moisture indicates the presence of fluids, while dryness indicates heat invasion; thickness indicates disease progression, while thinness indicates mild pathogenic factors. Combined with the color of the coating, the condition becomes clear. If caused by food or drink, this must be discerned to avoid confusion.
Examine the tongue before eating to distinguish thickness; examine before drinking to distinguish moisture. Remember the information above about tongue coatings; apply it skillfully and without confusion in clinical practice.