The Body's Mirror
The tongue is one of the most reliable and accessible diagnostic tools in TCM. Unlike pulse diagnosis, which requires years of training to master, tongue diagnosis can be learned relatively quickly and provides immediate, objective information about the state of the internal organs.
How to Examine the Tongue
For accurate tongue diagnosis: - Examine in natural daylight when possible - Ask the patient to extend the tongue naturally, without straining - Observe for no more than 15-20 seconds (prolonged extension changes the tongue's appearance) - Note the tongue body (color, shape, moisture) and the tongue coating separately
The Tongue Body
Color
Pale: Indicates Blood deficiency or Yang deficiency. The tongue lacks the normal pink-red color because there is insufficient Blood to fill the tongue's vessels, or insufficient Yang to warm and circulate the Blood.
Red: Indicates heat — either excess heat (full heat) or deficiency heat (Yin deficiency with empty heat). The distinction is made by the coating: excess heat produces a thick yellow coating; Yin deficiency produces little or no coating.
Dark Red (Crimson): Indicates severe heat, often in the nutritive or blood level. Seen in febrile diseases and severe Yin deficiency.
Purple: Indicates Blood stasis. The tongue has a bluish-purple hue because Blood is not circulating freely. Can also indicate cold obstructing circulation (pale purple) or heat causing Blood stasis (dark purple).
Blue: Indicates severe cold or Blood stasis with cold.
Shape
Thin: Indicates Blood or Yin deficiency — the tongue lacks the nourishment to maintain its normal size.
Swollen/Puffy: Indicates dampness or phlegm. The tongue is enlarged because fluids are accumulating in the tissues.
Stiff: Indicates internal wind, heat in the Heart, or phlegm misting the mind.
Flaccid: Indicates severe Qi and Blood deficiency or Yin deficiency.
Cracked: Indicates Yin deficiency (if the tongue is red and dry) or Spleen deficiency (if the tongue is pale and wet). Cracks along the midline indicate Stomach Yin deficiency.
Teeth marks: Scalloped edges indicate Spleen Qi deficiency — the tongue is swollen and pressing against the teeth.
Deviated: Indicates internal wind, often associated with stroke or pre-stroke conditions.
The Tongue Coating
The tongue coating (fur) is produced by the Stomach and reflects the state of the digestive system and the presence of pathogenic factors.
Color of Coating
White: Normal or indicates cold or wind-cold invasion. A thin white coating is normal. A thick white coating indicates cold-dampness or food stagnation.
Yellow: Indicates heat. The thicker and darker the yellow, the more severe the heat.
Grey or Black: Indicates extreme heat or extreme cold, depending on whether the tongue body is red (heat) or pale (cold).
Thickness of Coating
Thin: Normal or indicates an early-stage or mild condition.
Thick: Indicates a more severe condition, often with dampness, phlegm, or food stagnation.
Moisture of Coating
Moist: Normal.
Wet/Slippery: Indicates dampness or phlegm.
Dry: Indicates heat consuming fluids or Yin deficiency.
Peeled (no coating): Indicates Stomach Yin deficiency. A completely peeled tongue (mirror tongue) indicates severe Yin deficiency.
Tongue Mapping by Organ
Different areas of the tongue correspond to different organ systems: - Tip: Heart and Lung - Sides: Liver and Gallbladder - Center: Spleen and Stomach - Root: Kidney
Localized changes in color, coating, or shape in these areas provide specific information about the corresponding organ systems.