Inspection of tongue, an important part of inspection diagnosis in TCM, is a diagnostic method by means of observing the changes of the body and fur of the tongue.

The tongue is closely related to the viscera and meridians. The tongue is the external part of the heart and is connected with the heart meridian. The tongue also manifests the conditions of the spleen because it is connected with the spleen meridian. The kidney stores essence and the kidney meridian reach both sides of the tongue. The liver stores blood and governs tendons, the liver meridian also extends to the tongue. The lung reaches the throat and is connected with the tongue. The tongue fur is produced by gastric qi fumigating cereal nutrients.

The tongue depends on qi and blood to nourish and body fluid to moisten. So the form, texture and color of the tongue are closely related to the state and circulation of qi and blood. The moisture and dryness of the tongue coating and body are related to the quantity and distribution of body fluid. That is why the tongue can reveal the states of the viscera, qi, blood, yin, yang, pathogenic factors and healthy qi as well as the progress of diseases. So examination of the tongue can enable one to understand internal pathological changes.

The conditions of the tongue among healthy people are the normal states of the tongue marked by suitable size, softness, flexibility, light-red color, luster and moisture; even and whitish thin fur which is neither dry nor greasy and slippery, closely attached to the surface of the tongue, distributed more on the center and root and less on the margins and tip. The normal conditions of the tongue is usually described as "light-reddish tongue with thin and whitish fur", suggesting normal functions of the viscera, sufficiency of qi, blood and body fluid as well as superabundance of gastric qi.