TCM is comprehensive and much information can be gathered from it such as the degree of pathogenic factor and the state of the organs.

Tongue diagnosis is a technique used to diagnose disease or medical conditions.

Tongue coating reflects the state of yang organs. The tongue coating is the layer over the tongue. A normal healthy coating should be white, thin, and allow the tongue body to be seen through the coating. The moisture of the tongue reflects the condition and transport of body fluids. Normal coating is slightly moist. If fluids become deficient the tongue will dry out. Tongue coating color shows the relative heat and cold of the condition and the severity of the pathogen. The thickness of the coating is relative to the amount of the pathogenic factor present. Increasing thickness means the pathogen is going deeper whereas the change from thick to thin reveals an improvement. Examples of different tongue coatings reflecting weak zheng qi include: yellow (heat); watery (yang deficiency); sticky and clear (phlegm damp retention); foul breath (heat); foamy (wind). These are just examples, there are many other patterns.

Different regions of the tongue are related to different parts of the body, internal organs and channels, for example: The tip of the tongue or "upper jiao" is related to the heart and lungs. The sides of the tongue are related to the liver and gallbladder. Middle of the tongue or "middle jiao" is related to the digestion system, stomach and spleen. The back of the tongue or "lower jiao" is related to the kidneys, urinary bladder and intestines.

When a practitioner of TCM looks at a patient’s tongue he/she is looking at many things such as the tongue body, shape, movement, coating as well as the yin and yang organs reflected on the tongue. Tongue diagnosis in TCM is comprehensive and much information can be gathered from it such as the degree of the pathogenic factor and the state of the organs as well as pregnancy issues.