Unhealthy tongue

In Chinese medicine, the state of the tongue is often the clearest indication of a state of disharmony, reliable even when other signs are contradictory. A normal tongue is pale red and moist, and the tongue moss (or coating) is thin and even, whitish and the tongue material can be seen through it. Any variation on this is indicative of imbalance in the body in the following ways:

Tongue colour
Paleness denotes deficient blood or deficient qi or excess cold; red (redder than normal) denotes excess heat; scarlet denotes extreme heat; purple denotes a pattern of stagnant qi or congealed blood (pale purple and/or moist points to cold as the cause of obstruction; reddish purple and/or dry as a heat-related injury to fluids) or to liver disharmony. Moss thick denotes excess; thin during illness denotes deficiency; wet denotes excess fluids or deficient yang or fire; dry denotes deficient fluids or excess yang or fire; "floating", poorly connected moss denotes weak spleen and stomach qi; greasy denotes mucous or dampness (pasty is even more extreme); bare patches denote deficient yin or fluids, or weak spleen qi; white resembling cottage cheese denotes heat in the stomach; yellow denotes heat; black or gray denotes either extreme heat (against a red tongue) or extreme cold (against a pale tongue).

Tongue shape and movement
Puffy with scalloped edges denotes deficient qi or excess fluids (or excess heat when the tongue is very red); thin denotes deficient blood or fluids; stiff denotes wind pernicious influence or mucous obstructing the heart qi; trembling denotes deficient qi when pale and internal wind when red; lolling denotes heat; contracted (unable to extend) serious conditions of cold (pale or purple), mucous or dampness (swollen) or heat injury to fluids (red); cracks in a red tongue denote heat injury to fluids or deficient yin; cracks in a pale tongue denote deficient blood and qi; red eruptions, pimples and protrusions denote heat or congealed blood. Localized signs on different portions of the tongue correspond to certain organs thus: tip - lungs; extreme tip - heart; sides - liver and gall bladder; root - kidney; centre - stomach and spleen.