We can think of the 8 Principles when observing the tongue.

• The tongue body tells us the state of Yin and Yang, deficiency and excess. It also indicates the state of the Zang organs.
• The coating reflects the state of Cold and Heat. And it indicates the state of the Fu organs.

Pale Tongue

• Pale or pinkish with transparent coating: Deficiency and Cold in Spleen and Stomach.
• Pale with thick coating: Blood deficiency and Qi deficiency. Exhaustion of Yang.
• Pale with dry coating: Stagnant Heat injuring the Body Fluids.
• Pale with yellow coating: Deficiency of the Middle Burner. Cold or Dampness.
• Pale with black coating: Yang deficiency and excess of Cold.

Red Tongue

• Red with thin white coating: Yin deficiency injured by external pathogenic factors.
• Red with white and slippery coating: Yang deficiency and excess of Dampness.
• Red with white and dry coating: Dryness and Heat injuring the Body Fluids.
• Red with white coating and red spots: External pathogenic factors have not been eliminated. Toxic Heat.
• Red with yellow and moist coating: Yin deficiency with Dampness.
• Red with yellow and sticky coating: Excess Heat in the Stomach.
• Red with yellow and dry coating: Very severe Heat patterns.

Purple Tongue

• Purple with white and sticky coating: Wind-Cold invading the body. Injuries from alcoholism.
• Purple with yellow and slippery coating: Stagnation of Cold in the vessels or stagnation of food in the stomach.
• Purple with yellow and dry coating: Excess Heat in the stomach and intestines.