sorry I messed up I copied tongue coating thickness,
Tongue Coating Color Explained
No coating: Yin deficiency.
Yin deficiency is a lack of fluids and/or cooling mechanisms in your body. The tongue coating tells us about the fluids in your digestion specifically, and should there be no coating, we can assume that not only is there a deficiency of fluids in your stomach and intestines but elsewhere as well.
White coating: Normal, or cold dampness.
Cold dampness is like saying the weather is cold and foggy inside your body.
When the white coating is thin, this is normal. A thin white coating is defined as a white coating that is thick enough to see, but thin enough to see through.
When the white coating is thick, this is cold dampness and arrives when either the energy of digestion is deficient or when the diet is especially difficult to digest.
Dirty white or light yellow coating: Cold becoming hot.
Cold becoming hot is to say that what began as a common cold is turning into a flu.
Yellow coating: Internal heat.
Internal heat means that you have a fever, or else metabolic functions are operating in some other state of hyperactivity.
Brown coating: Internal heat that is damaging the Yin or a bismuth based antacid.
Internal heat damaging Yin is what we call it when a high fever or other source of heat causes dehydration.
Bismuth based antacid can give rise to some funny looking stools too. Pepto-Bismol is an example of this kind of product. It does not indicate a pathology, its just a unique reaction to the bismuth in the medicine.