Why do acupuncturists look at your tongue?

Tongue can give important clues to an acupuncturist about the imbalances in your body. In complicated
conditions with many different symptoms, tongue diagnosis nearly always reflects the basic and
underlying pattern.
What we look at is the toungue body color, the shape, the coating and the mositure.  For example,  is your tongue too red or too pale? Or is it pruplish? Is it thin or swollen, too dry or too wet? Is the tongue coating thick or thin, or there is no coating? Is there a crack along the midline? 
After we are done observing your tongue, we can decide if there is too much Heat or  Cold in your body, or if there is Blood, Yin, Qi or Yang deficiency that is causing imbalances in your body/mind. We always make diagnosis using Traditional Chinese Medicine (TCM) terminology, and then plan the treatment accordingly. We don't do medical diagnosis. But, some changes in the tongue appearance may point to certain medical conditions such as diabetis, dysfanction in digestions, thyroid problems, anemia.

It is important to stress that diagnosis is never made on the tongue alone. Complete diagnosis has to take into
account other signs and symptoms that an acupuncturist reviews during the initial appointment with the
patient. So, if you have concerns regarding your tongue appearance, and especially if you also experience
some health problems, make an appointment with an acupuncturist for diagnosis and treatment.