Tongue observation is a key and reliable element of TCM diagnosis. It is, together with pulse diagnosis, one of the two most important diagnostic methods.

We examine it to determine:

• The predominance and weakness of vital energy and pathogenic energy.
• Whether there is a Full or Empty pattern.
• The location of the disease (superficial or deep, and according to the tongue zone, which organs are affected).
• The nature of the disease (Heat or Cold pattern).
• The prognosis of the disease.

Tongue diagnosis in traditional Chinese medicine

To perform a correct tongue observation, it is advisable to use natural light, although this is not always possible. The patient should extend the tongue without forcing it; the tongue should be flat with the tip pointing slightly downward.

When inspecting the tongue, we examine it quickly from tip to root. If we do not want to miss any detail, we can follow these four steps:

• 1- The colour of the tongue body, which may be pale, red or purple
• 2- The shape of the tongue: whether it is long or short, thick or thin, and whether it has cracks or swellings
• 3- The tongue coating: its colour, thickness and moisture
• 4- The Lustre or Shen of the tongue.

The tongue should not be kept outside the mouth for too long because it dries out and the colour, shape and texture may change. It is better for the patient to extend the tongue several times if we need to continue observing it.

Consult in summary form the quick guide to tongue and coating diagnosis

Tongue zones

The different zones of the tongue correspond to the Zang Fu organs and bowels. Alterations in any of these zones, such as changes in colour, shape, cracks, swellings or changes in the coating, help us in the diagnosis of disease.

Other tongue maps exist that vary slightly in their details. In general terms they agree:

• The root of the tongue is related to the Lower Burner and reflects the Kidney, Bladder, Large Intestine and Small Intestine. A thicker and yellower coating at the root may reflect accumulation of food in the intestines or Damp-Heat in the Bladder.
• The central zone of the tongue is related to the Middle Burner. In the centre it reflects the state of the Stomach, Spleen and on the sides Liver and Gall Bladder. Redder tongue edges may indicate rising of Liver-Yang. Absence of coating in the centre of the tongue and cracks may indicate Stomach-Yin Deficiency.
• The tongue tip is related to the Upper Burner. The tip reflects the Heart and the area surrounding it reflects the lungs. For this reason, states of nervousness and anxiety often present with a red tongue tip. Some chronic lung pathologies present with cracks or swellings in the lung zone.

To make a good diagnosis, it is important not to become fixated on a single detail observed on the tongue. Try to view it as a whole and see whether our perception corresponds with the patient's symptoms and pulse.

The healthy tongue

As a reference, a normal tongue has the following characteristics:

• Colour: pinkish and with a fresh appearance.
• Lustre: shiny and lively.
• Shape: flexible and without cracks or ulcers; the tongue has a proportionate size and thickness.
• It does not tremble when extended.
• The coating is smooth, whitish and slightly thicker at the root (because the Lower Burner is always somewhat more turbid).
• The coating should be moist.

Normal variations in the tongue

It should be considered that the tongue will vary according to several factors. For example:

• The older the person, the more deteriorated the tongue is; it has more cracks and is rougher.
• The size of the tongue should be proportionate to the person's constitution: a person with obesity will have a broader face, a larger mouth, and a larger and thicker tongue.
• Some products such as coffee, tobacco, squid ink, turmeric or liquorice change the colour of the tongue.
• Hot drinks cause the tongue to become redder.
• If the person breathes through their mouth, their tongue is drier.
• Depending on the time of day there are also changes: in the morning the tongue tends to be dirtier, while after eating the coating tends to be thinner.
• The tongue can also change according to the season: in summer the coating is thicker and more yellowish, in autumn the coating is smoother and drier, and in winter the coating is slightly more moist.