Tongue diagnosis in TCM: what a practitioner looks at

In Traditional Chinese Medicine (TCM), the tongue is one of the few parts of the inside of the body you can see directly. Practitioners have looked at it for centuries, alongside questions about how you feel, your pulse and your face. This guide explains what they look at and what the tradition reads in it.

Why TCM looks at the tongue

Tongue diagnosis [舌诊] is part of what TCM calls the four examinations: looking, listening and smelling, asking, and feeling the pulse. The tongue belongs to looking, and for many practitioners it is the most informative part of it.

In TCM theory, the tongue reflects the state of qi, blood and body fluids, and different areas of the tongue are linked to different organs. Because a tongue can change within days, practitioners compare it from one visit to the next rather than judging a single look.

What TCM considers a balanced tongue

The classical description of a balanced tongue is a pale red body with a thin white coating. It is moist without being wet, has no deep cracks, is neither swollen nor thin, and moves freely. Everything else a practitioner notes is a difference from this picture.

The colour of the tongue body

Practitioners first look at the colour of the tongue itself, underneath any coating. The tradition links each colour to a different picture:

Pale. Paler than pale red. TCM associates it with patterns such as Qi Deficiency [气虚] and Blood Deficiency [血虚], or with cold.
Red. Redder than normal, read as a sign of heat. A red tongue with little or no coating is the classic picture of Yin Deficiency [阴虚].
Deep red. A dark, crimson red, which the tradition reads as stronger or longer standing heat.
Purple or bluish. Linked in TCM with qi or blood that does not flow freely.

Shape and other features

The shape of the tongue and its details add to the picture:

Swollen, with teeth marks along the edges. Often linked with Spleen Qi Deficiency [脾气虚] and with what TCM calls dampness.
Thin. Associated with a shortage of blood or yin.
Cracks. Read according to where they sit and how deep they are. A crack down the middle is linked to the Stomach.
Red dots or a red tip. Associated with heat, at the tip with the Heart.

The coating

The coating is the thin layer on top of the tongue. TCM says a thin, white coating comes from the qi of the Stomach and counts as normal. Practitioners look at its thickness, colour, moisture and where it is missing:

Thick. Linked with dampness or with food that is not being digested well.
Yellow. Read as heat. A white coating is linked with cold or with a normal state.
Peeled or missing in patches. Associated with Stomach Yin Deficiency [胃阴虚] or a shortage of yin in general.
Very wet or very dry. Read as a sign of how body fluids are distributed.

The tongue map

TCM divides the tongue into areas that each reflect an organ system. The tip relates to the Heart and Lungs, the sides to the Liver and Gallbladder, the centre to the Spleen and Stomach, and the back to the Kidneys, Bladder and Intestines.

These organs are functional systems in TCM, not the anatomical organs a doctor examines. A note about the Liver area says nothing about the results of a liver test.

The underside of the tongue

Many practitioners also ask you to lift your tongue, to see the two veins underneath it. In TCM, veins that look dark, swollen or branched are associated with blood that does not flow freely. That is why Noonla asks for a photo of the underside as well as the top.

How to look at your own tongue

A tongue is easy to misread, so it helps to look at it under the same conditions each time:

Look in daylight, or in neutral white light, facing a window.
Look in the morning before you eat, drink coffee or brush your tongue.
Avoid coloured food and drinks beforehand, such as coffee, tea, beetroot, berries and sweets.
Stick your tongue out relaxed and flat, and for no more than about fifteen seconds, since straining changes its colour.
Compare several days rather than drawing conclusions from one look.

A traditional reading, not a diagnosis

A tongue reading describes what TCM observes and what the tradition calls it. It is not a medical diagnosis. See your doctor or dentist if your tongue hurts, if it changes suddenly, or if a sore, lump or white or red patch does not go away within two weeks.