One of the surprising and exotic things about Chinese Medicine is the practice of looking at the patient’s tongue in order to get general information about the body’s overall condition. I usually explain each patient’s tongue to them, time permitting, but since I refer to it so often on my website, I think it’s about time that I got around to explaining what it is in a bit more detail.

Essentially there are two aspects to it – there is the tongue itself, and the tongue’s coating. Changes in the shape and colour of both of these aspects give us important information about the different organs of the body. These are the functions of the organs of the body according to Chinese Medicine, and do not necessarily correspond with the functions of the organs according to modern medicine.

Tongue Colour

The main parameters in looking at the tongue itself (as opposed to the tongue coating, which is addressed below) are shape and colour.

Tongue color: It can be generally divided into white (pale), pink, red, purple and, rarely – green. Except for pink (淡红 ), which is the normal tongue color , the rest indicate various kinds of disease.

“White”, or Pale (淡白) tongue:

The tongue is lighter than the normal pink tongue, and in severe cases may lack any pink colour at all, which is called a pale white tongue. Due to the decline of the function of Yang, Blood circulation and volume is also impaired, so that the Blood cannot suffuse the tongue, which is therefore light-coloured and “white”. Therefore, this tongue indicates internal Cold or Deficiency of qi and Blood.

Red(紅)tongue:

The tongue is bright red, and deeper in colour than the normal pink tongue. Because of Heat, Qi and Blood are “boiling”, and the meridians and vessels in the tongue are filled with blood, causing the tongue to be bright red. A very common cause of Heat leading to a red tongue is emotional discomfort of any kind.

Crimson ( 绛) Tongue

This tongue is a deeper red than the red tongue above.It can be seen in patients with fever from viral and bacterial infections, or in cases of Yin Deficiency Heat, such as in peri-menopausal syndromes, though Yin Deficiency Heat is not only seen in gynaecological conditions and can affect men as well as women.

Purple( 紫) tongue

The purple tongue is always caused by poor blood circulation. This can be caused either by Cold or Heat. Heat injures fluids and impedes blood circulation by reducing its fluid content so that it does not flow properly, in which case the tongue will be purple and dry and withered. Cold impedes blood circulation by making it more viscous, and in this case and the tongue is light purple or cyan purple and moist.

Blue-Green (青) tongue:

This tongue not red or pink at all, and is a blue-green colour. I. Ancient books describe it as the “tongue of the water buffalo”. I have never seen a water buffalo’s tongue but I presume it is a blue-green colour. Because of Cold and excess yin, the Yang is depressed, and the blood coagulates and stagnates (because Yang cannot push it along), so the tongue is blue.

Tongue Shape

Tongue shape: refers to the shape of the tongue body, including abnormal changes such as “fat and thin” ie too big and too small, swollen, cracked, tooth-marked, etc.

Enlarged 胀大 tongue:

There are two types of enlarged tongue – “fat” 胖大 tongue and 肿胀swollen tongue. Most Western practitioners conflate the two because only Chinese language books distinguish between them. The fat tongue and the swollen tongue are both larger than the normal tongue, and in severe cases may fill the whole mouth making it difficult to close, or there may be teeth indentations at the side of the tongue, though teethmarks are not a sign of severity, and are in fact exceedingly common.

The swollen tongue is mostly caused by heat and alcoholism, causing swelling of the tongue, and more major heat syndromes or poisoning. It definitely represents a severe condition, not least because the individual is unable to close their mouth

The fat tongue type is caused by water retention or phlegm and dampness. A necessary precursor to dampness and water retention is something called Qi Deficiency – when the body’s vital energy (or Qi) is not present in the body in sufficient amounts, then it fails to control the amount of fluids in the body, and the body becomes waterlogged, as it were. Probably this is the reason for the controversy among different sources as to whether a fat tongue is caused by Qi Deficiency or Dampness.

While it may not be a catastrophic error to confound the cause of the fat tongue, it can in fact result in a more accurate and efficacious treatment if one strives to be very precise. So here is the relevant passage from the standard Chinese textbook on Diagnosis, by the legendary, late Professor Deng Tie Tao, who died at the age of 103 in 2019, and who was my teacher’s teacher:

胖大舌。多因水饮痰湿阻滞所致。肿胀舌，多因热毒、酒毒致气血上壅，致舌体肿胀，多主热证或中毒病证。

the Fat Tongue: is caused by the stagnation/retention of fluids and dampness. The Swollen Tongue: is caused by Toxic Heat, Alcohol Toxins causing Qi and Blood to be blocked in the upper body.

So there we have it – no mention of Qi Deficiency. The practical consequence is that in patients with a fat tongue, we must clear Damp and Phlegm, not only increase Qi.

Thin 瘦薄 Tongue

The thin tongue is always caused by insufficient qi and blood and fluids which cannot fill the tongue. In a sense, it is the opposite of an enlarged or swollen tongue (see above）

Cracked 裂纹 Tongue:

There is a crack, or cracks on the tongue, and those cracks are not covered by tongue coating. It is mostly caused by damage to Blood, and body fluids. However, roughly 0. 5% of people have longitudinal and horizontal deep grooves on the tongue, which is called congenital tongue fissure. The cracks are mostly covered with tongue coating (unlike the pathological cracked tongue), and there is no other discomfort or symptoms in the body, and therefore the congenitally fissured tongue is not a sign of disease.

Teeth-mark 齿痕 Tongue:

There are traces of teeth imprinting on the edge of the tongue, so they are called teeth-marks on the tongue. The cause is that Spleen Deficiency cannot promote water metabolism, so the fluids accumulate and make the tongue fat, and therefore tooth marks appear where the sides of the tongue are squeezed against the teeth. Therefore, tooth marks are often seen with the fat tongue, and it indicates Spleen Deficiency or Dampness (and there is a causal relationship between the two).

Tongue Coating

The normal coating is thin and white. One kind of abnormal coating is thus thick and white. The definition of an abnormally thick tongue coating is one in which you cannot see the tongue surface underneath it. Thus a thick white coating can easily be mistaken for a pale / white tongue, but if a practitioner makes this mistake, which they often do, and prescribes herbal medicine, they are likely to prescribe the wrong medicine and thereby cause side effects. With acupuncture the danger of making mistakes is less, but there is always the danger of giving a weak and useless treatment, if the diagnosis is not accurate.

The thin white coating is a normal coating. The thick white coating indicates fluid retention or Dampness. The thin yellow coating indicates Heat. The thick yellow coating indicates Damp&Heat. And absence of tongue coating indicates Deficiency of Yin.

Changes in the tongue coating, for example from thick to thin, usually accompany significant improvements in symptoms. For example, the depression patient that I wrote about in another article, was also suffering from an upset stomach as a result of traveling in a country which has left than perfect food hygiene procedures. This is probably the reason why he had a thick yellow tongue coating when he came to see me. His actual tongue colour though was red, especially at the sides and tip, which is very common in anxiety and depression and even just day to day stress.

He preferred herbal medicine to acupuncture, so I prescribed a particular herbal formula, and he reported that for the first 3 days nothing very dramatic happened, but by the 4th day, both the depression and the upset stomach suddenly stopped and he noticed at the same time his tongue coating was suddenly much less thick.

Tongue Diagnosis Chart

Lastly, apart from changes in tongue colour and tongue shape and tongue coating colour and thickness, there is one aspect of tongue diagnosis which makes it much more specific and useful to us. Where exactly on the tongue these changes occur gives us a clue as to which organ systems of the body are imbalanced. The position of the organs on the tongue is fixed, and roughly corresponds to the position of these organs in the body, if you remember that the tip of the tongue represents the top of the body, and the root of the tongue represents the lower part of the body: