Cracks in the tongue: why do they happen, and is it a vitamin deficiency?

The upper surface of the tongue is normally flat and covered with small bumps (papillae) that carry the taste buds. Cleveland Clinic defines fissured tongue as grooves and clefts on this surface, and writes that it is a healthy variation of normal, not a disease that needs treatment. Its medical names are lingua plicata and fissured tongue. The grooves can be as shallow as 2 millimetres or as deep as 6 millimetres.

The appearance varies from person to person. Cleveland Clinic gives the commonest appearance as a prominent groove running lengthways down the middle of the tongue with smaller cracks branching off to the sides; in some people the grooves cross one another and divide the tongue into small islands, while in others there are scattered lines that do not join up. The cause is unknown; the fact that it runs in families suggests genetics may play a part. The cracks do not go away, but nor is there anything that calls for getting rid of them.

There is data from Turkey. In a population survey in Istanbul in which 765 people selected by cluster sampling were examined using WHO criteria, fissured tongue was the commonest tongue finding at 5.2%; being 65 or older was a significant risk factor for it. Cleveland Clinic likewise writes that worldwide rates range from 2% to 20% depending on the study, that the cracks are slightly more common in men and over the age of 50, and that they can deepen with age.

Here is the distinction most Turkish sources miss: vitamin deficiency does not crack the tongue, it smooths it. With a lack of B12, iron or folic acid, the papillae on the surface of the tongue disappear and the tongue becomes smooth, bright red and burning; this is called atrophic glossitis (thinning of the tongue surface). The NHS lists a sore or red tongue among the symptoms of anaemia caused by B12 or folate deficiency, and a sore tongue among the symptoms of iron deficiency anaemia. In a study in China comparing 236 patients with atrophic glossitis with 208 healthy people, B12 deficiency was found in 68.22% of patients, low ferritin (iron stores) in 13.98% and anaemia in 21.61%; those with B12 deficiency responded well to supplements.

You can tell them apart at home like this. Stick your tongue out in the mirror in good light and look at three things. First, the surface: is the rest of the tongue rough, velvety and bumpy, or is it smooth and shiny in patches or all over? Second, the colour: apart from the cracks, is the tongue pink, or has it turned deep red? Third, time: have these cracks looked like this for years, or did you notice them in the last few weeks? Cracks in a pink, rough tongue that has not changed for years fit a structural variation. New smoothness, redness and burning, on the other hand, bring a blood test onto the agenda. The decision is made with a blood test and an examination.

A picture that often goes with fissured tongue is geographic tongue. The Oral Health Foundation defines geographic tongue as a common, harmless condition in which irregular, smooth red areas with white or pale borders form on the surface of the tongue, giving it the look of a map; it writes that these areas change shape and move around, and can sting with hot and spicy food. In a study in Erzurum that screened 7,619 dental patients, geographic tongue was seen in 1.5%, and 34.5% of these people also had fissured tongue. Geographic tongue was more common under the age of 30, in non-smokers and in people with a history of allergy.

Fissured tongue is seen more often alongside certain conditions. Cleveland Clinic lists them as geographic tongue, Melkersson-Rosenthal syndrome (a rare condition in which recurring swelling of the face and lips, facial palsy and fissured tongue occur together), Down syndrome, Sjögren syndrome, chronic granulomatous disease and psoriasis. In a study in Austria comparing 173 people with psoriasis and 173 healthy volunteers, fissured tongue was found in 14.4% of the psoriasis patients and 7.5% of the volunteers. Even so, Cleveland Clinic stresses that the cracks on their own are not a warning sign of any disease.

Dry mouth changes the picture. In a 2026 meta-analysis of Sjögren syndrome, an immune disease that affects the salivary glands, fissured tongue was found markedly more often than in healthy people; but because the confidence interval of the estimate is very wide, it would not be right to give an exact rate. Oral thrush, thinning of the tongue surface, cracks at the corners of the mouth and tooth decay were also more common in the same patients. The NHS writes that dry mouth is rarely a sign of something serious, but that you should see a doctor if you also have painful white patches in your mouth.

When do the cracks become a problem? Cleveland Clinic writes that fissured tongue usually causes no symptoms, but that when food debris and bacteria fill the grooves it can cause bad breath, swelling and inflammation of the tongue (glossitis) and a burning feeling. In this case the problem is not the crack itself but what collects inside it. Fissured tongue does not cause cancer; but an ulcer in one spot on the tongue that will not heal, a white or red patch, or a hard area is a separate matter and should not be brushed off as a crack.

The first list is the typical behaviour of fissured tongue; in this picture, good care is enough. If even one item from the second list applies, see your dentist or GP.

The sequence below moves from what you can observe at home to the assessment the clinician will carry out.

1. 1

   Look at the surface and colour in the mirror

   Stick your tongue out in good light. Is the surface outside the cracks rough and pink, or smooth and red? Are there map-like red areas with white edges? Take a photo; it is useful for comparing a few weeks later.

2. 2

   Check any single spot separately

   Look at the sides and underside of the tongue as well. Is there a single groove, ulcer, white or red patch, or an area that feels hard to the touch, that looks different from the rest? If there is an ulcer, note the date; if it goes beyond 3 weeks, see your dentist. For a red or white patch or a lump, do not wait 3 weeks; show it to your dentist.

3. 3

   Write down any accompanying symptoms

   Burning, dry mouth, dry eyes, tiredness, pins and needles in the hands and feet, cracks at the corners of the mouth, swelling of the lips, psoriasis. This list determines which tests the clinician will ask for.

4. 4

   An examination by your dentist

   The dentist examines the tongue, the inside of the mouth and the teeth. Cleveland Clinic writes that fissured tongue can be recognised just by looking, and is often noticed at a routine dental check-up. If a sharp tooth edge or an ill-fitting denture is rubbing against the tongue, this is also picked up at this stage.

5. 5

   A blood test if needed

   If the tongue has become smooth, red and burning, your GP requests a full blood count, B12, folic acid and ferritin. In the study in China, B12 deficiency and anaemia were more common in patients with thinning over more than half or all of the tongue surface.

6. 6

   Further assessment if needed

   For an ulcer or patch that will not heal, referral to oral and maxillofacial surgery or an oral medicine specialist and a biopsy; for dry mouth and dry eyes, rheumatology; for recurring facial swelling, dermatology or neurology. The question to ask: is this appearance a structural variation, or the mark of a disease?

Fissured tongue itself needs no treatment. What is done depends on the problem that comes with it.

The points below are wrong decisions often made with this complaint. We set them out so that you can ask the right questions whichever clinician you see.

The cracks themselves do not go away; what changes are the complaints that come with them. The plan of the clinician following you takes priority.

1. With regular tongue cleaning

   As the debris in the grooves is cleared, bad breath and burning ease. The cracks stay the same; Cleveland Clinic writes that they do not go away, but can be kept healthy.

2. With geographic tongue

   The Oral Health Foundation writes that the red areas change shape and move around over time. Flare-ups can come and go.

3. When a deficiency is treated

   With supplements, the burning and redness of the tongue are expected to recede. Your GP decides when to repeat the blood test.

4. If an ulcer has still not healed after 3 weeks

   This is no longer a picture to watch. See your dentist or GP.

We do not give a single figure here, because most cracks in the tongue need no treatment at all; the scope is set by the problem that comes with them. These are the items that determine it:

The accompanying problem

Fissured tongue on its own, a vitamin deficiency, oral thrush, dry mouth or an ulcer that will not heal are completely different routes.

The need for tests

An examination is usually enough; a blood test is added when a deficiency is suspected, and a biopsy for an ulcer that will not heal.

Sources of irritation in the mouth

If a sharp tooth edge or an ill-fitting denture is rubbing against the tongue, correcting it enters the plan.