Vitamin B12 deficiency can occur if a person isn’t getting enough of the vitamin in their diet, and left untreated, complications such as vision problems, memory loss, an abnormally fast heartbeat and loss of physical co-ordination can occur.

It’s best gained through foods of an animal origin, such as meat, salmon, milk and eggs, which means vegans and vegetarians may be at risk of becoming vitamin B12 deficient.

Also, some medical conditions can affect a person’s absorption of B12, including pernicious anaemia.

Chapped lips have also been linked to deficiency in other B vitamins, including vitamin B9 (folate), vitamin B12 (riboflavin) and vitamin B6.

A zinc deficiency can also cause chapped lips, as well as dryness, irritation and inflammation on the sides of the mouth.

Many of the symptoms improve with treatment, but some problems caused by the condition can be irreversible if left untreated.

The NHS warns: “The longer the condition goes untreated, the higher the chance of permanent damage.”

The NHS advises: “If your vitamin B12 deficiency is caused by a lack of the vitamin in your diet, you may be prescribed vitamin B12 tablets to take every day between meals.

“People who find it difficult to get enough vitamin B12 in their diets, such as those following a vegan diet, may need vitamin B12 tablets for life.

“Although it's less common, people with vitamin B12 deficiency caused by a prolonged poor diet may be advised to stop taking the tablets once their vitamin B12 levels have returned to normal and their diet has improved.”

If your vitamin B12 deficiency is not caused by a lack of vitamin B12 in your diet, you’ll usually need to have an injection of hydroxocobalamin every two to three months for the rest of your life.