Healthwise says that if your vitamin B12 deficiency is mild, you may not have symptoms or you may not notice them.

If you have anaemia caused by a vitamin B12 deficiency, you may have other symptoms that affect your behaviour.

The NHS says: “Although many of the symptoms improve with treatment, some problems caused by the condition can be irreversible if left untreated.”.

NHS Inform says that although it's uncommon, vitamin B12 or folate deficiency can lead to complications, “particularly if you've been deficient in vitamin B12 or folate for some time”.

Nonetheless, it also says that most cases of vitamin B12 and folate deficiency can be easily treated with injections or tablets to replace the missing vitamins.

“If you have a vitamin B12 deficiency caused by pernicious anaemia, a condition where your immune system attacks healthy cells in your stomach,” explains the NHS