Severe vitamin B12 deficiency can also cause neurological problems, such as confusion, dementia, depression, and memory loss, according to the National Heart, Lung and Blood Institute (NHLBI).
Other symptoms of vitamin B12 deficiency involve the digestive tract, says NHLBI.
According to the health body, these symptoms include nausea (feeling sick to your stomach) and vomiting, heartburn, abdominal bloating and gas, constipation or diarrhoea, loss of appetite, and weight loss.
An enlarged liver is another symptom and a smooth, thick, red tongue are also signs of low B12 levels, it explains.
“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,” explains the NHS.
Why do some people struggle to get enough B12 in their diet?
Vitamin B12 is found naturally in a wide variety of animal foods and is added to some fortified foods.
As the National Institutes of Health explains, plant foods have no vitamin B12 unless they are fortified.
If you are looking for vegan and vegetarian-friendly alternatives, yeast extract (including Marmite), as well as some fortified breakfast cereals and soy products include B12, adds the NHS.