Vitamin B12 is essential for a number of bodily functions.
As well as keeping your body's blood and nerve cells healthy, it also helps prevent anaemia - which can make people feel tired and weak. Common symptoms of a vitamin B12 deficiency include fatigue, pins and needles, and weight loss.
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But two signs that show up in your mouth can also suggest you are lacking the nutrient. A sore and red tongue, medically referred to as glossitis, could be a sign of a deficiency - according to NHS guidance.
When a person has glossitis, the tongue changes colour and shape, making it painful, red and swollen. The inflammation also makes the tongue look smooth, as the tiny bumps on the tongue that contain the taste buds stretch out and disappear.
Mouth ulcers are also a potential symptom. Those who don't get enough B12 can develop anaemia, and an additional symptom of this is a reduced sense of taste.
Some people develop a vitamin B12 deficiency as a result of not getting enough vitamin B12 from their diet. A diet that includes meat, fish and dairy products usually provides enough vitamin B12, but people who do not regularly eat these foods can become deficient.
Vitamin B12 deficiency anaemia is usually treated with injections of vitamin B12.
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