Nutritionist Sarah Di Lorenzo: Why you need vitamin B12 and how to know if you’re not getting enough

Vitamin B12 is a vitamin you rarely think about when levels are healthy, but when they slip, the effects can ripple through the whole body. Symptoms can range from low energy and difficulty concentrating to changes in balance, mood and nerve function.

Vitamin B12 matters because it is essential for making healthy red blood cells, supporting the nervous system and helping the body synthesise DNA. When levels are too low, red blood cells can become large and ineffective, which is why people can feel tired, pale, short of breath and generally flat.

Low B12 can also affect the protective coating around nerves. This is why deficiency may show up as pins and needles, numbness, poor balance, memory problems or mood changes. In some people, nerve symptoms can appear even before anaemia is obvious.

One main reason B12 deficiency is so easy to miss is that it often develops slowly. The early symptoms can look a lot like everyday exhaustion — fatigue, weakness, brain fog, poor concentration or irritability. This can easily be put down to stress, ageing or simply being run down. As B12 deficiency progresses, neurological symptoms can appear. These include numbness, tingling, reduced coordination, visual disturbance and feeling less steady on your feet.

A sore, red tongue and mouth ulcers can also occur, which many people put down to low immunity or stress before considering B12 deficiency. These kinds of symptoms should not be brushed aside. Your body is sending you messages that should not be ignored. Long-standing deficiency can sometimes cause permanent nerve damage.

Because we cannot make vitamin B12 ourselves, we rely on diet or supplements. It is found naturally in animal foods such as meat, fish, eggs and dairy, and in fortified foods such as some breakfast cereals and plant-based milks. That means risk is higher in people who eat little or no animal food, in older adults, in people with coeliac or Crohn’s disease, after stomach or bowel surgery, and in those taking medicines that can reduce absorption - including long-term acid-suppressing drugs and metformin.

I recommend B12 supplementation for vegan patients, and for many vegetarians too depending on intake and blood levels, as most natural food sources come from animal products. Fortified foods can help, but they are not always enough on their own. It needs to become part of the daily routine.

If B12 deficiency is suspected, diagnosis usually starts with blood tests rather than guesswork. A doctor may check a full blood count, B12 levels and often folate, and sometimes follow-up testing is needed if results are borderline or symptoms strongly suggest deficiency.

Food can help prevent low intake, but when deficiency is confirmed, treatment may require supplements or injections depending on the cause.

A nutrient you should pay attention to is folate. B12 and folate are closely linked in red blood cell production and DNA synthesis, and deficiencies can overlap. That is one reason proper testing matters, because the symptoms can look similar but the treatment plan may differ. Folate deficiency can cause tiredness, weakness, pallor, shortness of breath, poor concentration, a sore tongue and mouth ulcers. Unlike B12 deficiency, it does not usually cause the same nerve symptoms such as pins and needles, numbness or balance problems.

Folate is found in green leafy vegetables such as spinach, kale and broccoli, as well as legumes, asparagus, avocado, citrus, nuts, seeds and fortified cereals and breads. If your diet is low in these foods, your folate intake may be falling short.

If your energy is persistently low, your thinking feels foggy, or you are noticing numbness, tingling, balance problems or a sore tongue, I recommend speaking with your GP, clinical nutritionist or dietician. Sometimes what feels like stress or burnout is actually a nutritional deficiency that deserves proper attention.