Vitamin B12 deficiency

Vitamin B12 is needed for blood and for the nervous system. It comes almost only from animal foods and needs a healthy stomach to be absorbed. Deficiency becomes more common with age: in the UK it affects more than one in ten people aged 75 or older.

Symptoms

• tiredness, breathlessness, pallor, as in any anaemia;
• a sore, red or smooth tongue, mouth ulcers;
• pins and needles, numbness or burning in both feet or both hands, the same on both sides;
• unsteady walking, memory problems, mood changes.

The NICE guideline admits its symptom list comes from expert experience, not studies. That is why it recommends testing when there is at least one symptom and at least one risk factor.

Neurological symptoms are a reason to see a doctor without delay. Nerve damage from low B12 can become permanent if treatment waits.

Who is at risk

• a vegan diet without B12 supplements or fortified foods;
• metformin;
• years of stomach-acid reducers;
• stomach or bowel surgery, Crohn’s disease, coeliac disease;
• pernicious anaemia or other autoimmune conditions in you or your family;
• recreational nitrous oxide (“laughing gas”), which inactivates B12 and can cause severe nerve damage even in young people;
• age 65 or older.

Which test to ask for

Total or active B12 (holotranscobalamin), always together with folate, because both deficiencies look the same on a blood count.

Pitfalls:

• a borderline result needs a second test, methylmalonic acid (MMA);
• if you already take B12 or a multivitamin, the result will read high: tell the doctor.

What not to do

Do not start folic acid without checking B12: it corrects the anaemia but does not protect the nerves, so a B12 deficiency goes unnoticed.