Vitamin B12 deficiency

Also called Pernicious anaemia, B12 deficiency

Cheap to treat, and if it is left too long the nerve damage does not come back.

What it is

Vitamin B12 is needed to make red blood cells and to maintain the myelin sheath around nerves. Without it, both fail.

Pernicious anaemia is the autoimmune cause: the stomach stops making the intrinsic factor needed to absorb B12. Other causes include a vegan diet without supplementation, metformin, long-term acid suppression, and gut surgery or disease.

The reason this matters urgently is neurology. B12 deficiency causes nerve damage, and if treatment is delayed, some of that damage is permanent. The blood picture is not a reliable guide either: neurological damage can occur before anaemia appears.

That is why a normal full blood count does not rule it out, and why treating on the basis of symptoms is sometimes the right call.

Signs you might notice

Fatigue, breathlessness, pallor.

Pins and needles, numbness, and a burning sensation in the hands and feet.

Unsteady walking, poor balance, and clumsiness.

Sore red tongue, mouth ulcers.

Memory problems, confusion, low mood, and irritability, which in an older person get attributed to dementia.

Cognitive symptoms in an older person always deserve a B12 test.

How it can affect day-to-day life

The commonest failure is stopping injections or being told a level is now normal. In pernicious anaemia the absorption problem does not go away, so treatment is lifelong.

The second commonest is under-treatment: some people need more frequent injections than the standard schedule, and the guidance allows for that where neurological symptoms are present.

Testing after starting treatment is misleading, which is why the diagnosis should be made before supplementation begins.

Supporting someone well

Treat promptly if symptoms suggest deficiency, particularly neurological ones. Delay costs nerve function permanently.

Continue lifelong treatment in pernicious anaemia. Do not stop because a level is normal; the level is normal because of the treatment.

Check B12 in anybody with unexplained neurological symptoms, cognitive change, or who takes metformin or long-term acid suppression.

Check it in vegans and in people after gut surgery.

Ask for more frequent injections if neurological symptoms persist; the BNF allows this.

In a service, put B12 injections on the medication record with their due dates. Fiducia Together schedules them, which is what stops a three-monthly injection quietly becoming a six-monthly one.

Where to get help

A GP diagnoses and treats this. Ask for the actual number and for intrinsic factor antibodies if pernicious anaemia is suspected.

The Pernicious Anaemia Society support people whose treatment is inadequate and their material is useful in consultations.

New neurological symptoms need prompt assessment rather than waiting for the next blood test.