Health Library / Blood tests
Vitamin B12 deficiency: why it is common in India, and why it is missed
· 6 min read
Vitamin B12 deficiency is considerably more common in India than in most of the world, for a straightforward reason: B12 occurs naturally almost only in animal foods, and a large share of the population eats little or none.
It matters more than most vitamin deficiencies because of what it damages. Anaemia from B12 deficiency corrects readily. Nerve damage, if it has been present long enough, may not.
What it looks like
The blood picture is a macrocytic anaemia — large red cells, a raised MCV on the CBC — with tiredness, breathlessness and pallor.
The neurological picture is the one that matters most and is most often missed, because it can appear before any anaemia does. Tingling or numbness in the hands and feet, unsteadiness, difficulty with balance, memory problems and mood change are all recognised presentations. In an older adult these are frequently written off as ageing, and in a younger one as stress.
A sore, smooth tongue and mouth ulcers are common additional clues.
Who is at risk
Diet is the largest factor, so strict vegetarians and vegans are at substantially higher risk, and so are their breastfed infants if the mother is deficient. But absorption matters as much as intake.
Metformin, taken by a great many people with diabetes, reduces B12 absorption over years of use — a well-established interaction that is routinely forgotten. Long-term acid-reducing medicines do the same, because stomach acid is needed to release B12 from food. Older adults absorb it less well in general, and conditions such as pernicious anaemia, coeliac disease and Crohn's, or previous stomach or bowel surgery, all impair it.
- Vegetarian or vegan diet, and their breastfed infants
- Long-term metformin use
- Long-term proton pump inhibitors or other acid-reducing medicines
- Age over 60
- Pernicious anaemia, coeliac disease, Crohn's disease
- Previous stomach or intestinal surgery
Testing and correcting it
Serum B12 is the usual test. It has limits — it can read borderline when stores are genuinely low — so where the level is equivocal and symptoms fit, your doctor may add homocysteine or methylmalonic acid, which rise earlier and more specifically.
Correction is by supplements or injections depending on whether the problem is intake or absorption; someone who cannot absorb it will not be fixed by tablets alone. Anaemia responds within weeks. Neurological symptoms respond more slowly, sometimes only partially, and that gap is precisely why testing early rather than after months of tingling matters.
One important caution: folate supplements can correct the anaemia of B12 deficiency while the nerve damage continues underneath. That is why the two are tested and treated together rather than folate being given alone.
This article is general health information, not a diagnosis or a treatment plan. Test results are read alongside your symptoms and history — please discuss yours with your doctor. See our disclaimer.
