B12 deficiency is one of the most frequently found — and most frequently missed — results in India, partly because its early signs are so easy to dismiss.
What B12 does and where it comes from
Vitamin B12 is needed to make red blood cells, to build DNA, and to maintain the myelin sheath that insulates nerves. That last role is why deficiency can cause neurological symptoms, not just anaemia.
B12 occurs almost exclusively in animal foods — meat, fish, eggs and dairy. Plants do not reliably produce it. This is the single biggest reason deficiency is common in India, where a large share of the population is vegetarian or eats very little animal protein.
Commonly used ranges
A serum B12 in the borderline zone does not settle the question by itself. When symptoms suggest deficiency despite an apparently acceptable level, doctors may order methylmalonic acid or homocysteine, which rise early in true tissue deficiency.
Cut-offs vary by laboratory and assay; borderline results are interpreted alongside symptoms.
Who is at higher risk
- Long-term vegetarians and vegans, and their breastfed infants
- People on metformin for diabetes — long-term use reduces B12 absorption, a well-recognised interaction that is easy to overlook
- Long-term users of acid-reducing medicines such as proton pump inhibitors
- Adults over 60, in whom stomach acid and absorption decline
- Anyone with coeliac disease, Crohn disease, or previous stomach or intestinal surgery
- Pernicious anaemia, an autoimmune condition affecting the absorption factor B12 needs
Why the neurological symptoms matter most
Nerve damage from prolonged B12 deficiency can become permanent if left untreated for long enough, which is what makes early identification worthwhile. Importantly, folic acid supplementation can correct the blood picture while the nerve damage quietly continues — so B12 should be checked before treating a macrocytic anaemia with folate alone.
- Tingling, numbness or a pins-and-needles feeling in the hands and feet
- Balance problems or unsteadiness when walking
- Memory difficulty, poor concentration, low mood or irritability
- A sore, smooth or burning tongue, and mouth ulcers
- Fatigue and breathlessness if anaemia has developed
What to ask your doctor
- Do I need injections, or will oral supplementation be enough?
- Should we look for an absorption problem rather than assume it is dietary?
- I take metformin — should my B12 be monitored regularly?
- Should folate and iron be checked at the same time?
Common questions
Can vegetarians get enough B12 from food?
It is difficult. Dairy and eggs contain some B12, so lacto-ovo vegetarians fare better than vegans, but many still fall short over years. Fortified foods and supplements are the reliable route. Anyone following a strict vegetarian or vegan diet long term should have B12 checked periodically rather than assuming intake is adequate.
Does metformin really cause B12 deficiency?
Long-term metformin use is associated with reduced B12 absorption and is a recognised cause of deficiency. It is not a reason to stop the medication on your own — metformin is a valuable diabetes treatment. It is a reason to ask your doctor to monitor B12 periodically.
How long does treatment take to work?
Blood counts typically begin improving within a few weeks. Neurological symptoms respond more slowly, sometimes over months, and symptoms present for a long time before treatment may not fully reverse — which is the main argument for not delaying.
This article is general health information, not medical advice. Reference ranges differ between laboratories — always read the range printed on your own report and discuss results with a qualified doctor.
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