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Vitamin B12 deficiency: the symptoms and what they mean | CION Cancer Clinics
Vitamin B12 deficiency most often causes tiredness, breathlessness on effort, pale skin and tingling or numbness in the hands and feet. A sore red tongue, mouth ulcers, poor memory and low mood are also common. The symptoms build slowly and are easily blamed on age or stress. This page explains each group of symptoms, which ones need a doctor the same day, and how a blood test confirms it. At CION Cancer Clinics, our haematologist cares for anaemia, bleeding, clotting and inherited blood disorders, with ArogyaSri, CGHS and cashless insurance accepted.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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The short answer
What are the symptoms of vitamin B12 deficiency?
The most common symptoms are tiredness, breathlessness on effort, pale skin and tingling or numbness in the hands and feet. Many people also notice a sore red tongue, mouth ulcers, poor memory or low mood.
Why the symptoms are so easy to miss
Your liver holds a store of B12. When intake or absorption falls, that store runs down slowly, often over years. The symptoms creep in so gradually that people put them down to work, age, heat or stress. By the time a blood test is done, the tiredness may have been there for a long time.
Two ways B12 shortage shows itself
B12 is needed to make healthy red blood cells and to keep the nerves working. So the symptoms come from two places. When red cells are affected, your haemoglobin falls and you feel tired and short of breath. When nerves are affected, you get pins and needles, numbness or unsteady walking. These two do not always travel together. Some people have nerve symptoms with a normal haemoglobin, and a normal blood count does not rule B12 shortage out.
A symptom list cannot diagnose you. The same symptoms come from thyroid problems, low iron, diabetes and many other causes. A blood test is what settles it.What people notice
Which parts of the body does low B12 affect?
Most people have symptoms from more than one group. Tick off what you recognise and take the list to your doctor.
Blood
Red cells come out larger than normal and too few of them are made. Less oxygen reaches your muscles and brain.
You may notice
- Tiredness that sleep does not fix
- Breathlessness on stairs
- Pale or slightly yellow skin
- A racing heartbeat
Nerves
B12 protects the coating around nerves. When it runs low, messages along the nerves slow down or go wrong.
You may notice
- Pins and needles in feet or hands
- Numbness or burning feet
- Poor balance, especially in the dark
Mouth and gut
Cells lining the mouth and gut renew quickly, so they feel the shortage early.
You may notice
- A smooth, sore, red tongue
- Mouth ulcers that keep coming back
- Loss of appetite and weight
Mind and mood
Families often notice these first, before the person does. In older adults they can be mistaken for ageing.
You may notice
- Forgetfulness and poor focus
- Irritability or low mood
- Confusion in more severe cases
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Symptoms that need a doctor the same day
If walking has become unsteady, legs feel weak, numbness is spreading quickly, or there is new confusion, see a doctor the same day. Nerve damage from low B12 is more likely to recover when it is treated early. If there is chest pain, fainting or breathlessness at rest, go to the nearest emergency department or call 108. Do not wait for a routine appointment.
From symptom to answer
How do doctors confirm low B12?
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A conversation and an examination
Your doctor asks about diet, medicines, stomach surgery and family history. They check your tongue, skin, reflexes, balance and feeling in your feet.
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A complete blood count
This shows your haemoglobin and the size of your red cells, written as MCV. Large red cells point towards B12 or folate shortage, though other causes exist too.
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B12 and folate levels
Both are usually checked together, because the two shortages look alike on a blood count. If you can, have the test before anyone starts you on B12, because treatment changes the result.
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Extra tests if the result is borderline
Some results sit in a grey zone. Your doctor may then order further blood tests, or simply repeat the level alongside how you feel.
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Finding the cause
Low B12 is a finding, not a full diagnosis. Your doctor looks for why: diet, a medicine, or a problem absorbing B12 from the gut.
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Who is more likely
Why do some people run low on B12?
There are two broad reasons. Either too little B12 goes in, or the body cannot absorb what goes in. The treatment and how long it lasts depend on which one it is.
Too little in the diet
B12 comes almost only from animal foods such as milk, curd, eggs, fish and meat. Many families in Telangana and Andhra Pradesh are fully vegetarian, and some take very little dairy. This is one of the commonest reasons for low B12 in India.
Trouble absorbing it
The stomach needs acid and a special protein, called intrinsic factor, to absorb B12. An autoimmune condition can stop that protein being made. Long-term metformin for diabetes, long-term acid-reducing medicines, stomach or bowel surgery and some gut conditions also reduce absorption. Older adults absorb less as stomach acid falls.
What this page cannot tell you
It cannot tell you whether your tiredness is B12 or something else, or which cause applies to you. Keep taking every prescribed medicine, including metformin, and ask your doctor about testing instead.
Commonly believed
What do people get wrong about B12?
"Tingling in the feet is just age or sugar."
Diabetes and ageing do cause tingling. So does low B12, and the two can sit together, especially in people on metformin. It is worth a blood test rather than an assumption, because B12-related nerve damage can improve with treatment.
"My haemoglobin is normal, so my B12 must be fine."
Nerve symptoms can appear before the blood count changes. A normal haemoglobin is reassuring about the red cells, but it does not rule out low B12. If the symptoms fit, ask for the level itself.
"A multivitamin from the chemist will sort it out."
It may not, if the problem is absorption. Starting supplements before testing can also hide the result. Let a doctor find the cause first, then agree the treatment.
"Once I feel better, the problem is over."
Energy often returns before the stores are rebuilt. If the cause is an absorption problem, treatment may be long-term. Your doctor decides how long, based on the cause and repeat tests.
On your report
What do the words on a B12 report mean?
- Haemoglobin (Hb)
- The oxygen-carrying protein in red cells. Low haemoglobin is what makes you tired and breathless.
- MCV
- The average size of your red cells. A high MCV means the cells are larger than usual, which fits B12 or folate shortage but has other causes.
- Macrocytosis
- The medical word for large red cells. It is a description, not a diagnosis.
- Serum B12
- The B12 level in your blood. Reference ranges differ between laboratories, so read it against the range printed on your own report.
- Serum folate
- Another vitamin needed to make red cells. It is often low alongside B12, or instead of it.
Questions we are asked
Common questions about B12 deficiency symptoms
What is usually the first sign of low B12?
For most people it is tiredness that does not lift with rest, sometimes with breathlessness on stairs. Others first notice pins and needles in the feet or a sore tongue. Because these creep in slowly, family members often spot the change before the person does. None of them is specific, so a blood test is needed.
Can low B12 cause tingling even if my blood count is normal?
Yes. The nerves can be affected before the red cells change, so a normal haemoglobin does not rule it out. If you have numbness, burning feet or poor balance, ask your doctor to check the B12 level itself, not only the blood count. Tell them about any diabetes medicine you take.
Can B12 deficiency affect memory or mood?
It can. Poor concentration, forgetfulness, irritability and low mood are all described. In older parents these changes are easily blamed on age. A B12 test is simple and is usually part of the checks when memory changes. It is one possible cause among several, and a doctor should look at the whole picture.
Will the nerve symptoms go away with treatment?
Many people improve, particularly when treatment starts early. Nerve recovery is slower than blood recovery and is not always complete, especially after a long delay. That is why worsening numbness or unsteady walking should be seen promptly rather than watched for months. Your doctor will follow your symptoms at each visit.
Should I start B12 tablets myself before seeing a doctor?
It is better to be tested first. Starting B12 before the blood test can make the result look normal and hide the cause. If the problem is absorption, tablets bought over the counter may not be enough. A doctor can decide whether injections or tablets suit you and for how long.
Is low B12 a sign of blood cancer?
In most people, no. Diet, medicines and absorption problems explain the large majority. Large red cells with a normal B12 and folate, or other abnormal counts alongside, may need a haematologist to look further. The report on its own cannot tell you which applies, so take it to your doctor rather than searching for the worst case.
Which doctor should I see for B12 deficiency?
Your family doctor or physician can usually test and treat it. A haematologist, a specialist in blood disorders, becomes useful when the counts are very low, other blood cells are also affected, the cause is unclear, or treatment is not working. A neurologist may be involved when nerve symptoms are severe.
Is the B12 test covered by Aarogyasri or insurance?
Coverage for a standalone outpatient blood test varies. Aarogyasri, CGHS, ECHS, EHS, PM-JAY and cashless insurance each have their own rules, and those rules change. Check your current scheme or policy terms, or call the helpline with your card details and we will help you find out what applies.
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Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Sources
- NHS — Vitamin B12 or folate deficiency: symptoms
- NHS — Vitamin B12 or folate deficiency: overview
- NICE — Vitamin B12 deficiency in over 16s: identification and management (NG239)
- NHS — Vitamins and minerals: B vitamins and folic acid
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
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Talk to us
Have a blood report showing low B12 or large red cells?
Share it with us or call the helpline. Our haematology team will look at it with you and explain what the next step is. One helpline serves every CION centre.