Medically reviewed by Dr. Farhana Mukhtar, M.B.B.S., M.Phil (Pb.), Consultant Chemical Pathologist, Al-Nasar Lab & Diagnostic Centre. Updated September 2026.
Quick answer: Vitamin B12 is measured with a simple blood test. A level below about 200 pg/mL indicates deficiency, and 200 to 300 is borderline. Deficiency causes tiredness, tingling in the hands and feet, and memory problems. Untreated, the nerve damage can become permanent, which is why it should not be ignored.
Book a B12 test: call 0300 0341944, or arrange home sample collection across Lahore on 0309 1166944.
What does vitamin B12 do?
B12 has two jobs that matter clinically. It is needed to make healthy red blood cells, and it maintains the protective sheath around your nerves.
That second job is why B12 deficiency is more serious than most vitamin deficiencies. A shortage of iron makes you tired. A prolonged shortage of B12 damages nerves, and unlike the blood changes, that damage does not always reverse once treatment begins.
What are the symptoms of B12 deficiency?
- Persistent tiredness and weakness, often the first complaint
- Tingling, numbness or a pins and needles sensation in the hands and feet
- Poor memory, difficulty concentrating, mental fogginess
- A sore, smooth or red tongue, and sometimes mouth ulcers
- Unsteadiness or a change in the way you walk
- Pale skin, breathlessness on mild exertion
- Low mood or irritability
These are easily attributed to stress, workload or ageing, which is exactly why the deficiency runs undetected for years in many people.
What is a normal B12 level?
- Below 200 pg/mL: deficient
- 200 to 300 pg/mL: borderline, and often still symptomatic
- Above 300 pg/mL: generally considered adequate
Ranges vary between laboratories, so read the range on your own report. An important caveat: symptoms can appear while the blood level still reads borderline, so your doctor treats the patient rather than the number alone.
Who is most at risk in Pakistan?
B12 is found almost entirely in animal foods, which shapes who is affected here.
- People eating little or no meat, eggs, fish or dairy. Largely vegetarian diets carry a high risk unless supplemented
- Anyone taking metformin long term. This is a big one. Metformin is the most prescribed diabetes medicine in Pakistan and reduces B12 absorption over years. Anyone on it for a long period should have B12 checked periodically
- Older adults, whose stomachs produce less acid and absorb B12 less efficiently
- People with pernicious anaemia, an autoimmune condition blocking absorption
- Anyone who has had stomach or intestinal surgery
- People with coeliac disease, Crohn’s disease or long standing H. pylori infection
- Long term users of acid reducing medicines
- Pregnant and breastfeeding women, whose requirement rises
Why is B12 deficiency often missed?
There is a specific trap worth understanding. B12 deficiency causes a particular kind of anaemia in which the red cells become unusually large, showing on a complete blood count as a raised MCV.
Folate deficiency causes the same blood picture. If someone is given folic acid, the blood counts improve and everyone relaxes, while the B12 shortage continues quietly damaging nerves. This is why B12 and folate are usually measured together, and why an unexplained raised MCV should always prompt a B12 test rather than an assumption.
How is deficiency treated?
That is your doctor’s decision, but broadly it depends on the cause. Dietary shortage often responds to oral supplements. Absorption problems, including pernicious anaemia and post surgical cases, usually need injections, because tablets cannot be absorbed reliably.
Treatment is generally inexpensive and effective. Tiredness and blood counts improve within weeks. Nerve symptoms improve more slowly, and if they have been present a long time, some may not fully recover. That is the argument for testing early rather than waiting.
How to prepare
A blood sample is taken from a vein in your arm. Fasting is not usually required, though some laboratories prefer a morning sample.
One important point: tell your doctor if you have already started B12 supplements or had an injection recently. Either will raise the blood level and can produce a falsely reassuring result that hides a real underlying problem.
B12 testing at Al-Nasar Lab
Al-Nasar Lab & Diagnostic Centre has provided laboratory testing in Lahore since 1996 and holds ISO 15189:2022 accreditation from the Pakistan National Accreditation Council. Vitamin B12, folate, complete blood count and vitamin D testing are available at our main Johar Town campus and every collection centre, with home sample collection and same day digital reports.
Because persistent tiredness has several possible causes, B12 is often tested alongside thyroid function, iron studies and vitamin D from a single sample.
Find your nearest collection centre, see our full test list, or contact us to book.
Frequently Asked Questions
What is a normal vitamin B12 level?
Generally above 300 pg/mL. Below 200 is deficient and 200 to 300 is borderline, though ranges differ between laboratories.
Do I need to fast for a B12 test?
Usually not. Some laboratories prefer a morning sample, and fasting is only needed if the test is combined with others that require it.
Can metformin cause B12 deficiency?
Yes. Long term metformin use reduces B12 absorption, and it is a common and often overlooked cause in people with diabetes. Periodic testing is sensible if you have taken it for years.
Can B12 deficiency be reversed?
Tiredness and anaemia usually correct well with treatment. Nerve symptoms improve more slowly and may not fully resolve if the deficiency went untreated for a long time.
Is B12 deficiency common in vegetarians?
Yes. B12 occurs almost exclusively in animal foods, so people eating little or no meat, fish, eggs or dairy are at higher risk unless they supplement.
This article is for general information and is not a substitute for medical advice. Please discuss your results with a qualified doctor.
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