Vitamins & iron · Blood test
Vitamin B12 blood test: normal range explained
Also printed as: Cobalamin, Vit B12, B12, Vitamin B-12
Vitamin B12 (cobalamin) is a vitamin your body needs to make red blood cells and keep nerves healthy; the test measures the amount in your blood in pg/mL. The adult range MedlinePlus prints is 299–1054 pg/mL, or 219–773 pmol/L; Indian labs often print a different range, but the range printed on your own report is the one that applies.
Last updated 5 sources
What is the normal range for vitamin B12?
| Printed for | Range |
|---|---|
| Adults, as MedlinePlus prints it | 299–1054pg/mL |
| In pmol/L, as MedlinePlus prints it | 219–773pmol/L |
Reference ranges vary between laboratories. Always use the range printed on your own report. Why ranges differ between labs
Sources:MedlinePlus
What does vitamin B12 measure?
The vitamin B12 test measures the amount of B12 (cobalamin) in your blood, reported in pg/mL or pmol/L. MedlinePlus says B12 helps keep your nerves and blood cells healthy, and Testing.com adds that it helps make DNA. It is often measured together with folate (vitamin B9), because the two work together to make new cells.
A serum B12 level has limits as a marker of what your cells can use: Lab Tests Online UK says it does not directly show whether active B12 is lacking in cells, and MedlinePlus says experts are not sure what a normal level is for some B vitamins. Second-line tests, such as methylmalonic acid, can help.
Why do doctors order the vitamin B12 test?
Doctors order B12 for symptoms of a possible deficiency, such as tiredness, numbness or tingling in the hands and feet, balance problems, memory changes or an irregular heartbeat, and when a CBC shows large red cells (MCV high) or anaemia. NHS says a GP can often diagnose B12 or folate deficiency anaemia from symptoms and blood tests.
Risk groups that prompt testing include people who eat no animal products, older people, anyone with memory, confusion or mood changes, people with coeliac or Crohn's disease or past stomach surgery, and people on long-term metformin, proton pump inhibitors or H2 blockers. The test is also used to follow treatment of a known deficiency.
What can change your vitamin B12 result?
Several things move a B12 result without a true change in what your body has.
- Pregnancy and oral contraceptives can lower the measured level, which Lab Tests Online UK says does not necessarily mean a true deficiency.
- Medicines that reduce absorption, such as metformin, proton pump inhibitors, H2 blockers, colchicine, phenytoin and some antibiotics, can lower it over time.
- Recent B12 supplements or injections raise the result, and biotin supplements can interfere with some assays.
- Alcohol reduces absorption of B12 and folate, and liver disease can raise the level.
- Taking folic acid alone when both are low can mask B12 deficiency on a blood count while nerve damage continues.
- Do not stop any medicine without talking to your doctor first.
How do you read vitamin B12 on your lab report?
Reports print the test as Vitamin B12, Vit B12 or Cobalamin, in pg/mL or sometimes pmol/L, often beside folate and the CBC. Testing.com says reference ranges differ between labs and to use the range printed on your report; MedlinePlus says labs use different normal ranges for B vitamins.
A value near the bottom of the range can still go with symptoms, and NHS notes some people have symptoms with normal levels while others have low levels and none. Your doctor reads it with haemoglobin, MCV, folate and your symptoms, and may add methylmalonic acid or homocysteine tests.
Amara reads vitamin B12 with the range printed beside it on each report, flags a value outside that range, and shows what changed since your last report. Try it with two sample reports
A sample Amara row for Vitamin B12: 203 pg/mL on 27 Jan 2026 at Lab A (sample), then 342 pg/mL on 18 Aug 2026 at Lab B (sample), each with its lab's printed range.
Questions people ask about vitamin B12
Is vitamin B12 the same as cobalamin?
Vitamin B12 and cobalamin are the same vitamin, and lab reports use either name; MedlinePlus writes B12 (cobalamin), and Testing.com says the test measures total circulating cobalamin. The number on the report is the amount of the vitamin in your blood, in pg/mL or pmol/L, and it is often printed beside folate.
Do I need to fast for a vitamin B12 test?
Fasting instructions for B12 differ between sources: Testing.com and Lab Tests Online UK say no fasting is needed for a standalone B12 test, while MedlinePlus says you may be asked not to eat or drink for 6 to 8 hours. Follow the instructions your own lab gives, and mention any B12 supplements or injections.
Why do vegetarians get a B12 test more often?
Vegetarian and vegan diets are listed by Testing.com and MedlinePlus among the reasons to test B12, because the vitamin comes mainly from animal products such as meat, eggs and dairy, so people who eat none of them can run low over time. Long-term metformin or acid-reducing medicines are other common reasons.
What does a low vitamin B12 on my report mean?
Low vitamin B12 means the value is below the range your lab printed. MedlinePlus lists low dietary intake, poor absorption from coeliac or Crohn's disease, lack of intrinsic factor and some medicines among the reasons, and says deficiency should be confirmed with a methylmalonic acid test. Your doctor reads it with your CBC, symptoms and history.
Sources
- Vitamin B TestMedlinePlus · medlineplus.gov · Opened
- Vitamin B12 levelMedlinePlus · medlineplus.gov · Opened
- Vitamin B12 Test: Check Your Levels, Get ResultsTesting.com · testing.com · Opened
- Vitamin B12 and FolateLab Tests Online UK · labtestsonline.org.uk · Opened
- Vitamin B12 or folate deficiency anaemia - DiagnosisNHS · nhs.uk · Opened
About this page
Every statement on this page comes from the sources listed above. Ranges are those commonly printed on Indian lab reports; the range printed on your own report is the one that applies.
Published by Amara Health, a product of MetaNova AI Private Limited, Hyderabad.
Amara Health does not provide medical advice, diagnosis or treatment. Information shown by Amara is based on available health records and may contain errors. Review important information against the original report and consult a qualified healthcare professional for medical decisions. Do not use Amara for medical emergencies.
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