Vitamin B12 Level Reference Guide
See whether your vitamin B12 level is low, borderline or normal, and why it matters.
These health tools are still being tested and are updated regularly to give you a better experience. Results are estimates for information only — please confirm important results with a doctor. Read the medical disclaimer
Vitamin B12 Level Reference Guide
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About the Vitamin B12 Level Reference Guide
B12 deficiency is common among vegetarians and people on long-term metformin or acid-reducing medicines. It can cause anaemia and nerve problems.
How to use the Vitamin B12 Level Reference Guide
- Enter your serum vitamin B12 result.
- Choose pg/mL or pmol/L, and optionally your diet type.
- Press “Check B12”.
Reference ranges & how it works
Typical serum B12 ranges (lab-dependent):
Below 200 pg/mL — deficient · 200–300 pg/mL — borderline · about 300–900 pg/mL — normal
pmol/L = pg/mL × 0.738
In borderline cases, doctors may check methylmalonic acid (MMA) or homocysteine.
Worked example: Vitamin B12 Level Reference
A vegetarian with B12 of 250 pg/mL (185 pmol/L) is in the borderline range. Her doctor may check homocysteine or methylmalonic acid to confirm whether she is truly deficient.
Important limitations
- Serum B12 is an imperfect marker; symptoms can occur with “normal” levels.
- Recent supplements raise blood levels before stores recover.
- Reference ranges differ between laboratories; the range printed on your own report takes priority. Discuss abnormal results with a doctor.
Frequently asked questions
Who is at risk of B12 deficiency?
Vegetarians and vegans, older adults, people with stomach or gut problems and people taking metformin or acid-reducing medicines for a long time.
What foods have vitamin B12?
Milk, curd, paneer, eggs, fish, meat and fortified foods. Plant foods have almost none, so vegetarians may need supplements.
Does metformin cause low B12?
Yes, long-term metformin use reduces B12 absorption in a significant number of people. Guidelines suggest checking B12 periodically in people on metformin, especially if they have tingling or anaemia.
Are B12 injections better than tablets?
For most people, high-dose tablets work well. Injections are used when absorption is severely impaired (pernicious anaemia, after some stomach surgery) or for severe deficiency with nerve symptoms.
Sources
- Devalia V et al. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. Br J Haematol 2014;166:496-513.
- American Diabetes Association. Standards of Care 2024 (metformin and B12).
Medical disclaimer: These tools give general information and estimates only. They are not a diagnosis and do not replace advice from a qualified doctor. Always talk to your doctor about your results, and seek urgent medical help in an emergency. In an emergency call 112. Medical disclaimer · Terms of use · Privacy policy
