What is a Vitamin B12 test?
The Vitamin B12 (cobalamin) blood test measures how much B12 is circulating in your blood. B12 is found almost exclusively in animal products — meat, fish, eggs and dairy — so vegetarians and vegans are at particularly high risk of deficiency. In India, deficiency affects an estimated 47% of the population. Results are reported in pg/mL or pmol/L.
Vitamin B12 Normal Range
| Level | Value (pg/mL) | What it means |
|---|---|---|
| Severely Deficient | < 100 | Critical — needs urgent treatment |
| Deficient | 100 – 200 | Low — treatment needed |
| Borderline / Grey Zone | 200 – 300 | Possibly low — symptoms may occur |
| Normal | 300 – 900 | Normal |
| High | > 900 | Investigate if not on supplements |
What does LOW Vitamin B12 mean?
LOW B12 below 200 pg/mL — Deficiency
Low B12 is called deficiency or cobalamin deficiency. In India, the most common causes are: strictly vegetarian/vegan diet (no B12 from plant foods), poor absorption (pernicious anaemia, celiac disease, Crohn's disease, after gastric surgery), long-term use of metformin (a diabetes drug) or antacids/PPIs, and old age (stomach produces less acid to absorb B12). Symptoms include extreme fatigue, weakness, tingling or numbness in hands/feet, memory problems, depression, a sore tongue and megaloblastic anaemia.
What does VERY LOW Vitamin B12 mean?
LOW B12 below 100 pg/mL — Severe Deficiency
Severe B12 deficiency can cause irreversible nerve damage (subacute combined degeneration of spinal cord), psychiatric symptoms, and severe megaloblastic anaemia. At this level, your doctor will usually start B12 injections (cyanocobalamin or methylcobalamin) rather than tablets, as absorption through the gut may be impaired.
What does HIGH Vitamin B12 mean?
HIGH B12 above 900 pg/mL
High B12 in someone taking supplements is usually harmless — excess B12 is excreted in urine. However, unexpectedly high B12 (especially above 1000 pg/mL) without supplements can occasionally indicate liver disease, myeloproliferative disorders or certain cancers. Your doctor will assess whether further investigation is needed based on other symptoms and tests.
Who is at risk of B12 deficiency in India?
- Strict vegetarians and vegans — no B12 in plant foods
- Elderly people — reduced stomach acid means less absorption
- People taking metformin for diabetes long-term
- People on long-term antacids (omeprazole, pantoprazole)
- People with pernicious anaemia (autoimmune condition)
- Post gastric surgery or gastric bypass patients
Questions to ask your doctor
- Do I need injections or tablets?
- Is my metformin or antacid causing this?
- Should I check folate (B9) and iron too?
- When should I retest?