Vitamin B12 is essential for making red blood cells, keeping nerves healthy and producing DNA. Studies across India have found low B12 levels in a large share of adults, particularly among vegetarians, because the vitamin comes mainly from animal foods. Deficiency develops slowly and is easy to miss.
Understanding your result
| Serum B12 level | Commonly interpreted as |
|---|---|
| Below 200 pg/mL | Deficient |
| 200 – 300 pg/mL | Borderline; further tests may help |
| About 300 – 900 pg/mL | Usually adequate |
| Very high levels | Often due to supplements or injections; occasionally needs evaluation |
Because serum B12 is not a perfect test, doctors may also check methylmalonic acid (MMA) or homocysteine, which rise when the body is short of usable B12.
Signs and symptoms of deficiency
- Tiredness, weakness and breathlessness
- Tingling, numbness or burning in the hands and feet
- Poor balance or difficulty walking
- Memory problems, poor concentration or low mood
- A sore, smooth red tongue and mouth ulcers
- Pale or slightly yellow skin
On a CBC, B12 deficiency often shows as anaemia with large red blood cells (high MCV). Nerve damage can occur even before anaemia appears, and long-standing nerve damage may not fully recover, which is why early detection matters.
Who is at higher risk?
- Vegetarians and vegans, especially those who eat little dairy
- People taking metformin for diabetes for a long time
- Long-term users of acid-reducing medicines such as proton pump inhibitors
- Older adults, who absorb B12 less efficiently
- People who have had stomach or bowel surgery, or conditions such as pernicious anaemia
- Pregnant and breastfeeding women on vegetarian diets
Food sources
- Milk, curd, buttermilk, paneer and cheese
- Eggs
- Fish, chicken and meat
- Fortified foods such as some cereals and plant milks
Plant foods such as spinach and dal do not provide reliable B12. Strict vegetarians and vegans may need fortified foods or supplements.
Treatment
Depending on the cause and severity, doctors may prescribe oral B12 tablets, sublingual tablets or a course of injections, followed by a maintenance dose. If absorption is the problem, injections may be needed long term. Follow-up tests show whether levels are improving.
When to get tested
Ask your doctor about a B12 test if you have tingling, numbness, unexplained tiredness or anaemia, or if you are a vegetarian, on metformin or over 60.
Lab Tests Explained: the full series
- Part 1: CBC (Complete Blood Count)
- Part 2: Lipid Profile
- Part 3: Liver Function Test
- Part 4: Kidney Function Test
- Part 5: Urine Routine Test
- Part 6: Iron Studies and Ferritin
- Part 7: Vitamin B12 (you are here)
- Part 8: Full-Body Checkup by Age
Related reads: Blood sugar levels and HbA1c · Thyroid tests · Vitamin D test · Uric acid
Disclaimer: This article is for general information only and is not medical advice. Reference ranges vary between laboratories, so always read your report against the range printed on it and discuss results with a qualified doctor.
