Vitamin B12 Test and Its Normal Range
B12 is checked with a simple blood test. Below 200 pg/mL is generally taken as a deficiency, with 200-300 considered borderline.
Vitamin B12 is measured with an ordinary blood test, often alongside a complete blood count, because a long deficiency changes the size of red blood cells.
The ranges
| Category | B12 (pg/mL) |
|---|---|
| Deficiency | Below 200 |
| Borderline | 200 – 300 |
| Normal | Above 300 |
Ranges vary slightly between laboratories, so always read the range printed on your own report.
Some people have symptoms while sitting in the borderline band. Doctors weigh the symptoms as heavily as the number in that situation.
Who should be tested
- A fully vegetarian or vegan diet
- Tingling or numbness in the hands and feet
- Long-standing tiredness and weakness
- Previous stomach or bowel surgery
- Long-term use of acidity medication
- Older age, particularly past 60
Preparation
Fasting is usually not required, though some laboratories prefer a morning sample. What matters most: if you are taking B12 supplements or injections, tell both your doctor and the laboratory — the result can look normal while the underlying picture is not.
Symptoms with a normal result?
That happens. Doctors may then order further tests, or look for another cause of the symptoms. Nothing is decided from a single number.
Frequently asked questions
Do I need to fast for the B12 test?+
Usually not, though some laboratories prefer a morning sample.
What happens if I am already taking supplements?+
The result can look normal while the underlying picture is not, so tell the laboratory and your doctor.
My result is normal but I still have tingling. What now?+
That can happen. Doctors may order further tests or look for another cause.
How often should vegetarians be tested?+
It depends on your diet and symptoms — ask your doctor to set the interval.