Vitamin B12 test
B12 is found almost only in animal products. Your body needs it for red blood cell production and for your nervous system. A deficiency builds slowly, sometimes over years, because your liver holds a substantial store.
What the lab measures is total B12 in your serum. That is a usable measure but not a perfect one: part of the measured B12 is bound to a protein your cells cannot use. A value just above the floor is therefore not automatically read as sufficient.
Folate belongs with it as standard. B12 and folate work in the same pathway, and a shortfall in one can mask the picture of the other. Measuring them separately gives half a conclusion.
Unsure about your B12?
Message what you eat and whether you supplement. With few or no animal products, B12 alongside ferritin is usually the most useful combination.
Reachable Monday to Saturday, 08:00 to 18:00. An appointment can usually be scheduled within a few days.
When to measure this
- If you eat few or no animal products. See the page for vegans and vegetarians.
- If you use acid reducers. Stomach acid is needed to release B12 from food.
- If you use metformin, which lowers absorption over the long term.
- With persistent fatigue or tingling in hands or feet.
- After gastric or bowel surgery, which changes absorption.
What is actually drawn
In the Vitamins and Minerals package these two sit alongside vitamin D, full iron status, magnesium, zinc and calcium.
Preparation
No fasting needed. If you supplement B12, say so in advance. Supplementation often raises the measured value within days, which means the result tells you more about your capsule than your underlying status. To measure the latter, stop for a few weeks in consultation.
Which package includes this
Measuring this marker on its own is possible too. Folate is included regardless, because measuring B12 alone gives an incomplete picture. For reference, providers with a collection point typically charge 59 to 69 euro for a single marker, and you travel there yourself.
These are the actual amounts. The lab cost is what the lab charges, passed on without a markup. There is no discounted-from price and no subscription. Enter your address in the price calculator for the exact total including travel.
What your result means
A value below the reference is a clear signal. Harder is the grey zone just above it, where people with and without symptoms sit together. Symptoms consistent with a deficiency, combined with a value in that zone, is reason to take it to your GP.
What a blood test does not do here: prove your symptoms come from B12. It shows where you stand, which is the information you move forward with.
On the difference between a lab reference and a target range, see this article. If you feel unwell while your value sits inside the reference, read this one.
Frequently asked questions
Why is folate always measured alongside?
Because B12 and folate work in the same pathway.
A shortfall in one can distort the picture of the other. Measuring them together gives a complete picture.
I already supplement B12. Is measuring still useful?
Yes, but the result mostly reflects your supplementation.
Supplementation raises the measured value within days. To know your underlying status, stop for a few weeks in consultation before measuring.
Do I need to fast?
No.
You can eat and drink normally. Only if glucose or triglycerides are drawn from the same tube is fasting required.
My B12 is normal but I still have symptoms. Is that possible?
Yes, that happens.
Part of the measured B12 is bound and unusable by your cells. A value just above the floor does not rule out a functional deficiency. Discuss it with your GP.
Am I more at risk as a vegan?
Yes, B12 is found almost only in animal products.
Without supplementation or fortified products the store depletes over time. See the page for vegans and vegetarians.
Note: a blood test gives you insight and direction. It does not prove or rule out a condition on its own. Results are meant for prevention and for tracking change over time, not as a diagnosis. For symptoms or values outside the reference range, see your GP.