Vitamin B12 deficiency
A vitamin B12 deficiency means your body has too little B12 for your nerves and your red blood cells. You often notice it as tingling in your hands or feet, poor balance or tiredness, sometimes before your blood count changes. One value in your blood shows where your store stands: vitamin B12. It usually comes down to absorption, not to what you eat.
What are the symptoms of a vitamin B12 deficiency?
- ComplaintEvidence
- Tingling or numbnessstrong
In your hands or feet.
- Poor balancestrong
Movements become less precise.
- A smooth, pale tonguestrong
With a deficiency that has lasted longer.
- Tired and weakstrong
- Forgetfulnessstrong
With a deficiency that has lasted longer.
- Low moodfair
Later, with anaemia
- Looking palestrong
Less colour in your face.
How strong is the evidence?
- strong
- In the Dutch guideline, or confirmed in several controlled trials.
- fair
- From one controlled trial, an international guideline or a review of research.
- limited
- The research does not point one way.
Evidence as of October 2026. New research can shift this.
These complaints are also described with iron deficiency, anaemia, an underactive thyroid, low testosterone.
A slightly lowered B12 often goes without complaints, and complaints can exist at a value that looks normal. Precisely that poor correlation is why the grey zone is worked out with methylmalonic acid instead of guessed away.
None of these complaints belongs to a vitamin B12 deficiency alone, and a measurement explains no complaint: the reading and the diagnosis belong with your GP. The complaint list follows the Dutch GP guideline on anaemia (NHG), Thuisarts.nl and research on vitamin B12 deficiency.
How does a B12 deficiency develop?
A B12 deficiency usually develops slowly. Your body has a store, and draws on that first.
- Your store runs downYour vitamin B12 value falls. You often do not notice yet.Your vitamin B12
- Your cells notice the shortageMethylmalonic acid rises: a sign your body is missing B12. Nerve complaints can already start.Your MMA
- Larger red blood cellsYour red blood cells get larger, and then your haemoglobin falls: anaemia.Your MCV
When is your vitamin B12 too low?
The store gauge in your blood. With a grey zone in which the result alone does not say enough.
Normal:
175 to 569 pmol/L
Enter your value as it appears on your results. Range for adults.
No value yet? How to get it measured
How do you replenish a B12 deficiency?
Eat enough B12
Where B12 is
- Meat and fish
- Beef
- Fish
- Dairy
- Milk
- Cheese
- Eggs
If you eat vegan
- A supplementBeside products with added B12.
One tablet a day
B12 injections
See whether your complaints are gone
Keep an extra eye on your B12
The schedule follows Thuisarts.nl, based on the Dutch GP guideline on anaemia (NHG).
What causes a vitamin B12 deficiency?
Absorption
Most common
Absorption
Most common- Pernicious anaemia, in which the immune system disables the uptake factor
- Long-term use of acid-suppressing medication or metformin
- After stomach or bowel surgery
- Declining stomach function at older age
Intake
Intake
- Vegan or largely plant-based eating without a supplement
Consumption and other
Less common
Consumption and other
Less common- Nitrous oxide use, which disables the B12 you already have
- Pregnancy and breastfeeding, in which demand rises
How to get a vitamin B12 deficiency measured
Every value below has its own page: what is normal, and what your value means.
| Value | What it shows | Points here when |
|---|---|---|
| Vitamin B12defining | The store gauge in your blood. With a grey zone in which the result alone does not say enough. | low |
And 5 values that complete the picture
| Value | What it shows | Points here when |
|---|---|---|
| MMA | Accumulates as soon as cells genuinely run short of B12. The decider in the grey zone. | high |
| MCV | The average cell size. In this deficiency red blood cells come out larger. | high |
| RDW | Rises when old and new cells mix, also in a combined deficiency with iron. | high |
| Hemoglobin | Falls late. The nerve complaints can be there before the Hb moves. | low |
Also in this test
- The Iron & fatigue test (€99, single test) measures the values on this page.
- Every draw is fasted: nothing to eat or drink from midnight, only water. Appointments are therefore in the morning, until 12:00.A B12 supplement taken the same day can raise your value.
- You can draw at 600+ locations near you, no referral needed. See the locations
- Results within 24 hours of analysis, in the app.
What is a vitamin B12 deficiency?
Vitamin B12 is needed in two places at once. Fast-dividing cells, such as the precursors of red blood cells, need it to make DNA; without enough B12 the cells become too large and too scarce. And the nerves need it for their insulating layer; there a deficiency gives tingling, numbness and unsteady walking. Those two tracks do not run in step, so the complaint side can run months ahead of the blood count. B12 is only in animal products, and to absorb it the gut needs a protein from the stomach. That is why the most common causes are a stomach that no longer makes that protein, through an autoimmune inflammation or simply through getting older, years of acid suppressants or metformin, a stomach operation or bowel disease, and plant-based eating without fortified products or a supplement. Nitrous oxide makes the B12 you already have inactive in one go. Measuring is harder here than it seems. The liver keeps a store that lasts for years, and total B12 in your blood does not always say how much of it the cells can really use. That is why there is a grey zone in which the number alone does not answer the question, and methylmalonic acid (MMA) decides: it accumulates as soon as cells genuinely run short of B12.
What is a vitamin B12 deficiency confused with?
Each with the one value that tells the two apart.
Folate deficiency
Gives the same blood picture with large red blood cells. That is why folate and B12 are measured together; the nerve complaints belong to B12 alone.
A B12 deficiency is one of the routes into anaemia, but the nerve complaints can run ahead of the blood count. A normal Hb does not rule this deficiency out.
Frequently asked questions
Below 133 pmol/L it is a deficiency wherever you measure. Above that it differs: the lower limit runs from 133 to 175 pmol/L, so the same 150 can be called a deficiency on one report and normal on another. Between 175 and 245 is a grey zone in which the number alone does not answer the question; there methylmalonic acid decides, which rises as soon as the cells genuinely run short.
Sources 9
- 1.NHG-Standaard Anemie. 2024. richtlijnen.nhg.org
- 2.Unilabs test directory, vitamin B12. 2026. bepalingenklapper.nl
- 3.Star-shl test directory, vitamin B12. 2026. star-shl.nl
- 4.Certe test directory, vitamin B12. 2026. bepalingenwijzer.certe.nl
- 5.Clinical Diagnostics test guide, vitamin B12. 2026. clinicaldiagnostics.nl
- 6.Thuisarts.nl (NHG), I may have too little vitamin B12. 2026. thuisarts.nl
- 7.Thuisarts.nl (NHG), I have anaemia. 2024. thuisarts.nl
- 8.Voedingscentrum (Netherlands Nutrition Centre), vitamin B12. 2026. voedingscentrum.nl
- 9.Patel and McGuirk, vitamin B12 deficiency: common questions and answers, American Family Physician. 2025. pubmed.ncbi.nlm.nih.gov
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This page explains what a result means. It is not a diagnosis and not treatment advice. Discuss complaints or an abnormal value with your doctor.
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