Empeiria

Cobalamin

Also known as B12, vitamin B-12, cobalamin

compound family · no single molecular formula

LOINC 2132-9 code verified serum pg/mL

unverified These explanations are written to be easy to read and have not yet been checked against a source. The ranges and measurement notes on this page show theirs.

definition unverified

A vitamin you can only get from food, needed to build red blood cells and to keep the insulating layer around your nerves intact.

A vitamin you can only get from food, needed to build red blood cells and to keep the insulating layer around your nerves intact.

No clinical version written yet.

why measured unverified

Shortage is common, easy to correct, and causes nerve damage that does not fully reverse if it is left too long.

Shortage is common, easy to correct, and causes nerve damage that does not fully reverse if it is left too long.

No clinical version written yet.

if low unverified

Your body is running short. There are a few common reasons. A diet with little or no animal food. A stomach that no longer makes the carrier protein B12 needs. Long-term use of acid-reducing or diabetes medicine. Or a gut condition affecting the last part of the small intestine.

Your body is running short. There are a few common reasons. A diet with little or no animal food. A stomach that no longer makes the carrier protein B12 needs. Long-term use of acid-reducing or diabetes medicine. Or a gut condition affecting the last part of the small intestine.

No clinical version written yet.

caveats unverified

Blood levels track stores poorly, and symptoms can appear while the number still looks acceptable. Nerve symptoms with a borderline result are usually worth acting on rather than dismissing.

Blood levels track stores poorly, and symptoms can appear while the number still looks acceptable. Nerve symptoms with a borderline result are usually worth acting on rather than dismissing.

No clinical version written yet.

What this substance is

Vitamin B12 is a family of cobalamins that share a cobalt-centred ring and differ in the group attached to the cobalt. Blood contains several at once and the test measures them together, so no single one is "the" structure.
Methylcobalamin, a principal form in blood. No 3D model: none can be checked. RDKit cannot recompute a cobalt complex's InChIKey, PubChem has no 3D, and the PDB's entry (COB) is a different protonation state that also omits cobalt's bond to its lower ligand.
Adenosylcobalamin (cobamamide), the main form inside cells. No 3D model: none can be checked. No PDB dictionary entry exists, PubChem has no 3D, and RDKit cannot generate or verify it.
n=1: 2n=2: 8n=3: 1427 p⁺32 nCo³⁺24 electrons · not to scale
Co3+: the cobalt at the centre of every cobalamin, shown as the isolated ion. Inside cobalamin its bonds rearrange its 3d electrons, and the free ion's cloud is not spherical (ground term 5D), so 2D only

Each molecule is drawn from ChEBI's curated 2D drawing, accepted only after its InChIKey, formula and charge matched the ChEBI release. Atom diagrams are checked against the NIST Atomic Spectra Database.

3D model · cobalt(3+)

A schematic atom: a nucleus of 27 protons and 32 neutrons (the most common isotope, 59Co), inside its electron shells, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶. The configuration matches the NIST Atomic Spectra Database ground state of Co IV (5D<4>). That term is not an S state, so the cloud is not spherical: the filled subshells are drawn as spherical clouds, and the partly filled 3d⁶ subshell as the shapes of its 5 orbitals, which its 6 electrons share. Not to scale: shells are spaced on a square-root scale so the inner ones stay visible, and the nucleus is magnified about ten-thousand-fold.

Reference ranges

Checking your own result against this range needs the running application; this is a static copy. Nothing you type anywhere in Empeiria is ever sent to a server.

This open edition shows a range only where a public-domain or openly licensed source states one, and none does for this marker yet. Compare your result with the range printed on your own lab report.

How it is measured

In practice

A health worker takes a small amount of blood from a vein in your arm with a needle. You should not eat or drink for about 6 to 8 hours before the test. Some medicines can change the result, so ask your provider before the test.

Venous blood sample. Fast for about 6-8 hours beforehand. Drugs that can affect the result include colchicine, H2 receptor blockers, metformin, neomycin, para- aminosalicylic acid, phenytoin and proton pump inhibitors; the provider decides whether any should be stopped.

Before the test

  • Do not eat or drink for about 6 to 8 hours before the test.
  • Do not stop any medicine before talking to your provider.

Where: laboratory

Sources: Vitamin B Test, MedlinePlus (U.S. National Library of Medicine); Vitamin B12 level, MedlinePlus Medical Encyclopedia cited · not yet checked by a person

In the lab

immunoassay

Competitive intrinsic-factor binding assay

First the test frees B12 from the proteins that carry it. Then the B12 from your blood competes with a tagged B12 for a protein that grabs B12. Less tagged B12 caught means more B12 in your blood.

After a pretreatment step releases B12 from its binding proteins, sample B12 and a labelled B12 compete for intrinsic factor, the B12-specific binding protein used as the assay's binder; the measured signal falls as the sample's B12 rises. Automated platforms such as the Roche Elecsys read the signal by electrochemiluminescence.

  • Read by: Electrochemiluminescent signal (e.g. Roche Elecsys ECLIA); falls as sample B12 rises

What can throw it off

  • anti-intrinsic-factor antibodies
  • rheumatoid factor
  • heterophile antibodies
  • vitamin B12 macrocomplexes (macro-B12)
Why labs disagree: Different B12 assays give different numbers on the same samples: when NHANES changed from the Bio-Rad radioassay to the Roche immunoassay, a crossover study of the same specimens found the Roche values were higher (median 593 vs 529 pg/mL). Antibody-mediated interferences (including anti-intrinsic-factor antibodies and macro-B12) can also distort individual results.

Sources: Interference by vitamin B12-macrocomplexes: towards an effective detection and correct interpretation of hypo- and hypervitaminemia (Clin Chem Lab Med, PMC open access); NHANES 2011-2012: Vitamin B12 Data Documentation, Codebook, and Frequencies (CDC/NCHS) cited · not yet checked by a person

What it reports on

Associated symptoms

When low

Conditions this marker features in

When low
  • low Low vitamin B12 · defining
    Below 148 pmol/L is commonly taken as clear deficiency, and 148-220 (or 260) pmol/L as mild; but 30-40% of people with symptoms have a normal level.
  • low Low white blood cell count · supportive
    Low vitamin B12 is an uncommon cause of a low white count (under 2% in one study). B12 was part of the workup.

Ordered as part of

vitamins