Active vitamin B12
Vitamin B12 is particularly necessary for the formation of red blood cells and, together with folic acid, DNA. It also supports the functioning of the brain and nervous system, and it is involved in carbohydrate and protein metabolism.
We get vitamin B12 from products of animal origin, such as liver, fish, eggs, meat, and dairy products. Stomach cells produce a carrier protein called intrinsic factor (IF), to which vitamin B12 binds and with which it is absorbed in the small intestine. From the small intestine, vitamin B12 continues its journey through the bloodstream to the tissues, again bound to the carrier protein.
The vitamin B12 blood test indicates the total concentration of vitamin B12 in the body. A vitamin B12 sufficiency in the body, however, is more accurately indicated by the test of active vitamin B12 (S-B12-TC2). The abbreviation “TC” refers to the transcobalamin in the vitamin B12 carrier protein.
Vitamin B12 deficiency is primarily a concern of the elderly. One in ten Finns aged over 65 have been found to suffer from vitamin B12 deficiency. It is less common among younger people. Vitamin B12 deficiency is easier to prevent than treat.
When is a good time to measure vitamin B12 levels?
Often, the need to examine the concentration of vitamin B12 arises in connection with the nervous system or anaemia with elevated red blood cell volume (E-MCV).
It is a good time to have the test done if you experience the following symptoms, which are possibly caused by vitamin B12 deficiency:
- Muscle weakness
- Sensory disturbances
- Memory disturbances
- Pain in the upper abdomen
- Disorientation, memory loss
- Dizziness, fatigue, weakness
- Fast heart rate
- Shortness of breath
Less common symptoms include:
- Tongue infection
- Weight loss
- Yellowness of the skin
What does a vitamin B12 test measure?
The body stores vitamin B12 in the liver for approximately 3–5 years, so it can take months, even years, before the symptoms suggesting vitamin B12 deficiency occur. On the other hand, children have not yet developed a stock of vitamin B12, so vitamin B12 deficiency manifests itself earlier.
How to interpret the vitamin B12 test result?
Normally, the result is:
Please contact your physician or other healthcare professional if you suspect an illness or need help interpreting the results.
Read more about defining reference values.
What can cause elevated vitamin B12 values?
People who have received vitamin B12 treatment have been found to have elevated levels of vitamin B12. If the excessive intake of vitamin B12 is caused by vitamin supplements, this is not dangerous. Therefore, you should have the blood test taken before receiving the vitamin B12 treatment dose. Elevated vitamin B12 levels can also be caused by liver and kidney diseases or a malignant tumour.
What can cause decreased vitamin B12 values?
Usually, vitamin B12 deficiency is caused by absorption problems. Decreased gastric acid concentration and an increase in stomach pH weaken the absorption of vitamin B12. Gastric acidity can be decreased by an autoimmune disease or a helicobacteria-induced stomach infection, or gastritis. Some medications, such as antacids and the diabetes drug metformin, as well as diseases of the small intestine (coeliac disease), can weaken the absorption of vitamin B12.
Low vitamin B12 levels can also be caused by diet. Vitamin B12 only exists in high concentrations in products of animal origin, and if a person following a vegan diet does not take it as a supplement, its concentration in the blood decreases.
The secretion of vitamin B12 from the kidneys increases in connection with high alcohol consumption.
Decreased vitamin B12 levels can also occur among those following a vegetarian diet. Vitamin B12 deficiency causes anaemia and nervous symptoms, and the blood platelet and white blood cell counts are lower than normal. It is typical of anaemia caused by vitamin B12 deficiency that the red blood cells are unusually large. This type of anaemia is known as megaloblastic anaemia.
The most typical additional vitamin B12 tests:
- Complete blood count (CBC), shows the number of red and white blood cells, number of platelets, and cell type (3696 B-TVK)
- Homocysteine is connected to clotting events and blood clots (1867 P-Hcyst)
- Folic acid has effects on the well-being of the brain and cells (1416 fS-Folaat)
Sources (Vitamin B12):
SYNLAB test list: https://www2.synlab.fi/laboratoriokasikirja/tutkimuskuvaukset/b12-vitamiini-aktiivinen-transkobalamiini-ii-een-sitoutunut-1142-s-b12-tc2/
SYNLAB vitamin B12 https://www.yml.fi/tuotekuvaus_show.php?tuotenro=43
Terveyskirjasto health library: B12-vitamiinin tai foolihapon puutos https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=dlk00788&p_hakusana=b12
Terveyskirjasto health library: B12-vitamiini, transkobalamiini II:een situoutunut (S-B12-TC2) https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=snk99003&p_hakusana=b12
Terveyskirjasto health library: B12-vitamiini (S-B12-Vit) https://www.terveyskirjasto.fi/dlk01300/vitamiinit?q=B-vitamiini#s10
Lab tests online: Vitamin B12 and folate deficiency https://labtestsonline.org.uk/conditions/vitamin-b12-and-folate-deficiency
Fasting is not required
This examination does not require fasting