Vitamin B12

Vitamin B12 testing measures blood levels of this vitamin (cobalamin). It is performed for fatigue, anaemia, tingling in hands and feet or memory problems, and in people at higher risk of deficiency, such as vegans, older people and those taking metformin or acid-reducing medicines long term.

Who is this test for

• people with persistent fatigue, weakness or pallor, and those with anaemia;
• people with tingling or numbness in hands and feet, unsteady walking or memory problems;
• vegans and people eating few animal-source foods, particularly during pregnancy and breastfeeding;
• older people;
• people taking metformin or acid-reducing medicines for a long time;
• people with pernicious anaemia, Crohn’s disease or coeliac disease and after certain stomach or bowel operations;
• people using nitrous oxide (“laughing gas”) recreationally.

What vitamin B12 is and why it matters

Vitamin B12 is needed for red blood cell formation, DNA synthesis and nervous system health, where it helps form the myelin sheath of nerves. In many processes, it works together with folic acid.

Vitamin B12 is produced by bacteria; people obtain it almost exclusively from animal-source foods: meat, offal, fish, seafood, milk, dairy and eggs, as well as fortified foods and supplements. Intestinal absorption requires intrinsic factor, a protein made by the stomach.

The liver stores enough vitamin B12 for several years. Deficiency due to inadequate intake therefore develops gradually, and symptoms usually appear only after several years.

Older people more often have atrophic gastritis and poorer absorption from food. Pernicious anaemia is an autoimmune disease in which the stomach does not produce enough intrinsic factor. Higher-risk groups also include people after stomach surgery, bariatric surgery or removal of the terminal small intestine, and those taking proton pump inhibitors such as pantoprazole and omeprazole, or H2 blockers, for a long time.

Symptoms of vitamin B12 deficiency

Deficiency may cause fatigue, weakness, pallor, breathlessness on exertion and an inflamed, sore tongue. The blood count may show anaemia with enlarged red cells (macrocytic anaemia), so B12 is often tested alongside complete blood count.

Neurological symptoms are also common: tingling, numbness or burning in feet and hands, unsteady walking, memory and concentration problems, and mood changes such as depression. They may occur without anaemia. Long-term deficiency may cause dementia-like cognitive problems but is not a cause of Alzheimer’s disease. Detecting and treating deficiency promptly matters because longstanding nerve damage may not resolve completely.

Save with a panel

Test B12 is also included in these panels.

Healthy hair, skin and nails panelVitamin B12, zinc, Vitamin D, folic acid, iron and 3Price of individual tests: 145.80€121.00€Details ›Energy balance panelvitamin D, vitamin B12, folic acid, calcium, magnesium and 498.50€Details ›

All panels including B12 (8) ›

Preparation and sample

A venous blood sample is taken. Fasting is not essential for this test alone, but if glucose, lipids or PT are measured from the same collection, come fasting in the morning. If possible, sample before starting vitamin B12 replacement.

If you already take B12 supplements or receive injections, tell staff at blood collection and your doctor, because results then reflect replacement rather than just your stores. If you take biotin (e.g. hair and nail supplements), mention this at blood collection.

How results are interpreted

Vitamin B12 is expressed in pmol/L; the reference interval depends on method and is printed on the report. A doctor interprets it alongside symptoms, blood count and medicines.

Low B12 with appropriate symptoms suggests deficiency. Values near the lower limit fall in a “grey zone” where deficiency is neither confirmed nor excluded. British NICE guidelines from 2024 state as a guide that deficiency is likely when total B12 is below 133 pmol/L, while 133 to 258 pmol/L is considered indeterminate.

For an indeterminate result, a doctor may measure, alongside blood count, homocysteine or other tests; with confirmed deficiency, the cause is investigated, such as pernicious anaemia or poor absorption.

How to arrange testing

You can come for blood collection without an appointment or referral at one of our branches throughout Croatia (listed on the Contactpage). Prices for all tests and panels are listed in the service price list. Vitamin B12 is often measured together with folic acid and a complete blood count.

Frequently asked questions

What does low vitamin B12 mean?

Low B12 means the body probably lacks this vitamin because of diet, poor absorption or medicines. A doctor assesses symptoms and blood count alongside the result, looks for a cause and prescribes tablet or injection replacement.

Can I be B12-deficient despite normal results?

This can happen, particularly near the lower limit or after recent B12 supplement use. If symptoms suggest deficiency, a doctor may recommend additional tests such as homocysteine.

What does high vitamin B12 mean?

High B12 most often results from supplements or injections. If you do not use them, a doctor assesses whether further investigation is needed because high B12 may also accompany liver or blood disease.

Should vegans check vitamin B12?

Vegans and people eating very few animal-source foods need B12 from fortified foods or supplements. Testing is useful with symptoms, during pregnancy and breastfeeding, and when adequate intake is uncertain.