Know your test: Vitamin B12

Dr David Howdijam *

A vitamin B12 level test measures the amount of B12 in the blood. B12 is an important vitamin for many basic bodily functions, such as brain health, blood cell production, and proper nerve functioning. Low B12 levels can lead to serious nerve damage and deteriorating brain functions.

The test is also done for new mothers who breastfeed to monitor their vitamin B12 levels. Deficiency of this vitamin in the mother puts children at a greater risk for neurological damage and developmental problems.

The test is fairly simple – it just requires getting a blood sample. It only takes a few minutes, but can provide extremely valuable information about the presence or absence of this critical vitamin in the body.

Why is the test performed?

A doctor might recommend a B12 test if one has symptoms, such as:

Tingling in the hands and feet; a problem with balance; a racing heart; confusion; dementia; weakness and loss of appetite.

B12 is also done if the doctor suspects pernicious anaemia/megaloblastic anaemia. There is a reduction in red blood cells that occurs when one’s intestines are not able to absorb vitamin B12 or when there is a dietary deficiency. Symptoms of this condition include diarrhoea or constipation, exhaustion, loss of appetite, pale skin, and inflamed red tongue or gums that bleed.

Who might need a vitamin B12 test?

One’s risk for a B12 deficiency is much higher if one eats a vegetarian diet. This is because most food sources of vitamin B12 come from animal products, such as: Diary; eggs; fish and meat.

Vegetarians and those who have specific medical conditions that affect the absorption of B12 in the body might need a B12 test.

One may also need a vitamin B12 test if one is on medications to treat diabetes or acid reflux, as some of these can interfere with healthy B12 levels.

How is the test performed?

A blood sample is needed.

Preparation for the test :

One should not eat or drink for about 8 to 10 hours before the test. One should make sure that he or she is well hydrated on days leading up to the test. It is also important to tell the doctor about any medications as certain drugs may interfere with the test results.

Results of a vitamin B12 test :

Both high and low levels of vitamin B12 may be a problem. High levels of B12 may be present in people who have liver disease, certain types of leukaemia, and diabetes. If one is obese or eat a lot of meat, the B12 levels may also be high.

Low levels of B12 may suggest: Vitamin B12 deficiency anaemia; an internal parasite; Hyperthyroidism (overactive thyroid) and Folic acid deficiency anaemia.

What affects the test?

Certain factors that affect the results of the test include: Taking certain medications that might affect the results; being pregnant or breast-feeding; taking large doses of vitamin C and drinking large amounts of alcohol.

What to think about :

If a person is deficient in both B12 and folate but only takes folic acid supplements, the B12 deficiency may be masked. The anaemia associated with both may be resolved, but the underlying neuropathy will persist.

Folic acid levels can be high in people who lack vitamin B12. A folic acid is often evaluated at the same time as vitamin B12.

Conclusion :

B12 deficiency is not a bizarre, mysterious disease. B12 deficiency is far more common than most people realise. It is estimated that it affects about 40% of all people over 60 years of age. It is entirely possible that at least some of the symptoms we attribute to “normal” ageing – such as memory loss, cognitive decline, decreased mobility, etc. – are at least in part caused by B12 deficiency.