Vitamin B12 – Advanced Testing.

Vitamin B12 Advanced Testing Profile from Blue Horizon Medicals

We believe this profile is a little gem – so much information about red blood cell health – and more – can be gathered from the tests within. And very few profiles offer Active B12 levels as standard –with this knowledge you can be far more confident of your true B12 status than you might be with the total B12 level alone…

We offer this as a Hospital visit or alternatively a finger prick kit or a vacutainer kit.

1. Vitamin B12
2. Active Vitamin B12
3. Folate
4. Haemoglobin
5. MCV


is the pigment found in the red blood cell, which gives blood its distinctive colour. Its essential role though is to transport oxygen to the all body’s tissues and organs.

Sometimes too much haemoglobin is made, resulting in polycythaemia – a condition in which too many red blood cells are produced. Causes of polycythaemia include smoking and living at altitude, as well as a genetic tendency to manufacture too many red blood cells in the bone marrow. Dehydration can cause the blood to become more concentrated – which will give the impression of an increased amount of haemoglobin, rather than pointing to a true rise in the level of this protein.

A low haemoglobin level is diagnostic of anaemia – a state of poor quality and deficient red blood cells – the cause of which may be explained by further findings in this set of results – or upon further testing. The size of the red blood cell is a useful guide – see below – and the level of the B vitamins, B12 and Folate, will help guide towards a diagnosis of the underlying cause.


The Mean Cell Volume measurement (MCV) is a useful guide to the size of the average blood cell – from this single measurement a number of investigative paths may open up. The most commonly encountered reasons for a high MCV (implying the red blood cells are enlarged) are Vitamin B12 deficiency, Folate deficiency and alcohol intake at a higher than desired level.

A low MCV is highly suggestive of microcytosis (small red blood cells). Iron deficiency is the most common explanation for a low MCV – but other causes include inherited red blood cell disorders such as thalassaemia and so called ‘anaemia of chronic disease’. An additional ferritin test (or more formal iron studies) would give a good idea of the level of iron stores present, and help to distinguish between an iron deficient state or another cause of a low MCV.

Vitamin B12

Vitamin B12 is a water soluble vitamin which plays an essential role in maintaining normal cell function – most noticeably though in red blood cell activity and in nerve function. Interestingly, complex organisms (animals, plants and fungi) cannot make B12. The vitamin has to be extracted from the diet, and is manufactured only by some species of bacteria.

A high level of Vitamin B12 is not likely to represent significant overdose, as B12 is well tolerated by the great majority of people – even in very high concentrations (as indeed are most water soluble vitamins). Excess levels are usually a result of supplementation or from following a diet rich in the vitamin. A few exceptions to this rule include those who suffer from a rare hereditary eye complaint known as Leber’s disease. Too much vitamin B12 in these individuals can lead to damage of the optic nerve, which might lead to blindness. Anyone who is allergic to cobalt should also avoid taking vitamin B12 – as the vitamin contains a significant amount of this element. Rarely, high dose supplements or injections of Vitamin B12 cause diarrhoea, itching, blood clotting and allergic reactions. Liver disease and myeloproliferative disease (disorder of the bone marrow) can lead to elevated levels of B12. However, individuals who are vulnerable to high doses of B12 in practice are few and far between. Indeed, some practitioners advocate high doses of Vitamin B12 to help sufferers from Chronic Fatigue Syndrome (CFS) and to combat the development of Alzheimer’s disease, amongst other conditions.

Characteristically, in Vitamin B12 deficiency the red blood cells are enlarged (if the deficiency is severe and longstanding), leading to a rise in the MCV. The threshold for diagnosing vitamin B12 deficiency is a matter for debate. Some experts believe levels of 400-500 pmol/L are desirable and that levels below this may lead to symptoms. A level which is sustained below 140 pmol/L will ultimately result in megaloblastic anaemia (or Pernicious Anaemia (PA)), in which there is reduced quality and number of red blood cells. Deficiency may be the result of either low intake of the vitamin or from impaired absorption from the gut. Poor absorption owing to a deficiency of Intrinsic Factor (IF) is generally the underlying reason for PA – and usually this is caused by an autoimmune action, in which antibodies (manufactured by the body’s immune system) mistakenly attack and destroy IF. Vitamin B12 deficiency in the longer run can lead to nervous system disorders – with sensation changes, loss of power or co-ordination, gut disorders and (rarely) dementia or mental illness. Lower level deficiency has been associated with a range of symptoms such as fatigue, memory impairment, irritability, depression and personality changes.

Active Vitamin B12

As implied by the name, Active B12 is the form of B12 that actually has an effect in the body. When B12 is absorbed from the diet, it is transported in the blood to the cells in two different forms – bound to either haptocorrin (70-90%) or transcobalamin (10-30%). Only B12 which is bound to transcobalamin is ‘available’ however – this is the ‘active’ form.

Many now believe that knowledge of the Active B12 level is more helpful than knowing the total B12 level when evaluating whether or not there is a true deficiency of the vitamin. Total levels may appear within acceptable limits, but as much of it is bound to haptocorin and effectively inert it will be of little use to the body – and symptoms and signs of deficiency may be evident despite the apparently normal level of B12.


Folate (folic acid) is one of the B group of vitamins, found in green vegetables in particular. The body’s reserves of folate, unlike vitamin B12, are low and only sufficient for about four months.

Having a high level of Folate is not likely to cause any difficulty – as a water soluble vitamin, it is usually well tolerated by humans even in high concentrations. Supplementation, or following a diet rich in the vitamin (for example fresh green vegetables), is the usual reason behind a high level of folate in the blood. Excess folate in the presence of low Vitamin B12 levels can lead to problems however – the B12 deficiency is effectively masked by the action of folate which will apparently resolve the megaloblastic anaemia caused by deficiency of either vitamin, but will not resolve the effects of B12 lack. It is important therefore to ensure that the Vitamin B12 level is acceptable if a high Folate level is detected.

Causes of Folate deficiency include reduced intake from the diet or from poor absorption through the gut; increased demand (eg pregnancy) and from the side effects of some medication (eg methotrexate). Symptoms include fatigue, mild sensation changes and depression. Prolonged lack of folate results in megaloblastic anaemia (similar in appearance to that caused by B12 deficiency – large immature red blood cells dominate, giving rise to a high MCV).

Call the team at Blue Horizon Medicals on 0800 999 1110 or you can order the test online!

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