Holotranscobalamin (holoTC), also known as active vitamin B12, is a form of vitamin B12 that is bound to transcobalamin, a transport protein in the blood. This combination is biologically significant because it is the only form of vitamin B12 that can be taken up by cells via receptor-mediated endocytosis, making it readily available for cellular processes. Measurement of holotranscobalamin levels is considered a more direct marker of the recent vitamin B12 status in the body than the total vitamin B12 test, as it represents the fraction of vitamin B12 that is actually available for cellular uptake and immediate use....


Who would benefit from testing their holotranscobalamin levels?

Individuals who are at risk of vitamin B12 deficiency, such as vegetarians, elderly people, and those with absorption impairments like pernicious anemia or gastrointestinal disorders, would benefit from testing their holotranscobalamin levels. It helps in early detection and management of deficiency.

What are symptoms of low holotranscobalamin?

Symptoms of low holotranscobalamin, indicating vitamin B12 deficiency, include fatigue, weakness, memory loss, neurological and psychiatric problems, and anemia. These symptoms result from the impaired production of DNA and red blood cells and neurological function.

How does holotranscobalamin differ from total vitamin B12 testing?

Holotranscobalamin testing measures only the biologically active portion of vitamin B12 available for cellular uptake, providing a more accurate reflection of functional vitamin B12 status. In contrast, total vitamin B12 testing measures all forms of B12, including those that are not immediately available to cells, which can sometimes mask deficiencies.

What causes low holotranscobalamin levels?

Low holotranscobalamin levels are primarily caused by dietary inadequacy, malabsorption syndromes, pernicious anemia, certain medications, and age-related decline in absorption. These factors lead to insufficient availability of biologically active vitamin B12.

Test(s) that measure/test for Holotranscobalamin

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