Description
Overview: Vitamin B12 circulating in the blood is attached to different proteins. Only a small fraction (about 10-30%) is attached to a protein called transcobalamin, forming “Active B12” (or holotranscobalamin). This is the only form that can be delivered into your cells for use. The standard “Total B12” test measures both active and inactive forms.
Clinical Significance: Measuring Active B12 gives a truer picture of your B12 status.
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Early Detection: It is often the first marker to fall when B12 stores are becoming depleted, allowing for earlier diagnosis of deficiency before severe symptoms develop.
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Greater Accuracy: It helps clarify “borderline” results from a standard Total B12 test. A normal Total B12 but low Active B12 indicates a functional deficiency.
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Deficiency Symptoms: B12 is crucial for nerve function and red blood cell production. Deficiency can cause fatigue, anemia, nerve damage (tingling/numbness in hands and feet), and cognitive issues (memory loss, brain fog).
When is this test recommended?
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When a patient has symptoms of B12 deficiency (fatigue, neurological issues) but their standard Total B12 test result is borderline or low-normal.
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To screen high-risk groups, such as vegans/vegetarians, the elderly, and individuals with digestive disorders that affect nutrient absorption (e.g., Crohn’s disease, celiac disease).
Sample Requirements:
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Specimen: Serum.
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Container: Gold Top (SST) or Red Top Tube.
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Preparation: No fasting is typically required.
