OneDayTests Vitamin B12 (Active and Total) Blood Test
Type
Blood Testing
Biomarkers
2
Duration
30 min
Results
4 days
This test is used to diagnose vitamin B12 deficiency.
This test is used to diagnose vitamin B12 deficiency, which can lead to symptoms such as fatigue, weakness, neurological problems, and megaloblastic anemia. It measures both active and total levels of Vitamin B12. Total B12 refers to all forms of vitamin B12 in the blood, including active and inactive forms. Active B12, or cobalamin, are the biologically active forms immediately available for the body to use. Measuring both is important because not all forms are biologically active. This test provides a complete assessment of B12 status.
Key Details
Who Is This For?
Vegetarians and vegans (at higher risk of B12, iron, and zinc deficiency). Older adults, as nutrient absorption decreases with age. Anyone on restrictive diets or with digestive conditions affecting absorption. People experiencing unexplained fatigue, brain fog, poor wound healing, or hair loss. Athletes with high nutrient demands from training.
What's Included
Preparation Required
Fasting for 8–10 hours is recommended for some nutrient tests but not all — check with your provider. Continue taking your regular supplements unless told otherwise (the test measures your steady-state levels). Morning draws are preferred for consistent results.
Biomarkers Tested
2Essential for nerve function, DNA synthesis, and red blood cell formation. B12 deficiency can cause anemia, neuropathy, fatigue, and cognitive impairment. Common in vegans, vegetarians, older adults, and those taking metformin or acid-reducing medications.
Essential for DNA synthesis, cell division, and red blood cell formation. Folate deficiency causes megaloblastic anemia and, during pregnancy, increases the risk of neural tube defects. Works closely with vitamin B12.
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- Category
- Diagnostic
- Sample Type
- Blood draw
- Duration
- 30 min
- Results
- 4 days
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