Why B12 is Important
Vitamin B12 deficiency can have major implications for health. B12, also known as cobalamin, is a water-soluble vitamin that plays a critical role in several bodily functions. It is essential for red blood cell production, DNA synthesis, and neurological function. B12 deficiency can lead to serious health issues, as B12 supports brain health, energy metabolism, and immune function. Without sufficient levels, the body cannot efficiently transport oxygen, maintain nerve integrity, or produce energy. Since B12 is not synthesized by the human body, it must be obtained from dietary sources or supplementation.
B12 Deficiency
B12 deficiency can have severe health consequences if left untreated. Symptoms and conditions associated with B12 deficiency include:
- Fatigue and weakness
- Memory problems and difficulty concentrating (brain fog)
- Mood disturbances, including depression and irritability
- Neurological issues such as numbness, tingling in the hands and feet, and muscle weakness
- Difficulty walking and balance problems
- Anemia and pale skin
- Shortness of breath and dizziness
- Glossitis (inflamed tongue) and mouth ulcers
- Vision disturbances and optic nerve damage
- Cardiovascular disease risk due to elevated homocysteine levels
- Increased susceptibility to infections due to weakened immune function
Common symptoms include fatigue, weakness, memory problems, and mood disturbances. Since B12 is essential for nerve function, its deficiency can lead to neurological issues such as numbness, tingling in the hands and feet, and even irreversible nerve damage. A prolonged deficiency increases the risk of anemia, cardiovascular disease, and cognitive decline. The elderly, vegetarians, vegans, and individuals with digestive disorders such as Crohn’s disease or pernicious anemia are at higher risk of deficiency.
How to Properly Test B12 Status
Assessing B12 status is crucial, as symptoms of deficiency can overlap with other conditions. Several biomarkers are used to evaluate B12 levels:
Serum B12
This is the most common test, measuring the total B12 in the blood. However, it does not distinguish between active and inactive forms of B12, making it a less sensitive marker. Because the poor sensitivity of this marker it can often not show insufficiency or deficiency in its early stages.
Holotranscobalamin (HoloTC aka Active B12)
This measures the biologically active form of B12 that is readily available for cellular uptake. It is a more reliable indicator of early deficiency compared to total serum B12 and is the preferred marker for B12 status.
Methylmalonic Acid (MMA)
Elevated levels of MMA in the blood or urine indicate functional B12 deficiency. This test is considered highly sensitive since MMA accumulates when B12-dependent metabolic processes are impaired.

For the most accurate assessment, you should get active B12 measured over standard B12 given the sensitivity. If questionable b12 deficiency is still suggestive then getting your MMA checked may provide more information.
The Best Sources of B12
While B12 is ONLY found in animal products such as meat, fish, eggs, and dairy, the most concentrated and bioavailable source is beef organs, particularly liver. Beef liver provides an astonishing 70-80 mcg of B12 per 100 grams, which is approximately 2917-3333% of the Recommended Daily Allowance (RDA). Beef kidney also offers high levels, around 55-60 mcg per 100 grams, equating to 2292-2500% of the RDA, while beef heart contains approximately 8-10 mcg per 100 grams, covering 333-417% of the RDA. In comparison, muscle meat like beef steak provides only about 2-5 mcg per 100 grams, contributing 83-208% of the RDA. Beef organs are also rich in other essential nutrients such as iron, folate, and vitamin A, making them a superfood for overall health. Consuming grass-fed beef liver, either fresh or in desiccated supplement form, ensures optimal B12 intake, especially for individuals at risk of deficiency.
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Conclusion
Vitamin B12 is an indispensable nutrient for energy, brain function, and overall well-being. Deficiency can lead to severe health problems, but proper testing can help diagnose and address it early. For optimal B12 intake, beef organs, particularly liver, remain the best dietary source. Ensuring adequate B12 levels is a simple yet powerful step toward better health and longevity.