Doctor's Assessment Included
Every result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
Active Vitamin B12
Active Vitamin B12 measures the bioavailable B12 your cells can utilise. For athletes, B12 may support oxygen transport, energy metabolism, and recovery. This test could help optimise your performance-related nutritional status.
Reference Ranges
Low
35
Normal
108
High
Low
35
Normal
108
High
Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.
What It Measures
This test measures holotranscobalamin, the active fraction of vitamin B12 bound to transcobalamin II. This is the only form of B12 that can be taken up by all cells in your body for essential metabolic processes.
Why It Matters
Athletes may have higher B12 demands due to increased metabolic activity. Low active B12 could be associated with reduced endurance, slower recovery, and impaired red blood cell production. Consider discussing your levels with a sports medicine provider.
When to Test
Testing may be recommended if you follow a vegetarian or vegan diet, experience unexplained fatigue or tingling in your extremities, are over 50, or have digestive conditions that could affect nutrient absorption. Consult your healthcare provider for guidance.
Symptoms
Low Levels
Some people with low active B12 levels may experience fatigue, weakness, tingling or numbness in hands and feet, difficulty concentrating, mood changes, and pale skin. A healthcare provider should evaluate persistent symptoms.
High Levels
Elevated active B12 levels are less commonly associated with symptoms but may sometimes indicate underlying conditions such as liver disease or certain blood disorders. Your healthcare provider can help interpret high results in context.
Lifestyle Tips
Including B12-rich foods such as meat, fish, eggs, and dairy in your diet may help support healthy levels. Those on plant-based diets might consider discussing supplementation with their healthcare provider. Regular monitoring can help track your status over time.
Frequently Asked Questions
What is the difference between active B12 and total B12?
Active B12 measures only the form your cells can use, while total B12 includes both active and inactive forms. Active B12 is generally considered a more reliable early indicator of deficiency by many healthcare professionals.
Who may be at risk for low active B12?
People following vegan or vegetarian diets, older adults, those with digestive conditions like Crohn's disease or celiac disease, and individuals taking certain medications such as metformin or proton pump inhibitors may have an increased risk.
How often should I test my active B12 levels?
Testing frequency depends on your individual circumstances. Your healthcare provider can recommend an appropriate schedule based on your diet, medical history, and any symptoms you may be experiencing.