Vitamin B12: “Normal” blood Levels are often not normal

A new study published in the Annals of Neurology by researchers at UCSF challenges our current understanding of what constitutes “normal” vitamin B12 levels, particularly regarding brain health. The findings suggest that even B12 levels currently considered adequate may not be optimal for maintaining brain function, especially in older adults.

Key Findings

The study examined 231 healthy older adults with B12 levels that would typically be considered normal. Surprisingly, those with lower B12 levels – though still within the “normal” range – showed several concerning signs:

Slower nerve conduction in visual pathways

Reduced cognitive processing speed, particularly in older participants

More white matter damage visible on brain MRI scans1

Why This Matters

The current normal levels for vitamin B12 were determined decades ago, and it is not clear how reliable the research that led to these values was. Quest and Labcorp, two major chains of laboratories, define normal levels as 200 – 1,000 pg/ml and 232 -1,245 pg/ml, respectively. The WHO considers 480 pg/ml to be the bottom of the normal range, while it is 500 pg/ml in Japan. Some experts suggest these higher standards may contribute to lower rates of Alzheimer’s and dementia in Japan.

What This Means for You

Your B12 levels might be worth checking if you are experiencing neurological symptoms like:

Mental fogginess

Memory issues

Balance problems

Numbness or tingling

Migraine headaches, especially with visual auras

Dizziness

If you have this blood test done, don’t accept “it’s normal” from your doctor, but ask about your actual level.

 Why are so many people deficient

Ironically, a healthy diet is low in vitamin B12. Vegetarians are at a greater risk of becoming deficient. Another common factor is antacid medications such as omeprazole (Prilosec), pantoprazole (Protonix), esomeprazole (Nexium), and others. Genetic factors also play a role.

 Special Considerations for Older Adults

The study found that older adults may be particularly vulnerable to the effects of lower B12 levels. This is especially important because:

B12 absorption tends to decrease with age

The impact of lower B12 on cognitive processing speed was more pronounced in older participants.