LIVE: B12

Vitamin B12 - why it matters (especially in midlife)

Vitamin B12 plays a key role in:

• Brain and nervous system function

• Energy levels and fatigue

• Red blood cell production

• DNA synthesis and cell repair

• Healthy pregnancy and fetal brain development

Low or borderline B12 can contribute to fatigue, brain fog, low mood, memory or concentration issues, pins and needles, balance problems, and anaemia. Importantly, neurological symptoms can occur even without anaemia.

In my clinical practice, many people report feeling better with B12 levels in the mid-to-upper reference range, rather than simply “within normal limits”.

What is “low” B12?

There is no single cut-off that applies to everyone.

• B12 levels fluctuate

• Symptoms can occur at “low–normal” levels

• Lab reference ranges do not always reflect functional sufficiency

As a general guide:

• <150 pmol/L → deficient

• 150–300 pmol/L → often sub-optimal

• >300 pmol/L → usually adequate

From a preventative medicine perspective, many clinicians aim for levels around ≥400 pmol/L, particularly in people with symptoms or risk factors.

This approach is informed by geriatric medicine, where B12 supplementation is commonly used to support recovery and neurological resilience in older hospitalised patients - prompting the question: why wait until illness to optimise B12?

Why B12 deficiency is common

Even with a reasonable diet, B12 deficiency is common due to:

• Reduced absorption with age

• Lower stomach acid and intrinsic factor

• Medications (e.g. metformin, PPIs, H2 blockers)

• Gut conditions or surgery

• Vegetarian or vegan diets

Supplementation (brief overview)

• Oral B12 is effective for most people and widely used

• Typical doses range from 50–150 mcg daily for maintenance

• Higher doses (e.g. 1000 mcg daily) may be used when levels are low

• Injections are reserved for severe deficiency or proven malabsorption

Levels are usually rechecked after 3–6 months.

References

Andrès E et al. Vitamin B12 deficiency in elderly patients. CMAJ, 2004

O’Leary F, Samman S. Vitamin B12 in health and disease. Nutrients, 2010

Hunt A, Harrington D, Robinson S. Vitamin B12 deficiency. BMJ, 2014