Is Vitamin B12 Testing Worth It?
The hidden deficiency affecting up to 1 in 4 older Australians—often with vague symptoms that mimic ageing. New 2025 research shows neurological changes can occur even when B12 levels appear 'normal.'
52%
of vegans are B12 deficient—and neurological damage can occur even at 'normal' levels
Source: [1]
The Short Answer
Yes—especially for vegans, vegetarians, and those over 60. Vitamin B12 deficiency is surprisingly common and often missed. Research from UCSF in 2025 found that people with B12 levels well within the normal range (averaging 414 pmol/L) still showed neurological changes including slower processing speed and white matter lesions. With 52% of vegans deficient and 20-25% of older Australians affected, testing is valuable—especially since neurological damage may not be fully reversible.[1][2]
The Scope of the Problem
B12 deficiency is more common than most people realise. The data is stark:
52%
of vegans are B12 deficient (<156 pmol/L) compared to just 1% of omnivores[1]
20-25%
of Australians over 60 may be B12 deficient or have suboptimal levels[3]
3-5 years
Your liver stores this much B12—deficiency develops slowly, often too slowly to notice
B12 is unique among vitamins. Your body can store years' worth in the liver, meaning deficiency develops slowly—often too slowly to notice until symptoms become significant. This gradual onset means many people attribute symptoms to 'just getting older' rather than recognising them as deficiency.
'Normal' Isn't Optimal: The 2025 UCSF Finding
Here's where it gets interesting. A landmark 2025 study from UCSF challenged the fundamental assumption that 'normal' B12 levels mean healthy B12 status:
The Key Finding
Older adults with B12 levels averaging 414 pmol/L—well above the deficiency cutoff of 148 pmol/L and firmly within the 'normal' range—still showed measurable signs of neurological and cognitive deficiency:[2]
- Slower processing speed on cognitive tests
- Significant delays responding to visual stimuli
- Higher volume of white matter lesions on MRI scans (lesions associated with cognitive decline, dementia risk, and stroke)
This isn't a borderline finding. It suggests the 'normal' range may be set too low, and many people with technically adequate B12 may still have functional deficiency affecting their brain and nervous system.
This aligns with international evidence: Japan sets its lower B12 limit at 500-550 pmol/L—nearly 4 times higher than many Western laboratories. Some researchers believe the Japanese reference range better reflects truly optimal B12 status, particularly for brain health.[4]
This matters because it shifts the conversation from 'Am I deficient?' to 'Is my B12 level optimal for brain health?'—a very different question.
What B12 Actually Does
Vitamin B12 (cobalamin) isn't just another vitamin—it's essential for fundamental processes throughout your body:
- Nerve function: B12 maintains the protective myelin sheath around nerves. Deficiency causes demyelination—literally stripping the insulation from your nerves. This explains the tingling, numbness, and balance problems.
- DNA synthesis: Required for cell division throughout the body, affecting everything from red blood cells to gut lining to skin regeneration.
- Red blood cell formation: Deficiency leads to megaloblastic anaemia—large, immature red cells that don't carry oxygen effectively. This explains the fatigue and breathlessness.
- Energy metabolism: Converts food into cellular energy via the mitochondrial pathway. Without adequate B12, cellular energy production becomes less efficient.
- Cognitive function: Essential for neurotransmitter production and brain health—hence the white matter changes and cognitive decline seen in the UCSF study.
Symptoms That May Suggest Deficiency
B12 deficiency symptoms often overlap with other conditions or are dismissed as 'normal ageing.' This is precisely why testing can be valuable—it provides objective data when symptoms are vague and non-specific.
Neurological
- Tingling or numbness in hands/feet
- Balance problems, unsteady gait
- Difficulty walking
- Memory problems, cognitive decline
Energy & Mood
- Persistent fatigue
- Weakness
- Depression or mood changes
- Brain fog, difficulty concentrating
Physical
- Pale or yellowish skin
- Sore, red tongue (glossitis)
- Mouth ulcers
- Breathlessness on exertion
Why Early Detection Matters
Neurological damage from prolonged B12 deficiency may not be fully reversible. The myelin sheath can regenerate with treatment, but if demyelination has been severe or prolonged, some damage becomes permanent. This is particularly concerning given the UCSF finding that brain changes occur even at 'normal' levels.[2]
Early detection and treatment offers the best chance of full recovery—another reason why testing before symptoms become severe has real clinical value.
Who Has Higher Risk?
While anyone can develop B12 deficiency, certain groups have significantly elevated risk. If you fit multiple categories, testing becomes more compelling:
| Risk Factor | Why It Matters |
|---|---|
| B12 is only naturally present in animal products. With 52% of vegans deficient, supplementation isn't optional—it's essential. Regular testing confirms adequacy. | |
| Dairy and eggs contain B12, but 50-70% of vegetarians across multiple studies have suboptimal levels. Don't assume you're getting enough. | |
| Any diet limiting animal products increases risk, including many traditional Indian diets and plant-based eating patterns. |
| Risk Factor | Why It Matters |
|---|---|
| Stomach acid decreases with age, reducing B12 absorption from food. This affects 20-25% of older Australians. Supplements bypass this issue and work better. | |
| Autoimmune condition destroying intrinsic factor (required for B12 absorption). Requires lifelong B12 injections—oral supplements don't work. | |
| Bariatric surgery or gastrectomy removes cells producing intrinsic factor. Annual B12 monitoring is standard post-operative care. | |
| Intestinal damage impairs absorption in the terminal ileum where B12 is absorbed. Regular monitoring is recommended. |
| Risk Factor | Why It Matters |
|---|---|
| Used for type 2 diabetes. Reduces B12 absorption—10-30% of long-term metformin users develop deficiency. Some doctors recommend routine supplementation. | |
| Long-term omeprazole, pantoprazole, esomeprazole, etc. reduce stomach acid needed to release B12 from food. Risk increases with duration of use. | |
| Ranitidine and similar medications have the same acid-reducing effect as PPIs, though typically less severe. |
Understanding B12 Test Results
B12 testing sounds straightforward, but interpretation has important nuances that most people—and some doctors—don't fully appreciate:
Generally considered deficient—supplementation typically recommended by all standards
May have functional deficiency despite being 'technically' adequate. Further investigation recommended, especially with symptoms.
Generally considered adequate by conventional Western standards—but see the UCSF caveat below
Japan's lower limit—may better represent optimal B12 status, particularly for brain health
Better Tests: MMA and Homocysteine
Standard serum B12 measures total B12, but only about 20% is in the 'active' form (holotranscobalamin) that cells can actually use. This means serum B12 can appear normal while functional deficiency exists—exactly what the UCSF study demonstrated.
This is where metabolic markers become useful:
When Serum B12 Isn't Enough
Methylmalonic acid (MMA) and homocysteine are metabolic markers that rise when B12 is functionally deficient—even if serum B12 looks normal:[5]
- Elevated MMA + elevated homocysteine: Strong evidence of functional B12 deficiency (98-99% sensitivity when combined)
- Elevated homocysteine only (normal MMA): More likely folate deficiency rather than B12
- Normal MMA + normal homocysteine: Effectively rules out functional B12 deficiency
MMA is more specific for B12 deficiency than homocysteine. If you have symptoms but borderline serum B12 (especially in the 300-500 range), asking your GP about MMA testing can clarify whether you have functional deficiency despite 'adequate' serum levels.
The Folate Trap
High folate intake (common with fortified foods and supplements) can mask the blood changes of B12 deficiency (megaloblastic anaemia) while neurological damage continues silently in the background. Since mandatory folic acid fortification of bread began in Australia in 2009, this interaction has become more clinically relevant.[6]
This is why testing B12 alongside folate is often recommended—especially for those taking folate supplements or consuming lots of fortified breakfast cereals and breads.
What If You're Deficient?
The good news: B12 deficiency is usually straightforward to address once identified. Your GP will recommend an approach based on the severity and underlying cause:
- Dietary deficiency: Oral supplements (typically 1000-2000 μg daily) are highly effective—crystalline B12 in supplements doesn't require intrinsic factor for absorption
- Absorption issues: Higher-dose oral supplements (2000 μg daily) can overcome malabsorption through passive diffusion (about 1% of oral B12 is absorbed passively regardless of intrinsic factor)
- Pernicious anaemia: Usually requires ongoing B12 injections (typically 1000 μg monthly after initial loading doses). Oral B12 won't work regardless of dose.
- Metformin users: Oral supplements typically sufficient; some doctors recommend routine supplementation rather than waiting for deficiency
Response to treatment is often noticeable within weeks for fatigue and mood symptoms, though neurological symptoms may take 3-6 months to improve—or may not fully resolve if damage was prolonged.
The Bottom Line
B12 deficiency is surprisingly common—and 'normal' levels may not mean optimal brain health.
With 52% of vegans deficient, 20-25% of older Australians affected, and 2025 research showing neurological changes even at levels within the 'normal' range, B12 testing is more nuanced than it initially appears.
The UCSF finding is particularly significant: people with B12 levels averaging 414 pmol/L—well above deficiency thresholds—still showed measurable brain changes. Japan's reference range of >500 pmol/L may better reflect optimal status.
If you're vegan, vegetarian, over 60, or taking medications that affect absorption (metformin, PPIs, H2 blockers), regular B12 monitoring can catch deficiency before symptoms become significant—and before potential neurological damage becomes irreversible.
Testing provides clarity when symptoms are vague, rules out a common and treatable cause of fatigue, cognitive changes, and nerve symptoms, and—given the UCSF findings—suggests that aiming for higher B12 levels (>400-500 pmol/L) rather than just 'not deficient' may be the better approach for protecting brain health.
Frequently Asked Questions
Disclaimer:This information is educational only and not medical advice. Results should be interpreted by your health practitioner in the context of your symptoms and health history. Treatment decisions should be made with your doctor or specialist.