Vitamin B12 Deficiency: Symptoms, Testing and Why Vegetarians Are at Higher Risk

Vitamin B12 deficiency is one of the slower-developing deficiencies, which is part of why it's often caught late — your body stores several years' worth of B12, so symptoms can take a long time to appear even when intake has been low for a while.

Symptoms worth knowing

• Persistent fatigue and weakness
• Tingling or numbness in hands and feet
• Memory difficulties or trouble concentrating
• Pale or slightly yellowish skin
• A sore or unusually smooth tongue

None of these are specific to B12 alone, which is exactly why testing — rather than guessing from symptoms — is the more reliable path.

Why vegetarians and vegans carry higher risk

B12 is naturally found almost exclusively in animal products. Plant-based diets without fortified foods or supplementation carry meaningfully higher deficiency risk over time — one of the more well-established nutritional gaps associated with strict vegetarian or vegan eating patterns.

How the test works

A standard blood test measures serum B12 directly. In borderline cases, doctors sometimes add methylmalonic acid (MMA) or homocysteine — markers that rise specifically when B12 is functionally low, even if serum B12 looks borderline-normal.

Who else is at elevated risk

• Older adults, due to reduced stomach acid needed for B12 absorption
• People on long-term metformin (used for diabetes), which can reduce B12 absorption
• Anyone with digestive conditions affecting nutrient absorption

The practical takeaway

Because deficiency builds slowly and symptoms are so nonspecific, B12 is a reasonable test to include periodically for anyone following a largely plant-based diet — rather than waiting for symptoms to become obvious enough to prompt testing.

This is general health information, not medical advice. Always talk to a qualified healthcare professional about your own results.