Vitamin B12 deficiency: Why it's more common than you think

Dr. Charalampos Romanos · April 14, 2026 · 5 min read

Vitamin B12 deficiency is a silent suffering. Many people have a deficiency and don't know about it. The problem is: B12 deficiency can cause irreversible neurological damage if not recognised. As a GP in Zurich, I see far too often patients in whom this deficiency is diagnosed too late.

Why B12 deficiency is so common

There are several reasons. First: vegetarians and vegans. B12 is found mainly in animal products — meat, fish, eggs, dairy products. If you avoid these, you're automatically at risk. Second: gastrointestinal problems. The stomach intrinsic factor system is necessary to absorb B12. Low stomach acid, gastric mucosa inflammation, or bowel problems impair this. Third: certain medications such as metformin or proton pump inhibitors.

The neurological symptoms you shouldn't ignore

Here's the dangerous part: B12 deficiency causes paraesthesias — tingling sensations in extremities. Patients often think of carpal tunnel syndrome or other problems. But it can also lead to subacute combined degeneration — a form of neuropathy that can become permanent. Balance problems, confusion, even psychosis can be signs of B12 deficiency.

Serum B12 is not the whole picture

This is my big point: many doctors only check B12 serum. But when the body's B12 stores are depleted, the serum value can still be "normal". I also order methylmalonic acid and homocysteine. If these are elevated, it means B12 deficiency at the cellular level — regardless of the serum value.

Pernicious anaemia: When the immune system is the problem

Pernicious anaemia is an autoimmune disease in which the body produces antibodies against intrinsic factor. This completely prevents B12 absorption in the stomach. This is not a nutritional problem — it's a medical problem that can only be solved with B12 injections.

Oral, injection or infusion: What works best

For vegetarians with depleted stores, oral supplementation can work — high-dose and regular. But for patients with absorption problems or pernicious anaemia, we need B12 injections or infusions. Intramuscular works immediately and bypasses the absorption problem completely. I almost always see good success with it.

Long-term monitoring and maintenance therapy

B12 deficiency is not a one-time treatment. Patients with absorption problems need regular injections or infusions. This is no shame — it's medical necessity. I recommend my patients preventive monitoring to prevent relapses and keep their health status optimal.