B12 Deficiency Signs & Symptoms
Vitamin B12 deficiency can affect multiple body systems. Early recognition can reduce risk of long-term neurological harm.
Explore the Full Symptom Library
Search, filter, and view evidence-based information for all 135 symptoms
When to Seek Emergency Care
- Severe confusion or sudden onset delirium — Seek emergency care immediately
- Complete loss of balance or sudden inability to walk — Seek emergency care immediately
- Severe chest pain or very rapid/irregular heartbeat — Call 999 immediately
- Signs of psychosis (hallucinations, severe paranoia) — Seek emergency psychiatric assessment
- Severe breathing difficulties at rest — Call 999 immediately
- Sudden vision loss or severe visual disturbance — Seek emergency eye assessment
If you experience multiple symptoms from different categories, if symptoms are worsening, or if they are affecting your daily life, consult your GP promptly. Early diagnosis and treatment can prevent irreversible neurological damage. Take our symptom checker results to your appointment.
Symptoms By Body System
Expand each symptom for detail on presentation and evidence references. This page provides an overview before deeper research.
General System
Whole-body signs that may reflect systemic effects of vitamin B12 deficiency.
Key Point: General symptoms are common but non-specific, so pattern recognition matters.
Head, Neck, Throat & Spine
Neurological and neuropsychiatric features affecting cognition, sensation, and central pathways.
Key Point: Neurological signs require prompt assessment due to risk of persistent deficits.
Chest & Upper Limbs
Cardiorespiratory, sensory, pain, and movement features affecting the chest and upper limbs.
Key Point: Mixed vascular and neurological features can overlap in this region.
Abdomen
Gastrointestinal and abdominal manifestations, including sensory and organic findings.
Key Point: Digestive and abdominal findings may indicate both symptom burden and underlying cause.
Reproductive & Urinary
Reproductive and urinary manifestations, including autonomic and pain-related symptoms.
Key Point: Evidence strength varies; clinical context and differential diagnosis are essential.
Lower Limbs
Sensory, gait, balance, and movement symptoms affecting mobility and function.
Key Point: Progressive gait or balance problems should be escalated early.
Interactive Body Map
Select a body region to filter symptoms. Click the same region again, or click outside a region, to show all systems.
Important Clinical Notes
Symptoms Without Anaemia
Neurological and psychiatric symptoms can occur BEFORE blood abnormalities develop. A normal blood count does not exclude B12 deficiency.
Symptom Overlap
Many B12 deficiency symptoms overlap with other conditions. Getting a proper diagnosis requires blood tests, not just symptom assessment.
Treatment Response
Some symptoms (particularly neurological) may take months to improve with treatment, and some damage may be permanent if treatment is delayed.
Experiencing Multiple Symptoms?
Our symptom checker can help assess your risk of B12 deficiency and provide personalised recommendations for discussing with your GP.
Content last reviewed: 2026-03-18.See our Editorial Policy