Vitamin B12 deficiency is one of the most common nutritional deficiencies in the UK, affecting an estimated 6% of adults under 60 and nearly 20% of those over 60. Because B12 is essential for making red blood cells, maintaining nerve function, and producing DNA, even mild deficiency can cause wide-ranging symptoms.
What Is Vitamin B12?
Vitamin B12 (cobalamin) is a water-soluble vitamin found almost exclusively in animal products. Unlike most vitamins, B12 is stored in the liver and can last 3–5 years — meaning deficiency can develop slowly and go unnoticed for months or years before symptoms appear.
Vitamin B12 Deficiency Symptoms
Symptoms range from mild fatigue to serious neurological damage. Common signs include:
- Extreme tiredness and fatigue — often described as bone-deep exhaustion
- Pins and needles (paraesthesia) — a hallmark neurological symptom
- Sore, red, swollen tongue (glossitis) — the tongue may look unusually smooth
- Mouth ulcers
- Muscle weakness
- Disturbed vision
- Psychological problems — depression, confusion, memory problems, mood changes
- Balance problems and difficulty walking
- Pale or slightly yellow skin (jaundice)
- Breathlessness and heart palpitations — from anaemia
Important: Neurological symptoms — such as pins and needles, memory loss, and walking difficulties — can become permanent if deficiency is left untreated. If you experience these symptoms, see your GP promptly.
Causes of Vitamin B12 Deficiency in the UK
1. Pernicious Anaemia (Most Common Cause)
Pernicious anaemia is an autoimmune condition where the immune system attacks stomach cells that produce intrinsic factor — the protein needed to absorb B12 in the gut. It affects roughly 1 in 10,000 people in the UK and becomes more common with age. It requires lifelong B12 injections, not supplements.
2. Diet (Vegans and Vegetarians)
B12 is found naturally only in animal foods (meat, fish, eggs, dairy). Vegans who don’t supplement are at high risk. Strict vegetarians who avoid dairy and eggs are also vulnerable. The NHS recommends all vegans take a daily B12 supplement.
3. Metformin Use
Metformin (used for type 2 diabetes) blocks B12 absorption in the gut over time. Long-term metformin users should have their B12 levels checked regularly — NICE guidelines now recommend periodic monitoring.
4. Proton Pump Inhibitors (PPIs)
Long-term use of PPIs (omeprazole, lansoprazole) reduces stomach acid needed to release B12 from food. This is a common but overlooked cause in older adults on long-term acid suppression therapy.
5. Stomach and Gut Conditions
Conditions that affect the gut’s ability to absorb B12 include: Crohn’s disease, coeliac disease, gastric bypass surgery, atrophic gastritis (common in older adults), and H. pylori infection.
6. Age
As we age, stomach acid production declines, reducing B12 absorption from food. Adults over 65 are strongly advised to ensure adequate B12 intake through diet, supplements, or both.
Diagnosing B12 Deficiency
Your GP can test B12 levels with a simple blood test. The NHS defines deficiency as a serum B12 level below 200 pg/mL (148 pmol/L), though some experts argue that levels below 300 pg/mL can still cause neurological symptoms.
Additional tests your GP may order:
- Full blood count (FBC) — to check for megaloblastic anaemia (enlarged, abnormal red blood cells)
- Methylmalonic acid (MMA) and homocysteine — more sensitive markers that rise when B12 is functionally low
- Intrinsic factor antibodies — to confirm pernicious anaemia
- Folate levels — often checked alongside B12 as both cause similar anaemia
NHS Treatment for B12 Deficiency
Treatment depends on the underlying cause:
B12 Injections (Hydroxocobalamin)
For pernicious anaemia or severe deficiency with neurological symptoms, the NHS prescribes hydroxocobalamin injections (a form of B12). The standard loading schedule is:
- Without neurological symptoms: 1 mg IM injection on alternate days for 2 weeks (6 injections), then 1 mg every 3 months for life
- With neurological symptoms: 1 mg IM injection on alternate days until no further improvement, then 1 mg every 2 months for life
Oral B12 Supplements
For diet-related deficiency (e.g., vegans) or mild cases without absorption problems, high-dose oral cyanocobalamin tablets (1,000–2,000 mcg daily) are effective. These bypass the intrinsic factor pathway at high doses and can even treat some cases of pernicious anaemia, though injections remain the gold standard for pernicious anaemia in the UK.
Vitamin B12-Rich Foods
| Food | B12 per serving | % of daily requirement |
|---|---|---|
| Beef liver (75g) | 60 mcg | 2,500% |
| Clams (85g) | 84 mcg | 3,500% |
| Sardines (85g) | 7.6 mcg | 316% |
| Salmon fillet (150g) | 3.2 mcg | 133% |
| Beef steak (100g) | 2.5 mcg | 104% |
| Milk (250ml) | 1.2 mcg | 50% |
| Eggs (2 large) | 1.0 mcg | 42% |
| Cheese, cheddar (50g) | 0.5 mcg | 21% |
| Nutritional yeast (2 tbsp, fortified) | 7.8 mcg | 325% |
| Fortified plant milk (250ml) | 1.0–2.4 mcg | 42–100% |
Daily requirement: 2.4 mcg for adults (NHS/SACN recommendation)
Complications of Untreated B12 Deficiency
Without treatment, B12 deficiency can lead to serious and sometimes irreversible complications:
- Subacute combined degeneration of the spinal cord — a serious neurological condition causing difficulty walking, spasticity, and loss of coordination
- Severe megaloblastic anaemia — requiring transfusion in extreme cases
- Peripheral neuropathy — permanent numbness or weakness in the limbs
- Cognitive decline and dementia — research suggests strong links between low B12 and increased dementia risk
- Increased cardiovascular risk — from elevated homocysteine levels
- Infertility and complications in pregnancy
B12 Deficiency in Pregnancy
Low B12 during pregnancy increases the risk of neural tube defects (alongside folate deficiency), miscarriage, low birth weight, and preterm birth. Pregnant vegans should supplement with B12 and discuss their levels with their midwife or GP.
When to See a GP
See your GP if you experience:
- Persistent unexplained tiredness
- Pins and needles that don’t go away
- A sore or inflamed tongue
- Memory problems or confusion
- Difficulty walking or balance issues
- Low mood or depression
A simple blood test can confirm B12 deficiency quickly. Don’t wait — neurological symptoms can become permanent if treatment is delayed.
This article is for informational purposes only and does not constitute medical advice. Always consult your GP or a qualified healthcare professional for diagnosis and treatment.
Related Health Guides on YourHealthXpert
Explore these related NHS-aligned health guides:
- Anxiety and Depression — B12 deficiency causes low mood, anxiety, and cognitive changes often mistaken for mental illness
- Iron Deficiency Anaemia — iron deficiency often coexists with B12 deficiency; both cause fatigue and anaemia
- Vitamin D Deficiency — commonly coexists with B12 deficiency, especially in older adults and vegans
- Dementia and Alzheimer’s Disease — B12 deficiency causes reversible cognitive impairment that mimics early dementia
- Coeliac Disease — coeliac disease impairs B12 absorption; testing is recommended in unexplained B12 deficiency