Vitamin B12 Deficiency Symptoms and Treatment
Vitamin B12 deficiency presents with a wide range of symptoms including fatigue, cognitive difficulties, neurological problems, and hematologic abnormalities, and requires prompt treatment with either oral or intramuscular supplementation based on severity and underlying cause. 1
Common Symptoms of Vitamin B12 Deficiency
Hematologic Manifestations
- Abnormal findings on blood count including anemia or macrocytosis 1
- Symptoms of anemia that don't respond to iron treatment, especially during pregnancy or breastfeeding 1
Neurological Symptoms
- Peripheral neuropathy symptoms including pins and needles or numbness (paraesthesia) 1
- Balance issues and falls due to impaired proprioception linked to sensory ataxia 1
- Impaired gait and mobility problems 1, 2
- Tremors 2
- Seizures, particularly in infants 3
Cognitive and Psychiatric Symptoms
- Difficulty concentrating or short-term memory loss (sometimes described as "brain fog") 1, 4
- Depressive symptoms 4
- Fatigue and concentration difficulties 2
Visual Disturbances
Other Manifestations
- Glossitis (inflammation of the tongue) 1
- Developmental delay in infants 3
- Headaches, especially in adolescents 3
Risk Factors for Vitamin B12 Deficiency
Dietary Factors
- Diet low in vitamin B12, especially vegan or vegetarian diets 1, 5
- Limited consumption of fortified foods 1
- Food allergies to eggs, milk, or fish 1
- Restricted diet due to eating disorders 1
Medical Conditions
- Atrophic gastritis affecting the gastric body 1
- Coeliac disease 1
- Autoimmune conditions (thyroid disease, Sjögren syndrome, type 1 diabetes) 1
- Malabsorption syndromes 6
- History of gastrointestinal surgery 6, 4
Medication Use
- Metformin 1, 7
- H2 receptor antagonists 1
- Colchicine 1, 6
- Phenobarbital 1
- Pregabalin 1
- Primidone 1
- Proton pump inhibitors 5
Diagnosis
Testing Approach
- Test for vitamin B12 deficiency in patients with at least one risk factor and one clinical feature 5
- Initial testing includes total serum vitamin B12 level (deficiency if <180 pg/mL) 5
- For borderline levels (180-350 pg/mL), measure methylmalonic acid 5
- Consider measuring homocysteine levels as an additional marker 4
Special Considerations
- Normal B12 levels don't exclude deficiency in patients with strong clinical suspicion 4
- Consider further testing for atrophic gastritis with Helicobacter pylori test and autoantibody evaluation in patients without clear cause of deficiency 5
Treatment Options
For Patients Without Neurological Involvement
- Hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks 1
- Followed by maintenance treatment with 1 mg intramuscularly every 2-3 months for life 1
- Oral vitamin B12 supplementation is an option for most patients and is noninferior to intramuscular administration 5
For Patients With Neurological Involvement
- Hydroxocobalamin 1 mg intramuscularly on alternate days until no further improvement 1
- Then hydroxocobalamin 1 mg intramuscularly every 2 months 1
- Seek urgent specialist advice from neurologist and haematologist 1
Important Treatment Considerations
- Treat vitamin B12 deficiency immediately before initiating folic acid supplementation 1
- Folic acid may mask B12 deficiency and precipitate subacute combined degeneration of the spinal cord 1, 6
- Vitamin B12 deficiency allowed to progress for longer than 3 months may produce permanent degenerative lesions of the spinal cord 6
Treatment Response and Follow-up
- Most patients show clinical improvement of neurological symptoms after receiving vitamin B12 treatment 3, 2
- Recovery of neurological symptoms typically occurs within one month after supplementation 2
- Patients with pernicious anemia require monthly injections for life 6
- Monitor hematocrit and reticulocyte counts during initial treatment 6
Cautions and Pitfalls
- Failure to diagnose and treat can result in irreversible neurological damage 6
- Folic acid doses exceeding 0.1 mg daily may produce hematologic remission in B12-deficient patients but won't prevent neurological manifestations 6
- Vitamin B12 deficiency can be easily overlooked in elderly patients as symptoms may be attributed to comorbidities or aging 4
- Patients should be warned about the danger of taking folic acid in place of vitamin B12 6