From the Guidelines
Vitamin B12 deficiency can cause a range of symptoms including abnormal findings on a blood count, cognitive difficulties, and eyesight problems related to optic nerve dysfunction, such as blurred vision, as noted in the most recent guideline summary 1. These symptoms develop gradually as B12 levels decline, often taking years to become noticeable. The deficiency affects multiple body systems because B12 is essential for red blood cell formation, neurological function, and DNA synthesis. Some common symptoms and signs of vitamin B12 deficiency include:
- Abnormal findings, such as anaemia or macrocytosis, on a blood count
- Cognitive difficulties, such as difficulty concentrating or short term memory loss
- Eyesight problems related to optic nerve dysfunction, including blurred vision Left untreated, it can lead to severe neurological damage, anemia, and other complications. People at higher risk include older adults, vegetarians and vegans, those with gastrointestinal disorders like Crohn's disease or celiac disease, and individuals who have had gastrointestinal surgery. Treatment typically involves B12 supplements (oral, sublingual, or injections) depending on the severity and cause of the deficiency, with hydroxocobalamin 1 mg intramuscularly on alternate days until there is no further improvement, then administer hydroxocobalamin 1 mg intramuscularly every 2 months for people with neurological involvement, as recommended by NICE 1. Blood tests measuring serum B12 levels, complete blood count, and methylmalonic acid can confirm the diagnosis before starting treatment.
From the FDA Drug Label
CLINICAL PHARMACOLOGY Vitamin B12 is essential to growth, cell reproduction, hematopoiesis, and nucleoprotein and myelin synthesis. Intrinsic factor deficiency causes pernicious anemia, which may be associated with subacute combined degeneration of the spinal cord Prompt parenteral administration of vitamin B12 prevents progression of neurologic damage.
The symptoms of B12 deficiency include pernicious anemia and subacute combined degeneration of the spinal cord.
- Pernicious anemia is caused by intrinsic factor deficiency.
- Subacute combined degeneration of the spinal cord is a neurologic damage that can be prevented by prompt parenteral administration of vitamin B12. 2
From the Research
Symptoms of Vitamin B12 Deficiency
The symptoms of vitamin B12 deficiency can be varied and affect different systems in the body. Some of the common symptoms include:
- Megaloblastic anemia, which is a condition characterized by the production of large, immature red blood cells that are not able to function properly 3
- Neuropsychiatric symptoms, such as cognitive impairment, psychosis, and nervous system problems 3, 4, 5
- Fatigue, weakness, and shortness of breath due to anemia 5
- Digestive problems, such as diarrhea, constipation, and loss of appetite 5
- Numbness or tingling in the hands and feet due to nerve damage 5
Risk Factors for Vitamin B12 Deficiency
Certain individuals are at a higher risk of developing vitamin B12 deficiency, including:
- Older adults, particularly those over 75 years of age 3
- Vegetarians and vegans, who do not consume animal products that are rich in vitamin B12 3, 4
- Individuals with gastrointestinal disorders, such as celiac disease or Crohn's disease, that can impair vitamin B12 absorption 3, 5
- Individuals who have had gastric or small intestine resections, which can reduce vitamin B12 absorption 3
- Individuals taking certain medications, such as metformin or proton pump inhibitors, that can interfere with vitamin B12 absorption 3
Diagnosis and Treatment of Vitamin B12 Deficiency
Diagnosis of vitamin B12 deficiency typically involves a combination of physical examination, medical history, and laboratory tests, including:
- Complete blood count (CBC) to check for anemia 3
- Serum vitamin B12 level to check for deficiency 3
- Measurement of serum methylmalonic acid to confirm deficiency in asymptomatic high-risk patients with low-normal levels of vitamin B12 3 Treatment of vitamin B12 deficiency typically involves supplementation with oral or intramuscular vitamin B12, and may also involve addressing underlying causes of deficiency, such as gastrointestinal disorders or dietary deficiencies 3, 5