From the Guidelines
Yes, low vitamin B12 levels can cause confusion, as evidenced by the recent guideline summary published in the BMJ in 2024 1. Vitamin B12 deficiency affects the nervous system, including brain function, which can lead to cognitive symptoms like confusion, memory problems, difficulty concentrating, and even dementia-like symptoms in severe cases. This happens because B12 is essential for maintaining healthy nerve cells and for producing myelin, the protective covering around nerves. When B12 levels are low, nerve transmission becomes impaired, affecting brain function. 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 (sometimes described as “brain fog”), which can also be symptoms of delirium or dementia
- Eyesight problems related to optic nerve dysfunction, including blurred vision Treatment typically involves B12 supplementation, and it is crucial to test for vitamin B12 deficiency in a timely manner, especially in individuals presenting with symptoms commonly attributed to the condition, as highlighted in the guideline summary 1. People at higher risk include older adults, vegetarians, vegans, those with gastrointestinal disorders, and individuals taking certain medications. If you're experiencing confusion and suspect B12 deficiency, it's essential to get your levels checked through a blood test, as early treatment can prevent permanent neurological damage.
From the FDA Drug Label
Vitamin B12 deficiency that is allowed to progress for longer than three months may produce permanent degenerative lesions of the spinal cord. Neurologic manifestations will not be prevented with folic acid, and if not treated with Vitamin B12, irreversible damage will result.
Low Vitamin B12 levels can cause neurologic manifestations, but the provided drug labels do not explicitly state that low Vitamin B12 can cause confusion.
- The labels mention that Vitamin B12 deficiency can produce permanent degenerative lesions of the spinal cord and irreversible damage if left untreated.
- However, they do not provide a direct link between low Vitamin B12 levels and confusion. 2 3
From the Research
Vitamin B12 Deficiency and Confusion
- Vitamin B12 deficiency can cause various neuropsychiatric symptoms, including confusion, as stated in the study 4.
- The deficiency can affect individuals at all ages, but most particularly elderly individuals, and can lead to cognitive disorders, as mentioned in the study 5.
- Neurological manifestations of vitamin B12 deficiency include subacute combined degeneration of spinal cord, sensomotor polyneuropathy, optic nerve neuropathy, and cognitive disorders, as described in the study 6.
- Low vitamin B12 levels have been linked to impaired cognition and memory, and replacement therapy may improve patient cognition outcomes, as shown in the study 7.
- Vitamin B12 levels within the current normal range may be associated with measurable evidence of neurological injury or dysfunction in older adults, as found in the study 8.
Risk Factors and Diagnosis
- Screening for vitamin B12 deficiency may be warranted in patients with one or more risk factors, such as gastric or small intestine resections, inflammatory bowel disease, or use of certain medications, as stated in the study 4.
- Diagnostic biomarkers for vitamin B12 status include decreased levels of circulating total B12 and transcobalamin-bound B12, and abnormally increased levels of homocysteine and methylmalonic acid, as mentioned in the study 5.
- Measurement of serum methylmalonic acid should be used to confirm deficiency in asymptomatic high-risk patients with low-normal levels of vitamin B12, as recommended in the study 4.
Treatment and Management
- Oral administration of high-dose vitamin B12 is as effective as intramuscular administration for correcting anemia and neurologic symptoms, as stated in the study 4.
- Patients who have had bariatric surgery should receive 1 mg of oral vitamin B12 per day indefinitely, as recommended in the study 4.
- Vitamin B12 replacement therapy may improve cognitive impairment in patients with vitamin B12 deficiency, as shown in the study 7.