From the Guidelines
I strongly recommend starting vitamin B12 supplementation for this 77-year-old female patient with a level of 198 pg/mL, as it indicates a metabolic B12 deficiency, which is a common condition in older adults that can increase the risk of stroke, neuropathy, and dementia. According to the study by 1, metabolic B12 deficiency is frequently missed, and a serum B12 in the normal range is often accepted as ruling out B12 deficiency, but it is essential to consider the patient's plasma total homocysteine or methylmalonic acid levels to diagnose metabolic B12 deficiency. The patient should take oral vitamin B12 (methylcobalamin or hydroxycobalamin) 1000 mcg daily for at least 3 months, then can potentially decrease to 1000 mcg weekly for maintenance if levels normalize.
Key Considerations
- Vitamin B12 deficiency is common in older adults due to decreased stomach acid production, medication interactions (like metformin or proton pump inhibitors), or dietary insufficiency 1.
- Left untreated, B12 deficiency can cause anemia, neurological problems including peripheral neuropathy, balance issues, cognitive decline, and increased cardiovascular risk, including stroke 1.
- The patient should have follow-up testing in 3 months to ensure her levels are improving.
- Additionally, the underlying cause of her deficiency should be investigated, particularly focusing on medication review, evaluation for pernicious anemia, and assessment of dietary intake of B12-rich foods like meat, fish, eggs, and dairy products.
Treatment Options
- Oral vitamin B12 (methylcobalamin or hydroxycobalamin) 1000 mcg daily for at least 3 months, then can potentially decrease to 1000 mcg weekly for maintenance if levels normalize.
- For severe symptoms or malabsorption issues, intramuscular injections may be needed (1000 mcg weekly for 4 weeks, then monthly).
Monitoring and Follow-up
- Follow-up testing in 3 months to ensure her levels are improving.
- Regular monitoring of plasma total homocysteine or methylmalonic acid levels to diagnose metabolic B12 deficiency.
- Assessment of dietary intake of B12-rich foods and consideration of B12 supplementation in patients with ischemic stroke or at high risk of stroke 1.
From the Research
Vitamin B12 Deficiency
- Vitamin B12 deficiency is a common cause of megaloblastic anemia, various neuropsychiatric symptoms, and other clinical manifestations 2.
- Screening for vitamin B12 deficiency may be warranted in patients with one or more risk factors, such as adults older than 75 years 2.
- Initial laboratory assessment should include a complete blood count and serum vitamin B12 level 2.
Diagnosis and Treatment
- Measurement of serum methylmalonic acid can be used to confirm deficiency in asymptomatic high-risk patients with low-normal levels of vitamin B12 2.
- Oral administration of high-dose vitamin B12 (1 to 2 mg daily) is as effective as intramuscular administration for correcting anemia and neurologic symptoms 2.
- Intramuscular therapy leads to more rapid improvement and should be considered in patients with severe deficiency or severe neurologic symptoms 2.
Risk Factors and Prevention
- Adults older than 75 years are at risk of vitamin B12 deficiency 2, 3.
- Vitamin B12 deficiency can be prevented by consuming foods fortified with vitamin B12 or taking vitamin B12 supplements, especially in patients older than 50 years and vegans or strict vegetarians 2.
- Patients who have had bariatric surgery should receive 1 mg of oral vitamin B12 per day indefinitely 2.
Laboratory Assessment
- Serum B12 concentration is useful as a screening marker, and methylmalonic acid or homocysteine can support the diagnosis 4.
- Diagnostic biomarkers for B12 status include decreased levels of circulating total B12 and transcobalamin-bound B12, and abnormally increased levels of homocysteine and methylmalonic acid 5.
- The chosen test often depends on its availability rather than on the diagnostic performance and sensitivity to irrelevant factors interfering with vitamin B12 markers 6.