From the Guidelines
Folic acid can indeed mask vitamin B12 deficiency, as it can improve the anemia associated with B12 deficiency while allowing neurological damage to progress undetected. This is because both vitamins are crucial for DNA synthesis, and folic acid can compensate for this specific function, correcting the hematological manifestations (like macrocytic anemia) that might otherwise alert clinicians to a B12 deficiency 1. However, folic acid cannot substitute for vitamin B12's crucial role in myelin maintenance and neurological function.
Key Considerations
- Folic acid supplementation may mask severe vitamin B12 depletion, making it essential to treat vitamin B12 deficiency immediately before initiating additional folic acid 1.
- In cases of vitamin B12 deficiency with possible neurological involvement, urgent specialist advice should be sought, and hydroxocobalamin should be administered intramuscularly 1.
- The treatment of folic acid deficiency should only be initiated after excluding vitamin B12 deficiency, with oral folic acid 5 mg daily given for a minimum of 4 months 1.
Clinical Implications
- Healthcare providers should measure both vitamin B12 and folate levels before initiating supplementation in patients with unexplained anemia.
- Vitamin B12 deficiency should be treated with appropriate B12 supplementation rather than relying solely on folic acid to address anemia symptoms.
- It is crucial to prioritize the treatment of vitamin B12 deficiency to prevent irreversible neurological damage, especially in cases where B12 deficiency is suspected or confirmed 1.
From the FDA Drug Label
Except during pregnancy and lactation, folic acid should not be given in therapeutic doses greater than 0.4 mg daily until pernicious anemia has been ruled out. Patients with pernicious anemia receiving more than 0.4 mg of folic acid daily who are inadequately treated with vitamin B12 may show reversion of the hematologic parameters to normal, but neurologic manifestations due to vitamin B12 deficiency will progress. Administration of folic acid alone is improper therapy for pernicious anemia and other megaloblastic anemias in which vitamin B12 is deficient.
Yes, folic acid can mask vitamin B12 deficiency. High doses of folic acid can correct the hematologic parameters of B12 deficiency, but will not prevent the progression of neurologic manifestations 2, 2.
From the Research
Folic Acid and Vitamin B12 Deficiency
- Folic acid (FA) can mask vitamin B12 deficiency, as high-dose folic acid supplements can reverse the megaloblastic anemia of vitamin B12 deficiency, but may exacerbate its neuropathological progression 3.
- The use of high-dose folic acid supplements can cause depletion of serum holotranscobalamin, thus exacerbating B12 deficiency 3.
- Cognitive function test scores are lower and blood homocysteine and methylmalonic acid concentrations are higher in people with low B12 and elevated folate than in those with low B12 and nonelevated folate 3.
Diagnosis and Treatment of Vitamin B12 Deficiency
- Vitamin B12 deficiency should be suspected in all patients with unexplained anaemia and/or neurological symptoms, as well as in patients at risk of developing vitamin B12 deficiency such as the elderly and patients with intestinal diseases 4.
- Measurement of plasma cobalamins is suggested as the primary analysis followed by measurement of plasma methylmalonic acid in unsettled cases 4.
- Initial treatment with parenteral B12 was regarded as the first choice for patients with acute and severe manifestations of B12 deficiency, while high-dose oral B12 at different frequencies may be considered for long-term treatment 5.
Risk Factors and Prevention
- Screening may be warranted in patients with one or more risk factors, such as gastric or small intestine resections, inflammatory bowel disease, use of metformin for more than four months, use of proton pump inhibitors or histamine H2 blockers for more than 12 months, vegans or strict vegetarians, and adults older than 75 years 6.
- Patients who have had bariatric surgery should receive 1 mg of oral vitamin B12 per day indefinitely 6.
- Prophylactic B12 supplementation should be considered for specific high-risk groups, such as older adults and others with low B12 intake or conditions that are associated with B12 malabsorption 5.