Folic Acid Deficiency

Key Features

• Folic acid present in most fruits and vegetables (especially citrus fruits and green leafy vegetables)

• Daily requirements of 50–100 mcg/day usually met in the diet

• Total body stores of folate are enough to supply requirements for 2–3 mo

• Most common cause of folate deficiency is inadequate dietary intake, which occurs in

  • Persons with alcohol use disorder

  • Anorectic patients

  • Persons who do not eat fresh fruits and vegetables

  • Those who overcook food

• Other causes

  • Decreased absorption due to

    • Medications, eg, phenytoin, sulfasalazine, trimethoprim-sulfamethoxazole

    • Gastrointestinal mucosal atrophy

  • Increased requirement (chronic hemolytic anemia, pregnancy, exfoliative skin disease)

  • Loss (dialysis)

  • Inhibition of reduction to active form (methotrexate therapy)

Clinical Findings

• Megaloblastic anemia, which may be severe

• Glossitis and vague GI disturbances (eg, anorexia, diarrhea)

• No neurologic abnormalities, unlike vitamin B₁₂ deficiency

Diagnosis

• Megaloblastic anemia identical to that in vitamin B₁₂ deficiency (eg, macro-ovalocytes, hypersegmented neutrophils (see Vitamin B12 Deficiency)

• Red blood cell folate level < 150 ng/mL

• Serum vitamin B₁₂ level normal

• Distinguish from vitamin B₁₂ deficiency as well as from pure anemia of liver disease (macrocytic anemia with target cells but no megaloblastic changes)

Treatment

• Folic acid, 1 mg orally once daily, for patients with folic acid deficiency or increased folic acid requirements

• Rapid improvement in sense of well-being, reticulocytosis in 5–7 days, and total correction of hematologic abnormalities within 2 months