Folic Acid: Uses, Dosage & Side Effects

Folic acid (vitamin B9) is a water-soluble B vitamin essential for nucleotide synthesis, DNA replication, and cell division. It prevents neural tube defects and supports hematopoiesis.

• Folate deficiency anemia
• Pregnancy and preconception (neural tube defect prevention)
• Methotrexate toxicity reduction
• High homocysteine reduction (adjunctive)
• Malabsorption disorders (celiac, Crohn's, post-bariatric surgery)
• Chronic hemolytic anemia
• Certain hematologic malignancies (adjunctive)

Pregnancy and Preconception:

• Standard risk: 0.4-0.8 mg daily
• High-risk (previous NTD, anticonvulsant use, diabetes): 4 mg daily
• Begin at least one month preconception

Folate Deficiency Anemia:

• 1 mg daily until hematologic recovery
• Then maintenance: 0.4 mg daily or dietary sources

Methotrexate Adjunctive:

• 1 mg daily on days NOT taking methotrexate
• OR 5 mg once weekly (24 hours after weekly methotrexate dose)
• Reduces toxicity and GI side effects significantly

High Homocysteine:

• 0.4-5 mg daily (adjunctive to vitamin B12 and B6)

Common: Generally very well tolerated; GI upset rare Rare: Allergic reactions, sleep disturbances, hyperactivity (in children)

• Vitamin B12 deficiency (untreated) with neurologic manifestations
• Pernicious anemia (without concurrent B12 therapy)
• Severe allergic reactions to folic acid (rare)

• Methotrexate: folic acid mitigates toxicity; schedule dose appropriately
• Anticonvulsants (phenytoin, carbamazepine, valproate): reduce folate absorption; monitor levels
• Trimethoprim: inhibits folate synthesis; monitor for deficiency
• Sulfasalazine: reduces folate absorption; increase supplementation
• Oral contraceptives: may reduce folate status; monitor in high-risk patients

USPSTF recommends 0.4-0.8 mg daily for women of childbearing age (preconception). Reduces neural tube defect risk by ~70%. Combination with B12 and B6 may reduce homocysteine; cardiovascular benefit unclear from RCTs.

• Baseline assessment before initiating therapy
• Regular clinical follow-up per indication
• Laboratory parameters as specified in sections above
• Drug interaction screening at each visit

Dosing adjustments may be necessary in:

• Renal impairment
• Hepatic impairment
• Elderly patients
• Pregnancy and lactation
• Pediatric patients

• Take exactly as directed; do not modify dose without consulting healthcare provider
• Report any unusual symptoms or adverse effects
• Maintain regular follow-up appointments
• Store at room temperature away from moisture and light
• Keep out of reach of children

Disclaimer: This information is for educational purposes only and should not substitute for professional medical advice. Always consult with a qualified healthcare provider before starting, stopping, or modifying any medication.