Iron and Folic Acid Dosing in Pregnancy
For routine prenatal supplementation, pregnant women should take 30 mg of elemental iron daily and 400-800 μg (0.4-0.8 mg) of folic acid daily throughout pregnancy. 1, 2
Standard Dosing for Low-Risk Women
Folic Acid:
- Take 400-800 μg (0.4-0.8 mg) daily starting before conception and continuing throughout pregnancy 1, 2
- Begin supplementation at least 2-3 months before conception when possible 3
- Continue through 4-6 weeks postpartum or as long as breastfeeding continues 3
- Keep total daily folate consumption below 1 mg per day to avoid masking vitamin B12 deficiency 1, 2
Iron:
- Take 30 mg of elemental iron daily throughout pregnancy 1
- This low-dose regimen (30 mg/day) is as effective as higher doses in preventing iron-deficiency anemia while reducing gastrointestinal side effects 1
- The usual treatment dose for iron deficiency anemia is 60-120 mg of elemental iron per day 4
High-Risk Women Requiring Higher Doses
Folic Acid 4-5 mg daily is indicated for women with: 1, 2, 3
- Personal or family history of neural tube defects
- Previous pregnancy affected by neural tube defects
- Type 1 diabetes mellitus
- Body mass index (BMI) > 30 kg/m²
- Epilepsy on anticonvulsant medications
For high-risk women:
- Take 4-5 mg folic acid daily starting at least 3 months before conception 3
- Continue through the first 12 weeks of gestation 2, 3
- After 12 weeks, reduce to standard dose of 400-800 μg (0.4-0.8 mg) for remainder of pregnancy 2, 3
Special Populations
Post-Bariatric Surgery Patients:
- Require 45-60 mg of elemental iron daily (minimum 45 mg) to maintain ferritin within normal limits 4, 1
- Folic acid 0.4 mg daily is usually sufficient, as doses >0.3 mg are poorly absorbed due to lack of intestinal dihydrofolate reductase 4
- However, if BMI remains >30 kg/m², give 4-5 mg folic acid during periconception period and first trimester 4
Critical Safety Considerations
Avoiding Vitamin B12 Deficiency Masking:
- Folic acid supplementation is unlikely to mask vitamin B12 deficiency, but take folic acid in a multivitamin containing 2.6 μg/day of vitamin B12 to mitigate theoretical concerns 3
- Rule out vitamin B12 deficiency before initiating folic acid doses exceeding 1 mg daily, particularly in older adults 5
Dosing Pitfalls:
- Women requiring >1 mg folic acid should take only one multivitamin tablet per day and add separate folic acid-only tablets to reach the desired dose 3
- Do not exceed one daily dose of multivitamin supplement 3
- Doses greater than 1 mg folic acid do not enhance hematologic effect, and excess is excreted unchanged in urine 6
Monitoring Recommendations
- Measure serum hemoglobin or hematocrit as first-line screening for iron deficiency anemia 1
- For post-bariatric surgery patients, check serum folate, vitamin B12, ferritin, and iron studies at least once per trimester 4
- Higher doses of iron (60-100 mg elemental iron per day) are sometimes prescribed in populations at increased risk for iron deficiency anemia 4
Practical Implementation
Timing matters: Over 50% of pregnancies are unplanned, and neural tube defects develop within the first month after conception, making preconception supplementation critical for all women of reproductive age (12-45 years) 1, 3
Side effects: Iron supplementation commonly causes gastrointestinal symptoms (darkening of stool/urine, teeth staining), but these are generally self-limited 4, 1