When to Start Folic Acid Before Pregnancy
Folic acid (vitamin B9) is essential for forming the fetal neural tube — the foundation of the brain and spinal cord. A deficiency raises the risk of birth defects like neural tube defects (NTDs). The catch is that the neural tube closes within the first 4-6 weeks of pregnancy, often before a pregnancy is even confirmed. That's why it's important to start folic acid before you start trying to conceive.
Recommended timing and dose
The general recommendation is to start taking 400-600 mcg of folic acid daily at least 1 month before conception, ideally 3 months ahead. People at higher risk — with a prior NTD-affected pregnancy, diabetes, or anti-seizure medication use — may need a much higher dose of 4,000 mcg (4 mg) per day to lower recurrence risk, and this should only be taken under a doctor's prescription and supervision.
Keep taking it after conception, too
Folic acid is typically continued through at least the first 12 weeks of pregnancy, or longer per your OB-GYN's guidance. This calculator provides general timing and dosage guidance for reference — for the exact dose that's right for your health situation, confirm with an OB-GYN visit.
Frequently Asked Questions
The neural tube forms in the very first weeks of pregnancy (weeks 4-6), often before you even know you're pregnant. That's why anyone planning a pregnancy is advised to start folic acid at least 1 month, ideally 3 months, ahead of time.
For people with a prior pregnancy affected by a neural tube defect, or risk factors like diabetes or anti-seizure medication, a higher dose of 4,000 mcg (4 mg) per day is recommended under a doctor's supervision to lower recurrence risk.