When Should You Stop Taking Folic Acid In Pregnancy?

Most people can stop taking folic acid at the end of the first trimester, around 12 weeks of pregnancy. After that point, the neural tube — the structure that becomes the brain and spinal cord — has already closed, and the main reason for high-dose folic acid supplementation has passed. But “stop” doesn’t always mean the same thing for everyone, and some people are advised to continue through delivery or even longer.

The short answer is that folic acid matters most in the first 28 days after conception, often before a person knows they are pregnant. That timing is why public health guidance recommends folic acid for anyone who could become pregnant, not just those who already are.

Why Is Folic Acid Most Important in Early Pregnancy?

The neural tube closes between about day 21 and day 28 after conception. That is roughly 3 to 4 weeks into pregnancy — often before a positive test.

Folic acid is a B vitamin (B9) that the body uses to make DNA and support rapid cell division. During neural tube closure, cells are dividing at an extraordinary rate. Without enough folate, that process can be disrupted, leading to neural tube defects such as spina bifida and anencephaly.

This is one of the best-established findings in prenatal medicine. Research consistently shows that adequate folic acid intake before conception and in early pregnancy reduces the risk of neural tube defects. The evidence is strong enough that more than 80 countries require folic acid fortification of certain grain products, and the CDC recommends all people capable of becoming pregnant take 400 micrograms of folic acid daily.

Once the neural tube closes, that specific window is over. Folic acid still supports other aspects of pregnancy — red blood cell production, placental development, general cell growth — but the dramatic protective effect against neural tube defects is tied to that early window.

When Should You Stop Taking Folic Acid In Pregnancy?

For most pregnancies, folic acid supplementation can stop after the first trimester, typically around 12 weeks. At that point, the neural tube has closed and the primary preventive benefit has been achieved.

That said, “can stop” is not the same as “must stop.” Folic acid at standard doses is not harmful in later pregnancy. Many prenatal vitamins contain folic acid and are taken throughout pregnancy. The question is whether continuing provides meaningful additional benefit.

For the general population, the evidence for continuing high-dose folic acid beyond the first trimester is limited. Some research has explored whether folate plays a role in placental function, preterm birth risk, or fetal growth later in pregnancy, but findings are mixed and not strong enough to support a universal recommendation to continue.

There is one important exception. People with certain risk factors — discussed below — are often advised to continue folic acid throughout pregnancy, sometimes at higher doses.

Who Should Continue Folic Acid Beyond the First Trimester?

Some people are advised to continue folic acid for the full duration of pregnancy, or even longer. The reasons vary.

• History of a previous neural tube defect pregnancy. These individuals are typically advised to take a much higher dose — often 4,000 micrograms (4 mg) daily — starting before conception and continuing through at least the first trimester. Some clinicians recommend continuing through pregnancy.
• Certain medications. Drugs that interfere with folate metabolism, such as methotrexate, some anti-seizure medications, and trimethoprim, can increase folate needs. Dosing and duration should be managed by a clinician.
• Maternal conditions. Diabetes, obesity, and malabsorption conditions like celiac disease or Crohn’s disease may increase folate requirements. Clinical guidance varies on how long to continue supplementation.
• MTHFR gene variants. Some people have genetic variations that affect how efficiently the body converts folate to its active form. The clinical significance of these variants is debated, and evidence does not clearly support different supplementation strategies for most people with them.

For these groups, the decision to continue should be made with a healthcare provider. The dose and duration depend on the specific risk factor.

What Happens If You Stop Folic Acid at 12 Weeks?

Nothing harmful happens in a typical pregnancy. The neural tube is closed. The critical window has passed.

Your body still needs folate from food. Leafy greens, legumes, citrus fruits, fortified cereals, and liver are good sources. A normal diet typically provides enough folate for the remainder of pregnancy, though prenatal vitamins are often continued for other nutrients like iron and calcium.

If you stop taking a prenatal vitamin entirely at 12 weeks, you may miss out on iron, calcium, vitamin D, and DHA — nutrients that support later pregnancy. That’s a separate consideration from folic acid. Many people continue a prenatal vitamin through delivery for this reason, even though the folic acid component is no longer serving its primary purpose.

Some people experience no symptoms when they stop folic acid. Others may notice nothing at all. Folate deficiency in later pregnancy is uncommon in people eating a varied diet, though it can occur with poor nutrition or certain medical conditions.

Can You Take Too Much Folic Acid?

Folic acid is water-soluble, so excess amounts are generally excreted in urine. The tolerable upper intake level for adults is 1,000 micrograms (1 mg) per day from supplements and fortified foods — not from natural food sources.

High-dose folic acid — such as the 4 mg dose used in some high-risk pregnancies — exceeds this level but is taken under medical supervision. At these doses, the benefit of preventing neural tube defects is considered to outweigh potential risks for specific high-risk individuals.

Some research has raised questions about very high folate levels and potential interactions with vitamin B12 deficiency, particularly in older adults. The evidence is not strong enough to change recommendations for pregnancy, but it’s a reminder that more is not always better.

For most people, taking a standard prenatal vitamin with 400 to 800 micrograms of folic acid throughout pregnancy is safe and common practice. There is no established harm from doing so.

What About Folate vs. Folic Acid?

Folic acid is the synthetic form of folate, a naturally occurring B vitamin. The body absorbs folic acid more efficiently than natural folate from food — which is why it’s used in supplements and fortified foods.

Some people prefer methylfolate, an active form of folate, believing it’s better absorbed or more natural. The evidence that methylfolate is superior to folic acid for preventing neural tube defects is limited. Folic acid remains the standard recommended form for pregnancy supplementation based on decades of research.

If you have a medical reason to avoid folic acid or prefer a different form, discuss it with your healthcare provider. For most people, standard folic acid is effective and well-studied.

The Bottom Line on When to Stop

For most pregnancies, folic acid supplementation can stop after the first trimester. The critical window for neural tube defect prevention is the first 28 days after conception — often before pregnancy is confirmed.

If you have risk factors for neural tube defects or folate deficiency, your provider may recommend continuing folic acid longer, sometimes at higher doses. Follow their guidance.

If you’re taking a prenatal vitamin, you may continue it for other nutrients even after folic acid’s primary job is done. That’s a personal decision to make with your provider.

The most important takeaway: folic acid matters most before and very early in pregnancy. If you’re planning a pregnancy or could become pregnant, start folic acid now — don’t wait until you have a positive test.