How long does folic acid take to work?

Ensuring your body has the right amount of folate (the natural form of the synthetic folic acid) is important for a number of core bodily functions. Folic acid is well‑known for its role in pregnancy support, especially in helping to reduce the risk of neural tube defects in a developing foetus,¹ but it is also valuable for both men and women in supporting healthy blood formation, immune system function and general cell renewal. 

In this article, we explore when you can expect to start seeing the impact of folic acid supplementation and when the best time to take it is.

How Long Does It Take for Folic Acid to Work?

When you take a folic acid supplement or eat folate‑rich foods, your body begins metabolising the nutrient within a few hours. Because folic acid is water‑soluble, regular daily intake is essential for maintaining adequate levels; unlike fat-soluble vitamins, any unused water-soluble vitamins leave the body through urine, preventing their storage in the body.² Consistency is therefore key in order to see noticeable effects.

It’s worth noting that you’re most likely to spot improvements after taking folic acid supplements if you weren’t getting enough of the nutrient already. If you were only slightly deficient, or already getting enough folate from your diet, changes may be more subtle and harder to notice. With that said, there are some timelines to be aware of.

For more immediate benefits relating to the formation of red blood cells, you may start to notice subtle changes within weeks – such as feeling a bit more energetic and alert, experiencing less lightheadedness or having better recovery times after minor exertion – but these will depend on your baseline folate status, your diet and your overall health. The more deficient you were before taking supplements, the more likely it is that you’ll notice these changes.

However, for longer‑term benefits – such as improved psychological resilience, stronger immune responses or the prevention of neural tube defects in early pregnancy – it can take several weeks, and sometimes even months, of continuous intake before optimal levels are reached and noticeable effects appear.³ 

In the case of preventing birth defects with folic acid, it’s estimated that to protect a developing embryo’s neural tube, folate must increase significantly in the red blood cells. For some, this can take more than four weeks of supplementation.⁴ If you stop taking folic acid, the level of folate decreases once again, and this is why it is so important to make a consistent habit of taking it daily.

When Should You Take Folic Acid?

If you suspect a folate deficiency – for example due to poor diet, certain health conditions or medications that interfere with absorption – it is generally a good idea to start taking folic acid as soon as possible and to do so under the supervision of a health‑care professional. However, there are some factors to take into account when deciding how to fit it into your routine.

Time of day – Most people can take their folic acid supplement once each day, preferably at the same time of day to support habit and consistency. Taking it with a light meal can help to reduce the risk of nausea, which some people experience. If you notice mild stomach upset, try taking the tablet with breakfast or another meal rather than on an empty stomach.

Sleep and nausea considerations – Some people notice increased alertness after taking folic acid, so taking it earlier in the day may help avoid any potential impact on sleep. When mild nausea occurs, it is usually related to stomach sensitivity rather than the nutrient itself. Taking folic acid with a meal or at a different time of day may improve tolerance by reducing irritation to an empty stomach.

Lifestyle considerations – Maintaining consistent daily intake alongside a balanced diet of leafy greens, legumes and fortified grains will support the steady rise of folate status. Consider setting an alarm or linking the supplement to another daily habit (such as your morning tea or coffee) to help yourself remember to take it.

When Is the Best Time to Take Folic Acid for Pregnancy?

One of the most critical uses of folic acid is in reducing the risk of neural tube defects (NTDs) such as spina bifida in an unborn baby. The neural tube begins to form very early in pregnancy – about 28 days after conception, often before a woman knows she is pregnant.⁵ For this reason, major guidelines recommend starting folic acid supplementation before conception and continuing through the first 12 weeks of pregnancy.⁶

Ideally, if you are planning to conceive, you should begin taking about 400 µg (0.4 mg) of folic acid daily at least one month to three months before trying to conceive, and continue through the first trimester.⁷ If morning sickness or nausea arises after conception, taking the same supplement with a small snack or later in the day may help you stay consistent, as nausea is often influenced by stomach sensitivity and timing relative to meals rather than the folic acid itself. Because you are supporting an early, rapid phase of cell development, ensuring you have sufficient levels of folate is vital for the protective effect.

In summary, while some benefits of folic acid (such as blood cell formation or energy support) may become evident over weeks, the prevention of neural tube defects demands that supplementation be started before pregnancy and maintained consistently through the early weeks.

Final Thoughts

Folic acid is a safe and effective supplement when used appropriately, helping to support blood formation, immune function, general cell renewal and, most critically in pregnancy, helping to protect a developing baby’s nervous system. The key is making it a consistent daily habit, taking it at a time of day which suits you, and if applicable, beginning well before conception. Always consult your health‑care provider for personalised advice, especially if you have special health circumstances or are taking other medications.

References 

1. Centers for Disease Control and Prevention. (n.d.). Folic Acid: About. Retrieved from https://www.cdc.gov/folic-acid/about/index.html
   
2. Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academies Press.
   
3. Johns Hopkins Medicine. (n.d.). Folic Acid for a Healthy Baby. Retrieved from https://www.hopkinsmedicine.org/health/conditions-and-diseases/folic-acid-for-a-healthy-baby
   
4. National Health Service. (n.d.). How and when to take folic acid. Retrieved from https://www.nhs.uk/medicines/folic-acid/how-and-when-to-take-folic-acid/
   
5. U.S. Preventive Services Task Force. (2025). Folic Acid Supplementation to Prevent Neural Tube Defects. Retrieved from https://www.uspreventiveservicestaskforce.org/recommendation/folic-acid-for-the-prevention-of-neural-tube-defects-preventive-medication
   
6. Mayo Clinic. (2024). Folic Acid (Vitamin B9): Uses, Side Effects, Dosage.https://www.mayoclinic.org/drugs-supplements/folic-acid/art-20364625
7. National Institutes of Health. (2023). Folate (Folic Acid) – Fact Sheet for Health Professionals. Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/