Does Folic Acid Cause Weight Gain?


Folic acid is a synthetic (man-made) form of folate. It can be taken as a supplement or a drug and it's usually added to some manufactured foods. There is no evidence that taking folic acid, in normal quantities, leads to weight gain. Folic acid is there to make sure everyone gets enough folate.

About folic acid

Folic acid is a man-made form of folate—vitamin B9. Folate is an essential nutrient, important for cell growth, cell division, DNA formation, and production of red blood cells. 

Folate deficiency leads to megaloblastic anaemia, where red blood cells are large, immature, have an unusual structure and are in short supply. Red blood cells produced in megaloblastic anaemia can't carry out their functions and don't last long. Megaloblastic anaemia can also be caused by a deficiency of vitamin B12–another essential nutrient. Folic acid prevents and treats folate deficiency and megaloblastic anaemia.

Role of folic acid

You need folate to be healthy and for your body to function properly. Folic acid boosts folate levels and is recommended.

  • Before and during pregnancy. It's important to take folic acid before getting pregnant and during early pregnancy because your baby needs folate for proper development and to grow its neural tube. The neural tube is what forms the brain and the spinal cord. Taking folic acid during pregnancy prevents premature birth, low birth weight and neural tube defects such as spina bifida and anencephaly.
  • When taking drugs that reduce folate levels. These drugs include methotrexate, a drug used to treat arthritis, psoriasis and Crohn’s disease; sulfasalazine, used to treat ulcerative colitis; and some anti-seizure drugs like carbamazepine.
  • To prevent or treat megaloblastic anaemia from folate deficiency. Taking folic acid is important when you have a high risk of folate deficiency from not getting enough folate, excreting folate rapidly, being unable to absorb, store or use folate. You have a risk of folate deficiency if you
    • have a poor diet–your diet lacks folate from natural foods,
    • have an alcohol use disorder–your body doesn’t absorb and store folate properly and your diet might lack folate,
    • are undergoing renal dialysis–you lose folate during dialysis,
    • cannot convert folate to its active form–you cannot use folate,
    • are pregnant–your blood volume increases and you need more folate to produce red blood cells,
    • have a nutrient absorption, disorder like tropical sprue, inflammatory bowel disease or celiac disease.

Why take folic acid?

Folate is an essential nutrient found in many natural foods. But, it is hard to get the required amount of folate from food because cooking heat destroys folate and the intestine doesn't absorb natural folate easily. 

Folic acid supplies folate in adequate amounts to the body. What's more, folic acid is stable and easily absorbed by the intestines, making it an excellent folate substitute. If folic acid didn't exist, people at risk of, or with folate deficiency would need to eat a lot of folate-rich foods every day to meet their folate requirements. This is not ideal or possible for everyone.

Side effects of folic acid consumption 

Folic acid is safe to consume and side effects are not common, especially with low quantities of folic acid. So, you might not experience any side effects. The side effects of folic acid, when they occur, are usually mild and brief. Some side effects people have reported are:

  • feeling bloated
  • loss of appetite
  • farting
  • nausea
  • bitter or sour taste in the mouth
  • irritability 
  • altered sleep patterns
  • overactivity 
  • confusion
  • difficulty concentrating
  • impaired judgement.

You can check the leaflet in your drug or supplement packet for other possible side effects of folic acid.

An allergic reaction is a rare but severe side effect of folic acid. Contact your doctor for immediate treatment if you experience a skin rash, skin redness and itch, tightness in your chest, difficulty breathing, wheezing, or a swollen mouth, tongue or lip.

You should consult your doctor before taking folic acid if you have a risk of cancer or vitamin B12 deficiency, or if you use other drugs. Excessive intake of folic acid could speed up the progression of cancers, like colorectal and prostate cancers, in at-risk people. 

Also, folic acid masks vitamin B12 deficiency because folic acid treats the anaemia from vitamin B12 deficiency but does not treat the nerve damage. It's important to rule out this deficiency before you start taking folic acid. 

Folic acid prevents some drugs from working. Ask your doctor or pharmacist if you can take folic acid with your current medications.

Does folic acid cause weight gain?

There's no evidence that folic acid, alone, causes weight gain. A study¹ found that taking excess folic acid led to extra weight gain in rats who were placed on a high fat diet. The excess folic acid encouraged more fat storage in rats that were already on a high fat diet. There was no extra weight gain in rats that were on a high fat diet but took normal quantities of folic acid and those that were on a low fat diet with excess folic acid.

Another study² found that low folate intake and low folate levels in the blood were associated with obesity and fat accumulation in humans. It's possible that a low folate level causes fat accumulation. Another possibility is that fat accumulation reduces the amount of folate in the body.

These studies show no links between folic acid intake and weight increase in humans.

Taking Folic Acid

You can get folic acid from dietary supplements, over the counter drugs or prescription drugs. You can also get folic acid from foods fortified with folic acid (manufactured foods that folic acid was added to) like pasta, bread, breakfast cereals, rice, flour, and cornmeal. Fortification of common foods with folic acid has reduced the incidence of folate deficiency and complications like neural tube defects. This practice has been adopted by many countries. People now meet their folate requirements when they eat fortified foods. To know if any food has folic acid, check the list of nutrients on the packet.

Daily recommended allowance

It's important to get a substantial amount of folate each day to avoid folate deficiency. The daily recommended allowance of folate is the amount of folate you need to meet your body's requirements and to prevent deficiency. The daily recommended allowance of folate is 400mcg for adults and 600mcg during pregnancy. The daily upper limit of folate is 1000mcg. This is the maximum amount of folate you should take each day. 

You will typically need a smaller amount of folic acid (60% of folate) to meet your folate needs, since folic acid is stable and easily absorbed. So, 400mcg of folate is equivalent to 240 mcg folic acid. Ask your doctor for the right amount of folic acid you need to take. 

Consumption Method

There are many ways to fulfil your daily folate requirements. You can get folate from natural foods or you can take folic acid from supplements, or drugs or fortified foods.

Over the counter

You can get folic acid as a standalone supplement or from multivitamin supplements. You can also get a prescription for folic acid or get it without one. It's important to know the difference between a supplement and a drug before making a choice. Ask your doctor which is best for you.

Folic acid in natural foods

Folate, the natural form of folic acid, has many sources: green leafy vegetables like brussels sprouts and spinach, oranges, peanuts, black eyed peas, animal protein like beef liver, eggs, dairy products, and seafood. The best sources of folate are beef liver, spinach and black eyed peas.


There is no evidence that taking folic acid can make you gain weight. Folic acid is important because it helps you meet your daily folate needs. Folic acid is added to some common foods to make sure everyone gets enough folate. You might need extra folic acid from supplements or drugs if you have low folate levels or are at risk of folate deficiency. Folic acid is safe, its side effects are uncommon.


  1. Kelly K, Kennelly J, Ordonez M, Nelson R, Leonard K, Stabler S, et al. Excess Folic Acid Increases Lipid Storage, Weight Gain, and Adipose Tissue Inflammation in High Fat Diet-Fed Rats. Nutrients [Internet]. 2016 [cited 2022 Aug 11];8:594. Available from:
  2. Mlodzik-Czyzewska MA, Malinowska AM, Chmurzynska A. Low folate intake and serum levels are associated with higher body mass index and abdominal fat accumulation: a case control study. Nutr J [Internet]. 2020 [cited 2022 Aug 11];19:53. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Roseline Akpa

Bachelor of Science degree in Human Physiology, Ahmadu Bello University, Nigeria

She is a freelance health writer interested in mental health, holistic health, and health tech.

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