Can Folic Make You Feel Sick? Understanding the Causes and Solutions

October 10, 2025 •

4 min read

While generally safe and well-tolerated, some individuals report feeling sick, experiencing nausea, or other mild side effects when taking folic acid supplements. This is often tied to high dosages, the timing of the dose, or other components in a multivitamin. Fortunately, these effects are usually temporary and easily manageable, with simple adjustments often making a significant difference.

Quick Summary

Feeling sick from folic acid is possible, but typically mild and rare, especially at standard doses. High dosages, intake on an empty stomach, or other combined ingredients can increase the risk of discomfort.

Key Points

Dosage is Key: High doses of folic acid, often exceeding 1 mg per day, are more likely to cause side effects like nausea.
Take with Food: Consuming the supplement with a meal or snack can significantly reduce the chances of an upset stomach.
Timing Matters: Taking folic acid before bed can help minimize the perception of nausea for some individuals.
Check for Other Ingredients: If taking a prenatal or multivitamin, other components like iron are often the primary cause of gastrointestinal upset.
Don't Stop Without Consulting: It is crucial to speak with a healthcare provider before stopping folic acid, especially during pregnancy or if on a medication like methotrexate.
Watch for Overdose Signs: Signs of overdose can include nausea and vomiting, and require immediate medical attention.

Folic acid, the synthetic form of vitamin B9 (folate), is a crucial nutrient for cell growth and metabolism, particularly important during pregnancy to prevent birth defects like spina bifida. For most individuals, taking folic acid supplements is without issue. However, some people may experience mild gastrointestinal discomfort, including nausea. Understanding why this happens and what can be done is key to managing any discomfort without compromising your health goals.

The Link Between Folic Acid Dosage and Nausea

Side effects from folic acid are infrequent at the recommended daily allowances (RDA). For example, the RDA for adults is 400 mcg daily. The risk of nausea and other gastrointestinal issues, such as bloating, gas, and stomach cramps, increases with higher dosages. Individuals on therapeutic doses, such as those with certain medical conditions or those prescribed a higher amount by a doctor, are more likely to notice these symptoms. An overdose can also lead to more pronounced sickness, vomiting, and abdominal pain.

The Role of Other Ingredients in Multivitamins

Folic acid is often one component of a broader multivitamin or prenatal vitamin. In many cases, it is not the folic acid itself that causes the upset stomach, but other ingredients, most notably iron. Prenatal vitamins commonly include iron to prevent anemia, and this mineral can cause significant gastrointestinal side effects like constipation, diarrhea, and nausea. Some individuals taking gummy vitamins, which often contain less or no iron, report experiencing less nausea, suggesting iron was the root cause of their discomfort.

What to Do If Folic Acid Makes You Feel Sick

If you find yourself feeling sick after taking your supplement, there are several straightforward adjustments you can make:

Take with food: Avoid taking folic acid on an empty stomach. Consuming it with a meal or a snack can buffer the stomach and reduce the likelihood of nausea.
Change the time of day: Try taking the supplement right before bed. This can help you sleep through any mild, temporary nausea.
Split the dose: If your dosage allows, consider taking smaller amounts throughout the day instead of a single large dose.
Try a different formulation: Some people may be sensitive to certain tablet coatings or inactive ingredients. If using a combination pill like a prenatal, consider a different brand or formulation. Switching from a large pill to a chewable or liquid supplement might also help with nausea that is triggered by swallowing.
Consider a methylated form: Some people have a genetic variation (MTHFR polymorphism) that affects how their body processes folic acid. For these individuals, supplements with L-5-methyltetrahydrofolate (L-5-MTHF), the active form of folate, may be more easily tolerated and beneficial.

Comparison of Folic Acid Intake Strategies


Strategy	Pros	Cons	Best For	Considerations
Taking with Food	Reduces stomach irritation; improves absorption.	Requires planning around mealtimes.	Mild nausea; sensitive stomachs.	Take with a substantial meal, not just a small snack.
Taking at Bedtime	You sleep through potential nausea.	May still cause overnight discomfort for some.	Morning sickness; nighttime nausea.	Can be combined with taking with a light snack.
Splitting the Dose	Lessens the impact on the digestive system.	Requires taking multiple pills a day.	High-dose users; severe sensitivity.	Only do this under a doctor's supervision.
Using Alternative Form	Addresses issues with inactive ingredients; may help those with MTHFR gene variation.	Requires a new product purchase; potentially different dosages.	Persistent nausea; MTHFR sensitivity.	Consult a doctor before switching to ensure efficacy.

When to Seek Medical Attention

While mild nausea is typically not a cause for alarm, certain symptoms should prompt immediate medical consultation:

Allergic reaction: Severe allergic reactions are rare but possible. Look for hives, a rash, itching, wheezing, or swelling of the face, lips, or tongue, and seek immediate help if these occur.
Overdose symptoms: If you suspect you have taken too much folic acid, and experience significant nausea, vomiting, or diarrhea, contact a healthcare provider.
Masking B12 deficiency: Taking high-dose folic acid over a long period can mask the symptoms of a vitamin B12 deficiency. If left untreated, this can lead to severe neurological damage. If you have been taking a high dose and experience symptoms like numbness, tingling, or weakness, see a doctor.
Persistent issues: If your nausea or other side effects persist despite trying different management strategies, your doctor can assess the cause and recommend a different approach.

The Paradox: When Folic Acid Helps Nausea

Interestingly, folic acid is sometimes used to reduce nausea and other side effects in patients taking the medication methotrexate. Methotrexate can deplete the body's folate levels, causing side effects. In this context, supplemental folic acid can mitigate these negative effects, highlighting the complex and situation-dependent nature of medication side effects.

Conclusion

In short, while it is possible for folic acid to make you feel sick, especially at higher doses or when combined with other supplements like iron, it is not a common side effect for most people. The discomfort is usually mild and can often be resolved with simple changes to how and when you take your supplement. The benefits of adequate folic acid intake, particularly for pregnant women and those with certain medical conditions, almost always outweigh the risk of mild, temporary side effects. Always consult with a healthcare provider if your symptoms are severe, persistent, or if you have any concerns about your dosage or overall health.

For more information on managing supplement side effects, the Mayo Clinic offers reliable resources.

Frequently Asked Questions

While uncommon, it is possible for some people to experience mild nausea or an upset stomach, particularly at higher doses or when taking it on an empty stomach.

To prevent nausea, try taking your supplement with food, or consider taking it at night before you go to bed. Splitting the dose can also help.

Yes, prenatal vitamins can cause nausea, and while folic acid can be a factor, iron is often the primary culprit. Some women find relief by switching to a different brand or formula.

You should seek medical attention if nausea is severe, persistent, or accompanied by other serious symptoms like a rash, difficulty breathing, or swelling, as this could indicate an allergic reaction or overdose.

Besides nausea, other potential side effects include loss of appetite, bloating, gas, stomach cramps, and an unpleasant taste in the mouth.

Yes, an overdose of folic acid can cause a number of side effects, including significant nausea and vomiting. It is important to adhere to the recommended daily dosage.

High doses of folic acid can mask the symptoms of a vitamin B12 deficiency, which can be dangerous as it can lead to serious neurological damage if left untreated.