What are the side effects of taking folate Syrup?

December 11, 2025 •

4 min read

According to the Centers for Disease Control and Prevention (CDC), many studies have found folic acid, the synthetic form of folate, to be safe and effective at recommended doses, yet potential side effects and interactions with other medications should be carefully considered. Folate syrup is generally well-tolerated, but misuse or high doses can lead to adverse health issues.

Quick Summary

Taking folate syrup is generally safe when used correctly, but potential side effects can include nausea, bloating, and loss of appetite, especially with high doses. Excessive intake can dangerously mask an underlying vitamin B12 deficiency, leading to severe neurological damage if untreated. Serious side effects like allergic reactions are rare but require immediate medical attention.

Key Points

Mild Gastrointestinal Issues: Taking folate syrup, especially in higher doses, can cause nausea, bloating, loss of appetite, and stomach cramps.
Masking a B12 Deficiency: Excessive folate intake is a serious risk because it can hide the signs of a vitamin B12 deficiency, potentially leading to irreversible neurological damage if not properly diagnosed.
Adverse Allergic Reactions: Though rare, serious allergic reactions are possible, with symptoms including hives, skin rashes, and difficulty breathing.
Medication Interactions: Folate supplements can interact with other drugs, particularly those for epilepsy like phenytoin, and other medications like methotrexate.
Consult a Doctor: It is crucial to consult a healthcare professional before taking folate syrup to determine the correct dosage and to discuss any pre-existing conditions.
Risk of Overdose: Taking more than the prescribed amount of folate syrup can lead to overdose symptoms such as severe stomach pain and should be addressed immediately.

Folate, or vitamin B9, is a crucial nutrient for many bodily functions, including cell growth, DNA formation, and the creation of red blood cells. It is available as a supplement in various forms, including syrup, which is often used to treat deficiencies. While generally safe, particularly at recommended dosages, it is important to be aware of the potential side effects, especially with higher intake or long-term use. Side effects range from mild gastrointestinal discomfort to more serious issues, including the masking of a vitamin B12 deficiency.

Common Side Effects of Folate Syrup

For most individuals taking the recommended dose of folate syrup, side effects are rare and typically mild. However, some people may experience the following:

Gastrointestinal Distress: This is one of the most frequently reported side effects associated with folate supplementation, particularly with higher doses. Symptoms can include nausea, loss of appetite, bloating, gas, and stomach cramps. Taking the syrup with food can often help mitigate these issues.
Changes in Taste: Some users may experience a bitter or unpleasant taste in their mouth after taking folate syrup.
Irritability and Mood Swings: In rare cases and often associated with higher doses, folate can cause mood changes such as irritability, confusion, or feelings of excitement.
Sleep Problems: Insomnia or general trouble sleeping has been noted as a potential side effect for those taking high doses.

Serious Risks and Considerations

While less common, some side effects are more serious and require careful monitoring and medical consultation. The most critical risk is related to vitamin B12.

The Risk of Masking a Vitamin B12 Deficiency

This is arguably the most significant risk associated with excessive folate intake. High doses of folate can correct the megaloblastic anemia caused by a vitamin B12 deficiency, but they do not address the underlying neurological damage. If the B12 deficiency remains undiagnosed and untreated, it can lead to irreversible nerve damage. Symptoms of this neuropathy include tingling or numbness in the hands and feet. This is why it is crucial for doctors to check B12 levels before prescribing high-dose folate supplementation.

Allergic Reactions

Although rare, severe allergic reactions to folate are possible. Symptoms include hives, itching, rash, wheezing, and swelling of the face, lips, tongue, or throat. Any signs of a serious allergic reaction warrant immediate medical attention.

Impact on Epilepsy and Other Conditions

For individuals with a seizure disorder, high doses of folate supplements may increase the risk of seizures or decrease the effectiveness of certain antiepileptic drugs. Folate can also interact with other medications, such as methotrexate, so it's essential to inform your doctor about all medicines being taken.

Common vs. Serious Side Effects


Feature	Common Side Effects	Serious Side Effects
Symptom Type	Primarily gastrointestinal and mood-related	Neurological damage, severe allergic reaction, increased seizure risk
Likelihood	Rare at recommended doses, increases with higher doses	Very rare, but potentially life-altering
Cause	Generally linked to dosage or individual sensitivity	High doses, pre-existing conditions, or allergic response
Resolution	Often temporary; may resolve by adjusting dosage or timing	Requires immediate medical intervention and diagnosis
Alert Level	Low; often managed at home with simple adjustments	High; requires urgent contact with a healthcare provider

Proper Folate Usage and Overdose

Always follow your doctor's prescribed dosage for folate syrup. Taking more than the recommended amount will not yield better results and significantly increases the risk of side effects, including overdose. Symptoms of an overdose may include severe stomach pain, persistent nausea, and extreme fatigue. In case of a suspected overdose, seek emergency medical help immediately. Excessive alcohol consumption can also interfere with folate absorption and worsen side effects.

Conclusion

Folate syrup is a valuable supplement for treating deficiencies and promoting overall health when used correctly. The key to minimizing side effects is adhering to the prescribed dosage and consulting with a healthcare professional, especially if you have pre-existing conditions or are taking other medications. While common side effects are mild and infrequent, the more serious risks—particularly the masking of a vitamin B12 deficiency—underscore the need for professional guidance. Any signs of an allergic reaction should be treated as a medical emergency. By understanding these potential issues, you can use folate syrup safely and effectively to support your health..

For more information on folate and its role in the body, you can refer to the National Institutes of Health (NIH) fact sheet on folate.

Citations

Drugs.com: Folic Acid: Uses, Dosage, Side Effects, Warnings
Mayo Clinic: Folate (folic acid)
WebMD: Folic Acid (Folate): Uses, Dosage, Effects, Food Sources, and More
1mg: BI-Folate Syrup: View Uses, Side Effects, Price and Substitutes
Healthline: 4 Potential Side Effects of Too Much Folic Acid
Centers for Disease Control and Prevention (CDC): Folic Acid Safety, Interactions, and Health Outcomes
NHS: Side effects of folic acid
Cleveland Clinic: Folic Acid Tablets: Uses & Side Effects

Frequently Asked Questions

Common side effects, particularly with high doses, can include nausea, loss of appetite, bloating, gas, stomach pain, and a bitter taste in the mouth.

Yes, excessive folate intake can be dangerous, primarily by masking an underlying vitamin B12 deficiency, which can cause severe and irreversible nerve damage if left untreated.

A serious allergic reaction to folate can manifest as a skin rash, itching, hives, swelling of the face, lips, tongue, or throat, and difficulty breathing. Seek immediate medical help if these occur.

Yes, high doses of folate can interact with certain medications, including antiepileptic drugs and methotrexate, by reducing their effectiveness. Always inform your doctor of all medications you are taking.

Yes, taking more than the recommended dose can lead to an overdose. Symptoms may include severe stomach pain, persistent nausea, and unusual fatigue. Immediate medical attention is required.

A healthcare provider should check vitamin B12 levels before prescribing high-dose folate supplementation, especially in individuals at risk for a B12 deficiency, to ensure proper diagnosis and treatment.

Yes, the likelihood and severity of side effects, including gastrointestinal issues and mood changes, increase with higher dosages of folate syrup.