Who Cannot Take Folate? High-Risk Groups and Medical Considerations

December 29, 2025 •

4 min read

Approximately 1 in 20 people over the age of 60 may have a vitamin B12 deficiency, a condition that poses a significant risk for those considering folate supplementation. While essential for most, there are specific medical conditions, genetic factors, and medication interactions that mean some people cannot take folate or should do so with extreme caution under medical supervision.

Quick Summary

Certain individuals with medical conditions like undiagnosed vitamin B12 deficiency, specific cancers, or epilepsy must avoid or be cautious with folate supplementation. High doses can mask serious neurological symptoms or interfere with critical medications, necessitating professional medical advice before use.

Key Points

Undiagnosed Anemia: Taking folate with an undiagnosed B12 deficiency can mask megaloblastic anemia symptoms while irreversible neurological damage progresses.
Cancer and Pre-cancerous Growths: Individuals with certain cancers should avoid high-dose folic acid, as it may accelerate tumor growth or interfere with chemotherapy.
Epilepsy: High doses of folate can worsen seizures and reduce the efficacy of anticonvulsant medications.
Medication Interference: Folate interacts with several drugs, including those for epilepsy, chemotherapy (e.g., methotrexate), and some antibiotics.
MTHFR Gene Variation: People with MTHFR mutations may process folate differently; discussing appropriate forms with a healthcare provider is recommended.
Kidney or Liver Disease: Conditions affecting these organs can impact folate metabolism and may require alternative approaches under a doctor's care.

Undiagnosed Vitamin B12 Deficiency and Pernicious Anemia

One of the most critical reasons certain people cannot take folate is the presence of an undiagnosed vitamin B12 deficiency, including pernicious anemia. A vitamin B12 deficiency often leads to a type of megaloblastic anemia, where red blood cells are abnormally large. This is also a symptom of folate deficiency. Taking high doses of folic acid can correct the blood-related symptoms of megaloblastic anemia caused by a B12 shortage, but it does nothing to address the progressive, and potentially irreversible, neurological damage that can result from the deficiency. By masking the anemia, folate can prevent the timely diagnosis and proper treatment of the underlying B12 issue, leading to severe and lasting nerve damage. For this reason, it is imperative to have any anemia diagnosed and the cause confirmed before starting folate supplementation.

Symptoms of B12 Deficiency to Watch For

Extreme tiredness and lack of energy
Tingling and numbness in the hands and feet
Problems with memory and concentration
Psychological problems, such as depression or anxiety
A sore and red tongue or mouth ulcers

Cancer and Preneoplastic Lesions

For individuals with a history of cancer, preneoplastic (pre-cancerous) growths, or an active diagnosis, high-dose folate supplementation can be a double-edged sword. Research indicates that while adequate folate can help protect against the development of certain cancers, high doses may provide fuel for cancer cells, potentially accelerating tumor growth or recurrence. This is because folate is essential for DNA synthesis and cell division, processes that cancer cells rely on for rapid proliferation. Furthermore, some chemotherapy drugs, known as antifolates (e.g., methotrexate), work by blocking folate-related processes. Supplemental folate can interfere with the effectiveness of these treatments, making them less potent against cancer cells. Anyone with a cancer diagnosis or a history of the disease should discuss their folate intake with their oncologist before taking any supplements.

Epilepsy and Seizure Disorders

Patients with epilepsy or other seizure disorders, particularly those taking certain anticonvulsant medications, should be cautious with folate supplements. High doses of folate have been shown to potentially worsen seizures in some individuals. Folate can also interact with antiepileptic drugs, such as phenobarbital, phenytoin, and primidone, by affecting how the body processes the medication, which can decrease its effectiveness and increase the risk of seizures.

Medication Interactions

Folate can interact with a variety of other medicines, potentially reducing their effectiveness or increasing side effects. It is crucial to inform your doctor about all medications you are taking before beginning a folate supplement. Some known drug interactions include:

Methotrexate: Used for cancer, rheumatoid arthritis, and psoriasis. Folate can reduce its effectiveness.
Anticonvulsants: Including phenobarbital, phenytoin, and primidone, used for seizures.
Certain Antibiotics: Tetracycline can cause false low folate levels. Sulfasalazine, used for inflammatory bowel disease, can affect folate absorption.
Chemotherapy Drugs: Including fluorouracil and capecitabine.
Zinc: High-dose folic acid can hinder zinc absorption.

Other Specific Health Conditions

Certain other health circumstances and conditions also necessitate caution or avoidance of folate supplementation:

Hereditary Folate Malabsorption: A rare genetic disorder prevents the body from absorbing folate from food, leading to a deficiency despite adequate dietary intake. Management requires specific medical treatment rather than standard supplements.
Kidney or Liver Disease: Individuals with liver disease or those on kidney dialysis may require different supplementation protocols and should consult their healthcare provider.
Post-Angioplasty: People recovering from angioplasty procedures to widen narrowed arteries are advised to avoid folate.

Comparison of Groups Who Cannot Take Folate


Condition / Group	Primary Reason for Caution	Associated Risks	Management
Undiagnosed B12 Deficiency	High-dose folate can mask megaloblastic anemia, a symptom common to both B12 and folate deficiency.	Allows the progression of irreversible neurological damage from B12 deficiency.	Diagnosis of the specific anemia cause is required.
Certain Cancers	Folate is essential for cell division, and high levels may accelerate the growth of existing cancer cells.	Interference with antifolate chemotherapy medications; increased risk of recurrence or progression.	Close consultation with an oncologist is mandatory.
Epilepsy	High doses can potentially trigger or worsen seizures in some individuals.	Reduced effectiveness of certain anticonvulsant drugs like phenytoin and phenobarbital.	Discuss folate intake with a neurologist and monitor drug levels.
Medication Interactions	Folate can directly interfere with the action or metabolism of certain drugs.	Decreased effectiveness of epilepsy drugs or chemotherapy agents; reduced absorption of other nutrients.	Review all medications with a healthcare provider before supplementing.
Genetic MTHFR Variation	Impaired ability to convert synthetic folic acid into its active form.	Potential for unmetabolized folic acid to accumulate; may require methylated folate instead.	Not an absolute contraindication for folate, but warrants discussing different forms with a doctor.

Conclusion: The Importance of Professional Guidance

While folate is an indispensable nutrient for many physiological processes, particularly for preventing birth defects during pregnancy, it is not universally safe for everyone. The potential for high doses of folic acid to obscure a vitamin B12 deficiency and cause lasting neurological damage is a serious concern that underscores the need for a proper medical diagnosis. Furthermore, its complex interactions with medications and potential influence on cancer progression mean supplementation decisions should never be taken lightly. If you have any of the medical conditions or are on any of the medications discussed, it is absolutely essential to speak with your healthcare provider before considering a folate supplement. A thorough understanding of your personal health history is the only way to ensure folate supplementation is both safe and beneficial for you.

Visit WebMD for a detailed list of drug interactions with folic acid.

Frequently Asked Questions

The primary risk is that high doses of folate can correct the blood abnormalities (megaloblastic anemia) caused by a B12 deficiency. This can hide the deficiency, allowing irreversible neurological damage to progress unnoticed.

For cancer patients, high-dose folic acid is a concern because it is necessary for cell growth. In some cases, it can promote the growth or spread of existing cancer cells and may interfere with the effectiveness of certain chemotherapy drugs.

Yes, folate can interact with several anticonvulsant medications, including phenytoin and phenobarbital. High doses can potentially decrease the effectiveness of these drugs and increase the risk of seizures.

Yes. Natural folate found in food is metabolized differently than synthetic folic acid. Some individuals with genetic variations, like MTHFR, have a reduced ability to convert folic acid and may benefit from alternative forms.

Signs include extreme fatigue, lack of energy, tingling sensations, a sore tongue, mouth ulcers, and problems with memory or psychological issues like depression.

The MTHFR gene provides instructions for an enzyme that converts folate into its active form. A common mutation can reduce this enzyme's effectiveness, potentially requiring an active folate supplement like methylfolate, although standard doses are often processed sufficiently.

You should not stop taking any supplement without consulting a healthcare provider, especially if you have a pre-existing medical condition. A doctor can help determine the right course of action based on your specific health profile.