What the label lists and what reports show

Folic acid side effects

Folic acid's FDA label lists its adverse reactions in its own words. FAERS holds 247,883 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is fatigue (23,921 reports).

Generic listed

Check it at the source: the folic acid FDA label on DailyMed (effective July 24, 2026, Rising Pharma Holdings, Inc.); the FDA FAERS public dashboard.

What does the label list?

From the label: adverse reactions
Allergic sensitization has been reported following both oral and parenteral administration of folic acid. Folic acid is relatively nontoxic in man. Rare instances of allergic responses to folic acid preparations have been reported and have included erythema, skin rash, itching, general malaise, and respiratory difficulty due to bronchospasm. One patient experienced symptoms suggesting anaphylaxis following injection of the drug. Gastrointestinal side effects, including anorexia, nausea, abdominal distention, flatulence, and a bitter or bad taste, have been reported in patients receiving 15 mg folic acid daily for 1 month. Other side effects reported in patients receiving 15 mg daily include altered sleep patterns, difficulty in concentrating, irritability, overactivity, excitement, mental depression, confusion, and impaired judgment. …

Source: FDA drug label, Rising Pharma Holdings, Inc., effective July 24, 2026 (SPL set 0baa10dd-6d1d-4946-8236-566451132da3), via openFDA; the full label on DailyMed

What do FAERS reports show?

247,883 reports list folic acid among the medicines taken, each a report of something that happened, not proof the medicine caused it; 23,149 are coded as a death and 89,888 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 22 reactions below, 3 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.

Reports received each year

The 25 most reported reactions

Drug Ineffective (a use or a product term, not a reaction)25,264
Fatigue23,921
Pain23,620
Arthralgia19,991
Off Label Use (a use or a product term, not a reaction)18,071
Rheumatoid Arthritis17,937
Nausea (named in the label)16,045
Diarrhoea14,600
Headache14,599
Rash (named in the label)14,022
Dyspnoea13,659
Abdominal Discomfort11,979
Alopecia11,928
Joint Swelling11,794
Condition Aggravated (a use or a product term, not a reaction)11,482
Vomiting11,244
Pneumonia11,218
Pyrexia10,952
Pain In Extremity10,823
Systemic Lupus Erythematosus10,175
Malaise (named in the label)10,170
Dizziness10,145
Nasopharyngitis9,644
Arthropathy9,498
Swelling9,469

Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms

What next?

Folic acid: the full record: label, generics, price, shortages, recalls
Report a side effect to the FDA: MedWatch
Side effects hub: the most reported medicines and reactions