Folic Acid

Folic acid is the supplemental form of vitamin B9, a nutrient required for one-carbon metabolism and normal cell production. Veterinary supplementation primarily addresses folate deficiency, often associated with intestinal disease or inadequate nutrient availability. Normal folate availability is particularly important in rapidly dividing tissues such as intestinal epithelium and bone marrow.

Group

Vitamin B9 supplement

Mechanism of Action

Folic acid is reduced to tetrahydrofolate derivatives that carry one-carbon units for purine and thymidylate synthesis and amino-acid metabolism. These reactions support DNA synthesis and normal maturation of rapidly dividing cells, including marrow precursors. Replacement of a deficient folate supply restores these metabolic pathways and supports normal erythropoiesis and tissue renewal.

Dose Rates

Cats

Use / stage	Dose	Route	Schedule	Instructions
Folate supplementation	0.2 mg/animal	PO	Every 24 h	Up to 28 days
Folate deficiency with exocrine pancreatic insufficiency	0.4 mg/animal	PO	Every 24 h
Folate support during prolonged high-dose trimethoprim-sulfa	2 mg/animal	PO	Every 24 h	Described during prolonged Nocardia treatment; evaluate folate and cobalamin status.
Folate adjunct for inflammatory bowel disease	0.5–1 mg/animal	PO	Every 24 h	Described with cyanocobalamin 125–250 mcg total SC or IM weekly for 4–6 weeks; correct the underlying enteropathy.

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Folate supplementation	Reference only	PO	Every 24 h	Up to 28 days; Dogs under 20 kg: 200 mcg once daily; dogs at least 20 kg: 400 mcg once daily, for 4 weeks. These are fixed size-dependent amounts, not a continuous mg/kg range.
Folate deficiency with inflammatory bowel disease	5 mg/animal	PO	Every 24 h	Listed duration 1–6 months with cyanocobalamin 750 mcg total parenterally monthly; the cobalamin injection route is not specified.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Folate support during antifolate treatment	20–40 mg/animal	PO	Every 24 h	Described during prolonged trimethoprim/pyrimethamine or similar antifolate treatment, especially in pregnant mares.

Indications

Treatment of documented folate deficiency in dogs, cats, horses or other veterinary patients.
Nutritional replacement in selected patients with hypofolatemia associated with chronic small-intestinal disease, malabsorption or inadequate intake.
Treatment of selected folate-deficiency-associated megaloblastic changes or impaired erythropoiesis.

Contraindications

Hypersensitivity

Interactions

Folate antagonists such as methotrexate require a separate treatment-specific rescue plan; folic acid is not interchangeable with folinic acid.
Chloramphenicol may delay hematologic response.
Phenytoin exposure and seizure control may change with folate supplementation.
Sulfasalazine, barbiturates, nitrofurantoin and primidone may increase folate deficiency risk.

Adverse effects

Usually well tolerated at supplementation doses

Toxicity

Large or inappropriate supplementation does not correct the underlying cause of anemia or intestinal disease.

Preparations

Preparation	Form	Strength	Route
Folic acid tablets 1 mg Single-active tablet. No equal-dose physical divisions verified.	Tablet	1 mg / tablet	PO
Folic acid tablets 0.4 mg	Tablet	0.4 mg / tablet	PO
Folic acid tablets 0.8 mg	Tablet	0.8 mg / tablet	PO

Monitoring and Administration

Assess cobalamin concurrently when intestinal disease or malabsorption is suspected.

The benefit of correcting an isolated low folate concentration has not been clearly demonstrated; treat the underlying proximal small intestinal disorder.

Severe folate deficiency has been treated with 0.5–2 mg total once daily for one month; that particular description does not state the administration route, so it is not used for automatic route-specific calculation.

Measure folate and cobalamin before therapeutic supplementation and follow clinical signs and abnormal CBC results. Protect blood samples from heat and bright light; hemolysis can falsely increase serum folate.

Folic acid is not folinic acid or L-methylfolate. Avoid multivitamin products that would overdose vitamins A or D when supplying the intended folate amount. Store protected from light and moisture at 15–30°C.