Folic Acid
Pteroylglutamic acid
Also known as: Folvite · Deplin · Folate · Folacin · Vitamin B9 · Acidum folicum · Pteroylglutamic acid · Pteroylmonoglutamic acid · Vitamin B11
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Severe folate deficiency | 0.5-2 mg (total dose) PO once daily | PO | q24h | 1 month | 🌎 NA |
| Folate and cobalamin deficiency secondary to inflammatory bowel disease | 5 mg (total dose) PO once daily | PO | q24h | 1-6 months | 🌎 NA |
- Folate and cobalamin deficiency secondary to inflammatory bowel disease: Given with cyanocobalamin 750 micrograms parenterally once per month.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Severe folate deficiency | 0.5-2 mg (total dose) PO once daily | PO | q24h | 1 month | 🌎 NA |
| Folate deficiency secondary to exocrine pancreatic insufficiency | 400 micrograms (0.4 mg) PO once daily | PO | q24h | — | 🌎 NA |
| Long-term use of high dose trimethoprim/sulfa (for treating Nocardia) | 2 mg (total dose) PO once daily | PO | q24h | — | 🌎 NA |
| Adjunctive therapy in cats with inflammatory bowel disease | 0.5-1 mg PO q24h (once daily) | PO | q24h | 4-6 weeks | 🌎 NA |
- Adjunctive therapy in cats with inflammatory bowel disease: Given with cobalamin at 125-250 micrograms SC or IM once a week.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Prolonged therapy with antifolate medications (e.g., trimethoprim, pyrimethamine) | 20-40 mg (total dose) PO per day | PO | q24h | — | 🌎 NA |
- Prolonged therapy with antifolate medications (e.g., trimethoprim, pyrimethamine): Pregnant mares should routinely receive folic acid supplementation during treatment with antifolates.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Folic acid (Vitamin B9) is a vital water-soluble vitamin essential for nucleoprotein synthesis and normal erythropoiesis (red blood cell production).
In veterinary medicine, it is primarily used to treat folate deficiencies, which frequently arise secondary to gastrointestinal disorders.
Clinical Pearls & Diagnostic Utility:
- Absorption Site: Folate is absorbed exclusively in the proximal small intestine, whereas cobalamin (Vitamin B12) is absorbed in the distal small intestine.
- Diagnostic Indicator: Measuring serum folate and cobalamin helps localize intestinal disease. Low folate suggests proximal small intestinal disease.
- Bacterial Overgrowth: Dogs with Exocrine Pancreatic Insufficiency (EPI) or Small Intestinal Bacterial Overgrowth (SIBO) often have increased serum folate because enteric bacteria synthesize folate.
- Antifolate Rescue: It is also used to prevent or treat deficiencies caused by the chronic administration of dihydrofolate reductase inhibitors (e.g., trimethoprim, pyrimethamine).
Mechanism of action
Folic acid is a precursor that must be enzymatically reduced to become biologically active.
Mechanism Pathway: Folic Acid → reduced by dihydrofolate reductase (DHFR) → Tetrahydrofolate (THF / 5-methyltetrahydrofolate).
- THF acts as a crucial coenzyme and methyl donor in the synthesis of purine and pyrimidine nucleotides.
- This pathway is absolutely necessary for DNA synthesis, cellular division, and the maintenance of normal erythropoiesis.
- Drugs like trimethoprim and methotrexate competitively inhibit DHFR, blocking this pathway and potentially causing megaloblastic anemia or leukopenia, which is why folic acid supplementation is used as a rescue therapy.
Safety & warnings
Contraindications
- Known intolerance or hypersensitivity to folic acid
- Undiagnosed anemias (folic acid therapy may mask the hematologic signs of pernicious anemia/cobalamin deficiency while neurologic damage progresses)
Adverse effects
- Hypersensitivity reactions (rare)
- Gastrointestinal effects (rare)
- CNS effects such as difficulty sleeping, excitement, or confusion (seen only at very high oral doses in humans, e.g., 15 mg/day)
Precautions
Important: Do not administer therapeutic doses of folic acid to dogs with enteropathies until baseline serum folate and cobalamin levels have been determined, as dogs may have increased, normal, or decreased folate levels depending on the specific disease process (e.g., bacterial overgrowth vs. malabsorption).
- Prolonged folic acid supplementation can potentially decrease serum cobalamin (B-12) levels.
- Folic acid is considered very safe during pregnancy (FDA Category A) and lactation. Requirements may actually increase in lactating animals.
Drug interactions
May delay the hematologic response to folic acid.
Inhibits dihydrofolate reductase; interferes with folic acid utilization.
Inhibits dihydrofolate reductase; interferes with folic acid utilization.
Inhibits dihydrofolate reductase; interferes with folic acid utilization.
Folic acid may decrease serum phenytoin levels, potentially requiring a dosage increase; increased seizure frequency can occur.
May increase the risk for folate deficiency.
May increase the risk for folate deficiency.
May increase the risk for folate deficiency.
May increase the risk for folate deficiency.
Monitoring
- Serum folate and cobalamin levels (before and after treatment)
- Clinical signs associated with deficiency (e.g., chronic diarrhea, weight loss)
- CBC (baseline and ongoing if abnormal, to monitor for anemia)
Pharmacokinetics
Absorption
Primarily absorbed in the proximal small intestine via carrier-mediated diffusion. Synthetic folic acid is nearly completely absorbed after oral administration, while folate in foodstuffs is about 50% bioavailable.
Distribution
Distributed widely throughout the body and stored in the liver. Erythrocyte and CSF levels can be significantly higher than serum levels. Undergoes enterohepatic recirculation.
Metabolism
Converted to its active form, tetrahydrofolic acid, principally in the liver and plasma.
Elimination
Excreted primarily in the urine either as metabolites or unchanged drug (when administered in excess of body requirements).
Overdose
Folic acid is relatively non-toxic.
If an inadvertent overdose occurs, no specific treatment should be required. Excess drug is rapidly metabolized or excreted unchanged in the urine.
Available products
Formulations
- Tablets
- Injection
Veterinary
- None as sole ingredient products. (Available in various multivitamin combinations)
Human-labeled
- Folic Acid Tablets: 0.4 mg, 0.8 mg (OTC); 1 mg, 7.5 mg, 15 mg (Rx)
- Deplin® (Pamlab)
- Folic Acid Injection: 5 mg/mL in 10 mL vials (Folvite®, generic) (Rx)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store tablets in well-closed containers below 40°C (104°F), preferably between 15-30°C; protect from light and moisture. Store injection protected from light below 40°C (104°F); do not freeze.
Client information
- Purpose: Folic acid is a B-vitamin used to treat deficiencies often caused by chronic intestinal diseases, pancreatic issues, or long-term use of certain antibiotics.
- Safety: It is a very safe supplement. Because it is water-soluble, the body easily eliminates any excess in the urine.
- Administration: Can be given with or without food. Follow your veterinarian's instructions carefully.
- Long-term Care: If your pet has chronic intestinal disease or pancreatic insufficiency, lifelong monitoring of vitamin levels and periodic replacement therapy may be required to keep them healthy.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.