Ascorbic Acid (Vitamin C)

Ascorbic acid is vitamin C, a water-soluble nutrient required for connective-tissue maintenance and several metabolic reactions. Guinea pigs and certain other species require dietary vitamin C because they cannot synthesize adequate amounts. Dogs, cats and most common domestic mammals normally synthesize their own supply, so routine supplementation is not automatically beneficial.

Its clearest veterinary role is prevention or correction of deficiency in susceptible species. Historical urinary acidification and antioxidant applications have a less secure evidence base than nutritional replacement.

Group

Vitamin supplement

Mechanism of Action

Ascorbate acts as an electron donor and maintains metal cofactors in reduced states needed by several enzymes. In collagen synthesis, it supports hydroxylation reactions necessary for stable connective tissue. Deficiency therefore impairs tissue integrity, wound repair and normal vascular support, producing the clinical manifestations of scurvy.

It also participates in redox reactions and metabolic processes involving compounds such as catecholamines and carnitine. Its antioxidant action reflects reversible donation of electrons and regeneration through cellular antioxidant systems; this biochemical activity does not establish improved outcomes in every oxidative disease.

Ascorbic acid has been used to lower urinary pH, but the response is inconsistent and formulation-dependent. Sodium ascorbate does not provide the same acidifying load. Correcting a genuine deficiency is mechanistically different from giving additional vitamin to an animal that already synthesizes adequate amounts.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Dietary supplementation	100–500 mg/animal	PO	Every 24 h
Urinary acidification	100 mg/animal	PO	Every 8 h
Injectable supplementation	250–2500 mg/animal	IM, IV		Listed as 1–10 mL of 250 mg/mL sodium ascorbate according to animal size; no size bands or acid-equivalent basis are specified.
Oxidative stress adjunct	500–1000 mg/animal	PO	Every 24 h

Cats

Use / stage	Dose	Route	Schedule	Instructions
Dietary supplementation	100–500 mg/animal	PO	Every 24 h
Urinary acidification	100 mg/animal	PO	Every 8 h
Injectable supplementation	250–2500 mg/animal	IM, IV		Listed as 1–10 mL of 250 mg/mL sodium ascorbate according to animal size; no size bands or acid-equivalent basis are specified.
Oxidative stress adjunct	125 mg/animal	PO	Every 12 h
Toxic methemoglobinemia adjunct	30 mg/kg	PO	Every 6 h	Adjunct to oxygen and acetylcysteine; does not replace acetylcysteine for acetaminophen poisoning.
Feline infectious peritonitis - historical adjunct	125 mg/animal	PO	Every 12 h	Historical supplementation only; efficacy against FIP is not established and this is not antiviral treatment.

Guinea pigs

Use / stage	Dose	Route	Schedule	Instructions
Vitamin C deficiency	16 mg/kg	IM		Twice weekly. Exact spacing is not given and must not be represented as a uniform 84-hour interval; injection ingredient basis requires product matching.
Scurvy during pregnancy	30 mg/kg	PO		Oral alternative; parenteral route and repeat interval are not specified.
Scurvy treatment	10 mg/kg	PO	Every 24 h	Oral treatment with supportive care; injection is described only when needed without specifying injection route. Typical improvement within a week.
Scurvy - 50 mg/kg alternative	50 mg/kg	PO, IM, SC		Repeat interval is not specified; match injection ingredient basis.
Scurvy prevention - weight-based listing	10–30 mg/kg	PO, SC, IM		Repeat interval is not explicit. Oral intake is preferred for routine nutritional prevention.
Scurvy prevention - dietary maintenance	15 mg/animal	PO	Every 24 h	Daily maintenance requirement following recovery; nutritional needs vary with patient condition.

Rabbit

Use / stage	Dose	Route	Schedule	Instructions
Soft stools - adjunct	100 mg/kg	PO	Every 12 h	Supportive adjunct; investigate the underlying cause.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Post-exercise replacement	20 g/animal	PO	Every 24 h
Oxidative erythrocyte injury adjunct	10–20 g/animal	PO	Every 24 h	Adjunct for conditions such as red-maple toxicity.
Oxidative erythrocyte injury adjunct	30–50 mg/kg	IV	Every 12 h	Dilute in 5–10 L compatible crystalloid; match ascorbic-acid-equivalent injectable strength.
Foal perinatal asphyxia adjunct	100 mg/kg	IV	Every 24 h	Foals; supportive adjunct, not a stand-alone treatment.
Urinary acidification - high historical amount	1–2 g/kg	PO	Every 24 h	Unusually high historical amount; efficacy is uncertain and this should not be substituted for the much lower fixed supplementation amount.

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Vitamin C-responsive calf dermatitis	3 g/animal	SC	Once	One administration, with a possible second treatment; repeat timing is not specified.

Indications

Prevention and treatment of vitamin C deficiency or scurvy in guinea pigs and other species with an established dietary requirement.
Supplementation for inadequate dietary intake or an identified nutritional need.
Historical urinary acidification in small animals; efficacy is uncertain.
Selected antioxidant adjunctive applications; clinical benefit beyond correction of deficiency is not established consistently.

Contraindications

High doses may increase oxalate urolith risk.
Avoid in copper-associated hepatopathy because oxidative hepatic injury may worsen.
Use high doses cautiously in diabetes or urolith-prone patients.

Interactions

Urine acidification may reduce urinary aminoglycoside/erythromycin activity and increase quinidine elimination.
Enhances iron absorption; with deferoxamine it may increase tissue iron toxicity, especially in cardiac disease.

Adverse effects

Possible oxalate urolith risk at high exposure.

Toxicity

Very large doses can cause diarrhea and increase urolith risk. Maintain hydration and monitor renal and gastrointestinal signs.

Preparations

Preparation	Form	Strength	Route
Sodium ascorbate injection 250 mg/mL Amount is sodium ascorbate; no conversion to ascorbic acid is implied.	Injection	250 mg / mL	IM, IV
Xon CE ascorbic acid 500 mg tablet	Tablet	500 mg / tablet	PO
Ascorbic acid 250 mg tablet	Tablet	250 mg / tablet	PO
Ascorbic acid 1000 mg tablet	Tablet	1000 mg / tablet	PO
Ascorbic acid 1500 mg tablet	Tablet	1500 mg / tablet	PO
Ascorbic acid 100 mg/mL oral liquid	Oral Liquid	100 mg / mL	PO
Ascorbic acid injection 500 mg/mL Ascorbic-acid ingredient basis; do not equate with sodium-ascorbate mass.	Injection	500 mg / mL	IV

Monitoring and Administration

Routine supplementation is generally unnecessary with a balanced diet in animals capable of synthesis. Increasing oral dose does not produce proportionate blood-level increases.

Protect from air and light because oxidation causes darkening and decomposition. Injectable vials may develop pressure; refrigeration can reduce this.

Sodium ascorbate injection is described at 250 mg/mL. Without an explicit ascorbic-acid equivalence, it must not be converted using an ascorbic-acid ingredient basis. Large-animal supplementation described without a named species is 1–10 mL IM or IV daily as needed, or 1–2 g PO daily; it is not assigned to guessed species.

Large-animal injectable listing uses the described 250 mg/mL product: 1–10 mL (250–2500 mg sodium ascorbate) IM or IV, repeated daily as needed. Oral listing is 1–2 g daily; no particular large-animal species is identified.

Sodium ascorbate does not acidify urine. Efficacy of ascorbic acid for urinary acidification is uncertain. High doses may cause false-negative urine glucose and stool occult-blood tests, or lower measured serum bilirubin; tell the laboratory about treatment.

Guinea-pig alternatives include 25–50 mg per animal parenterally daily until improvement, but no injection route is specified. Water supplementation uses 200 mg per litre dechlorinated water; actual intake and vitamin degradation affect delivery.