Ascorbic Acid (Vitamin C)

What is ascorbic acid?

Ascorbic acid (also known as Vitamin C) is an essential vitamin needed to maintain good nutrition and a healthy immune system. Some animals, such as guinea pigs, need ascorbic acid added to their diet as they cannot produce it on their own. It is used to treat scurvy in guinea pigs, as an antioxidant for certain toxins that cause methemoglobinemia in cats and dogs, and as a stool softener in rabbits.

The U.S. Food and Drug Administration (FDA) does not review non-drug health products (e.g., herbals, nutraceuticals, shampoos, and other supplements) for safety or effectiveness before they are sold to the public. Manufacturers of non-drug health products must ensure their products are safe and labeled accurately. The FDA requires that these non-pharmaceuticals contain a disclaimer that says, “This product is not intended to diagnose, treat, cure or prevent any disease.”

Health Canada licenses “veterinary health products” after reviewing safety, efficacy, and manufacturing information provided by the manufacturer. These products are not tested by Health Canada. Your veterinarian is the best source of information about the safety of non-drug health products in pets. Just because a product is natural does not mean it is safe. All medicines and medicinal plants are potentially toxic if used inappropriately or given at high doses. Supplements can also have side effects, like pharmaceuticals. Few supplements and herbs have been subjected to rigorous scientific trials to determine their efficacy. Although the information in this handout may be helpful, it also may be incomplete and may not represent the full range of effects the supplement could have on your pet.

How do I give my pet ascorbic acid?

• Ascorbic acid comes in tablet, capsule, liquid, powder, and injectable forms. Some forms are available over the counter (OTC).
• Tablets, capsules, liquids, and powders are given orally (by mouth).
• Injectable forms are given subcutaneously (under the skin) or intramuscularly (into the muscle).
• This medication can be given with or without food.
• Measure the liquid forms of this medication very carefully.
• Give this medication exactly as prescribed and directed by your veterinarian.

This medication should start to take effect in 1–2 hours, though outward effects will not be noticeable.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember. However, if it is almost time for the next scheduled dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects from ascorbic acid?

Ascorbic acid may cause the following side effects:

• Diarrhea

Serious adverse reactions may occur. If any of the following signs develop, stop giving ascorbic acid and contact your veterinarian immediately:

• Signs of kidney or urinary stones (e.g., straining to urinate, no urine production, pain, blood in urine)

Drug sensitivities can develop over time with repeated exposure. Your pet may have no reaction after the first few doses, but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment. 

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, though effects may last longer in pets with kidney and/or liver disease.

Are there any risk factors for this medication?

DO NOT USE ascorbic acid in:

• Dogs with copper toxicosis or copper storage disease

USE WITH CAUTION in animals that:

• Have kidney and/or bladder stones
• Have diabetes mellitus and whose urine glucose levels are being monitored

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with ascorbic acid:

• Aluminum hydroxide
• Aminoglycosides
• Copper or copper-containing supplements
• Cyclosporine
• Deferoxamine
• Erythromycin
• Estrogens
• Iron salts
• Quinidine

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is there any monitoring that needs to be done with this medication?

• Your veterinarian will let you know when and how they want to reassess your pet to ensure the supplement is working and not causing side effects.
• At home, monitor for any abnormal changes. If any occur, discontinue the medication and contact your veterinarian.

How do I store ascorbic acid?

• Protect from air and light.
• Follow specific product label directions.
• Keep medication out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet’s weight and symptoms.