By Rania Gollakner, BS, DVM, MPH

What is bilberry?

Bilberry, also known as the European blueberry, whortleberry, or huckleberry, is a berry related to the blueberry. Bilberry has a high concentration of anthocyanins, which is an antioxidant. Bilberry is used as a dietary supplement to mainly treat eye problems, but it has also been used as an antioxidant to treat cardiovascular conditions, diarrhea, urinary tract infections, diabetes, and other conditions.

New research has suggested that flavonoids found in bilberry may inhibit the formation of hemangiomas (a benign tumor), resulting in a reduction of tumor size by about 50 percent in one human study. These results suggest bilberry extract may hold promise in treating cancerous vascular (blood vessel) tumors in dogs, such as hemangiosarcoma. An anti-neoplastic (i.e., anti-tumor) effect against other cell types has also been demonstrated, due in part to bilberry’s content of anthocyanins.

What is a dietary supplement?

Dietary supplements are substances that can be used to supplement the diet, such as vitamins, minerals, amino acids, herbs, botanicals, enzymes, and probiotics. While many supplements are sold over the counter, they still contain ingredients that have biological effects that should be managed by your veterinarian. Follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

There are differences in how countries regulate supplements. In the United States, these substances are not as vigorously regulated by the FDA as other medications, which means they can be sold without the manufacturer proving their effectiveness, safety, and without a guarantee of consistent or accurately reported ingredients. In Canada, products that have been evaluated for quality, safety, and effectiveness by Health Canada and authorized for sale will have a license number on the label.

How effective is bilberry?

Limited studies in animals have been performed, but there is anecdotal evidence that bilberry may improve any condition that would benefit from antioxidant therapy, such as cancer, cardiovascular disease, inflammation, high blood sugar, vision problems, or infections.

Bilberry is unlikely to be effective for progressive retinal atrophy (PRA or deterioration of the blood vessel and nerve-rich back of the eye) in dogs.

While it has not been proven yet, bilberry may be more beneficial for dogs in the treatment of hemangiosarcoma (blood vessel cancer).

How is bilberry given?

Bilberry is given by mouth in the form of a capsule, tablet, liquid, or powder. Measure liquid doses carefully. It may be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food.

What if I miss giving my pet the supplement?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Studies are limited for this supplement and therefore information regarding side effects is also limited.

Are there any risk factors for this supplement?

Studies are limited for this supplement and therefore information regarding risk factors is also limited. However, no risk factors have been documented to date.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with bilberry: insulin, warfarin or other blood thinners.

Vitamins, herbal therapies, and supplements have the potential to interact with each other, as well as with prescription and over the counter medications. It is important to tell your veterinarian about any medications (including all vitamins, supplements, or herbal therapies) that your pet is taking.

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

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the supplement is helping. Monitor your pet at home for side effects.

How do I store bilberry?

There are many different manufacturers of this supplement, so follow the storage directions on the label.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the supplement, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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