A typical flaxseed oil dose for a large dog is one to two teaspoons daily, according to Whole Dog Journal. Small toy breeds should receive ¼ to ½ teaspoons of flaxseed oil daily.

Limiting your dog's flaxseed oil dosage is important because the oil is a rich source of fat and calories, says Whole Dog Journal. As with any supplement, start with a small dose and monitor your dog's reaction. Flaxseed oil can be mixed into canned food, broth or any commercial gravy designed for dogs.

Flaxseed oil is safe for dogs and can also act as a source of dietary fiber, explains VCA Animal Hospitals. Though not as concentrated as fish oil, flaxseed oil may treat inflammation and arthritis.