Garlic is indeed toxic to dogs and has an especially hazardous effect on their red blood cells. It takes a rather high or concentrated dose of garlic to have a detrimental effect, according to the American Society for the Prevention of Cruelty to Animals.
Some of the most likely substances to cause toxic results include garlic powder. Dogs that have ingested an excessive amount may exhibit signs of extreme fatigue and urine that is either orange or dark red in color approximately three to five days after their garlic ingestion. An immediate appointment with a veterinarian is a recommended solution for dogs that show such symptoms and may have had access to a high dose of garlic, according to the ASPCA.