Teacup puppies are generally defined as puppies that grow to be no more than 2 to 4 pounds as adults. However, the term "teacup" is not officially recognized, so there is no standard definition.
Toy breeds are a class of dogs that are no more than 11 pounds when fully grown. Most teacup puppies are versions of toy dogs, commonly the Chihuahua, Yorkshire terrier, Pomeranian and Maltese. Others are mixed breed versions of these dogs, sometimes referred to by breeders as "designer dogs." A teacup puppy is often the runt of a toy breed litter, or even a puppy that was born prematurely.
People are attracted to teacup puppies because they maintain puppy-like appearances into adulthood and eat less than larger dogs, which reduces food costs. Unfortunately, the cute looks and lower food expenses associated with teacup puppies come with significant and costly health risks. Some breeders of toy dogs repeatedly breed runts together to intentionally produce tiny dogs. As a result, teacup puppies typically only live to be a few years old and suffer from ailments such as hypoglycemia, fragile bones, immune system deficiencies, seizures, heart problems, collapsing trachea, digestive problems, limb deformities and blindness. Most teacups also suffer from nervousness, so it is not always possible to take them outside.