Adult teacup Yorkies typically weigh 1 to 3 pounds and are normally less than 4 pounds. American Kennel Club guidelines for breeding full-size Yorkshire Terriers, by contrast, mandate a minimum weight of 4 pounds and a maximum of 7.

Teacup Yorkies can weigh a lot less, however, with the smallest on record weighing 4 ounces.

Despite their popularity, there are significant welfare concerns associated with the breeding of "teacup" dogs. The word actually refers to a genetic defect that often leads to health problems such as hypoglycemia, according to Midwest Animal ResQ. Unethical breeders have also been criticized for separating alleged "teacup" puppies from their mothers too early in life.