Teacup dogs are unusually small versions of standard small or toy breeds and usually weigh no more than 4 pounds at maturity. Some teacup dogs are naturally occurring runts in normal litters, but others are the result of unscrupulous breeding practices and have a high incidence of health problems.
Teacup dogs often result from breeding runt puppies to one another. These pregnancies are risky for the mothers and often result in maternal death. Another unscrupulous practice is marketing puppies born prematurely as teacups, a practice that predisposes the dogs to respiratory disorders, organ failure and hypoglycemia. Because of their tiny size, even otherwise healthy teacup dogs are prone to broken bones from even small falls and jumps.