An elephant who's been at the Denver Zoo since 1961 is in poor health.Zookeepers say Mimi has begun refusing food and medication.Because the next diagnostic tests would require more invasive measures that would likely not provide new information and could put her health at greater risk, zookeepers told 7NEWS they have decided against the tests.Born in India, Mimi's birth date is not known. However she is believed to be at least 53 years old, making her one the oldest elephants in North American zoos."Although we will continue to offer her the best of care and hope she rebounds, the time has come to allow her to live her remaining time with the dignity and respect she so richly deserves," said Denver Zoo President/CEO Craig Piper. "Mimi has good days and bad days and we have no way of knowing how much time she has left. However, no matter how much we wish, nothing will turn back time and give her the health she enjoyed in her youth.""We are going to focus on making Mimi completely comfortable while we monitor her quality of life," says Denver Zoo COO Kyle Burks.Zookeepers are letting Mimi decide where in the exhibit she is most comfortable. Currently, her favorite area is a private outdoor yard behind the scenes at Toyota Elephant Passage and some of the indoor bedrooms, officials said. Unfortunately, she cannot be seen by zoo guests in these areas.Zookeepers are providing Mimi with an electrolyte solution to keep her hydrated as well as numerous food options, hoping to encourage her to eat.The name Mimi came from the protagonist in the musical, Sail Away. At barely more than four-feet-tall, she was described by one newspaper in 1961 as "so lovable 'you could take her right into your home.'"