The record holder for the tallest dog ever is a Great Dane called Zeus (died September 2014; aged 5), who measured 111.8 cm (44.0 in) from paw to shoulder. The tallest living dog is another Dane named Freddy, measuring 103.5 cm (40.7 in).
Great Danes, like most giant dogs, have a fairly slow metabolism. This results in less energy and less food consumption per pound of dog than in small breeds. They have some health problems that are common to large breeds, including bloat (gastric dilatation volvulus). To avoid bloat, a rest period of 40 minutes to one hour after meals is recommended before exercise. Their average lifespan is 6 to 8 years; however, some Great Danes have been known to reach 10 years of age or more. Like many larger breeds, Great Danes are at particular risk for hip dysplasia.
Dilated cardiomyopathy and many congenital heart diseases are also commonly found in the Great Dane, leading to its nickname: the heartbreak breed, in conjunction with its shorter lifespan. Great Danes also may carry the merle gene, which is part of the genetic makeup that creates the harlequin coloring. The merle gene is an incomplete dominant, meaning only one copy of the gene is needed to show the merle coloring; two merle genes produce excessive white markings and many health issues such as deafness, blindness, or other debilitating ocular issues. Great Danes can also develop wobbler disease, a condition affecting the vertebral column. Since these dogs do grow at a rapid rate, the bones in their vertebrae can push up against the spinal cord and cause weakness in the legs. This can be treated with surgery or may heal itself over time.
In Austria and Germany the Molossian hound, the Suliot dog and other imports from Greece were used in the 18th century to increase the stature of the boarhounds.