Many dogs may be in need of pet medication because they are left on their own for long periods of time in cramped conditions while their owners are out at work.
According to research by Churchill Insurance, two-thirds of dogs are left on their own for four hours or more in the kitchen during the day, equating to around a million animals.
Pete Bishenden, a spokesman for Churchill Pet Insurance, said: "The significant number of large dogs that are being kept in cramped conditions for hours at a time is of great concern.
"Before they take on a pet, potential owners should ensure they have sufficient space to keep a dog, as well as being able to dedicate a considerable amount of time to looking after it."
Findings reveal that 13 per cent of owners do not walk their dogs as often as they should. The same proportion of owners also said their dogs are not given enough exercise if the weather is poor.
Fifteen per cent said they wished they could spend more time caring for their dogs.