A suspect is in police sights over the deaths of two nursing home patients in the NSW Hunter region.

An 83-year-old woman and an 81-year-old man died in October last year after allegedly being injected with insulin at the Sugarloaf Gardens nursing home in Wallsend, Newcastle.

A third patient, a 91-year-old woman, was also admitted to hospital after suffering the same hypoglycaemia symptoms, but survived.

Homicide detectives are investigating and police say they have a suspect.

"We are happy for people to know that we are looking at them," Newcastle crime manager Graeme Parker told ABC radio.

He said police were working to establish a motive.

"It's complicated and secretive," he said.

"Homicides are generally crimes of passion. We don't believe that's the case in this circumstance."

Source: aap