Rebecca Leighton appeared at Manchester Magistrates Court where she was accused of three counts of criminal damage with intent to endanger life and three counts of criminal damage being reckless as to whether life was being endangered.
She also faced a charge of stealing medicine from Stepping Hill Hospital in Stockport, Greater Manchester.
Leighton was arrested at her flat on Wednesday by detectives investigating the contamination of saline solution at Stepping Hill, where she worked.
The alarm was raised at the hospital in Stockport when a higher than normal number of patients were reported to have “unexplained” low blood sugar levels.
Derek Weaver, 83, from Stockport, died on 22 July after suffering a hypoglycaemic episode on 11 July. a day after he was admitted from his interim care home with breathing problems.
Multiple sclerosis sufferer Tracey Arden, 44, of Heaviley, died on 7 July, and retired photographer Arnold Lancaster, 71, of Romiley, died on 11 July.
George Keep, 84, of Cheadle, died on 14 July after being admitted to the hospital with a broken hip, while on the same day 84-year-old Vera Pearson also died.
A man in his 40s linked with the investigation remains “very poorly” in a critical care unit at Stepping Hill.