The 43-year-old, from Reading, was arrested by Thames Valley Police, which is investigating the unexplained death of Gerald Jones.
Mr Jones, 51, died suddenly at an address in Wrenswood Close, Reading, on 19 June.
Police arrested the woman after receiving information following a post-mortem examination.
She was later released on bail until 30 January.
A woman has been arrested on suspicion of murder after the death of a man in June.