The Napier court case involved a couple who had been married about 23 years but who were not from or in Hawke's Bay.
According to a police summary, the woman had been in hospital last year and was recovering at home monitored by her doctor.
Further tests were ordered amid suspicion the woman had had an adverse reaction to antibiotics she had been prescribed.
The summary said the couple then made a pact to commit suicide together, and prepared several typed and written documents detailing their plan and their affairs, and addressed them to police, a Coroner, and their respective children.
The man also placed a letter outside a neighbour's address, where it was found the next morning, leading to police being called and finding the couple in their bed.
The woman was dead, but the man was still alive.
The man, who had no previous criminal record, declined to comment to police, the summary said, but in court he pleaded guilty to a charge which the maximum penalty is five years' jail.
He has however been remanded at large, meaning there is no bail nor conditions of his remand other than to appear for sentence on October 18.
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
OR IF YOU NEED TO TALK TO SOMEONE ELSE:
• 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP) (available 24/7)
• https://www.lifeline.org.nz/services/suicide-crisis-helpline
• YOUTHLINE: 0800 376 633
• NEED TO TALK? Free call or text 1737 (available 24/7)
• KIDSLINE: 0800 543 754 (available 24/7)
• WHATSUP: 0800 942 8787 (1pm to 11pm)
• DEPRESSION HELPLINE: 0800 111 757 or TEXT 4202