hard of hearing

  If you are hard of hearing, you can't hear very well.

 "You'll have to speak louder to Mr. Jones.  He's a bit hard of hearing."

go under the knife

  If a person goes under the knife, they have surgery.

  "I'm not worried about the anaesthetic.  I've been under the knife several times."

in the land of the living

  This is a humorous way of saying that someone is still alive.

  "Hi there! It's good to see you're still in the land of the living!"

on one's last legs

  If you are on your last legs, you are in a very weak condition or about to die.

  "I was so sick that I felt as though I was on my last legs!"

like death warmed up

  If you look or feel like death warmed up, you look or feel very ill or tired.

  "My boss told me to go home. He said I looked like death warmed up."

living on borrowed time

  This expression refers to a period of time after an illness or accident 

  which could have caused death.

  "After heart surgery, some patients say they're living on borrowed time."

look the picture of health

  To look the picture of health means to look completely or extremely healthy.

  "Nice to see you again Mr. Brown.  I must say you look the picture of health!"

meet your maker

  This expression is used to say (often humorously) that someone has died.

  Poor old Mr. Potter has gone to meet his maker.

on the mend

  Someone who is on the mend is getting better after an illness.

  My grandmother has not been very well this last while but she's on the mend now.

new lease of life

  A person who has a new lease of life has a chance to live longer or with greater

  enjoyment or satisfaction.

  "Moving closer to his children has given him a new lease of life."

go nuts

  To say that a person has gone nuts means that they have become completely 

  foolish, eccentric or mad