Q.

It is a 9 letter word- 123456789,
If u lose it you will die,
If you have 234, you can 1234,
56 is one type of disease,
89 indicates exact location & time,
2 & 7 are same letter, 3 & 8 are same letter, 5 & 9 are same letter.
Guess the word???

A.

Heartbeat

Thanks to Pradip Desai for answer