Up to 38 beds could be removed and two wards closed at Western Isles Hospital in Stornoway under plans announced by the islands' health board.
NHS Western Isles said it needed to improve efficiency and help secure its long-term clinical viability.
The board said demands on hospital services have changed over the past five years.
Outpatient appointments have risen while the numbers of people requiring beds overnight have fallen.
The plans will go out to public consultation before a final decision is taken by the board in September.