The club issued a statement on Wednesday, saying Ramsey had undergone bowel surgery which would require multiple follow up procedures, ruling him out for the season.
"Cody was diagnosed with ulcerative colitis, an inflammatory bowel condition, in late 2022 which required an extended stay in hospital," said Dragons general manager Ben Haran.
"Unfortunately this ultimately required significant bowel surgery. This surgery was successful, however it will require multiple follow-up procedures over the coming season.
"This means that Cody won't be available to play NRL in the 2023 season.
"Our focus will be on Cody's medical rehabilitation and wellbeing in the first phase.
"He's been in and around training with the players and coaches recently and is having a hugely positive impact on all of us at the club."
The Dragons finished 10th with 12 wins and 12 losses last season, missing out on finals after ending the season in disappointing fashion.
Ramsey's unavailability is a massive blow to Anthony Griffin's charges as the 22-year-old was expected to don the No.1 jumper this year.
"Cody is a great character who is one of the most passionate, popular and respected members of our club and will have a significant impact on the success of the team over the coming season," said Haran.
The Dragons will also be without Tariq Sims, George Burgess, Jack Gosiewski and Josh McGuire, who all left at the end of last season.
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