Mohammed Allan, 31, "declared in front of his doctors that if there is not any solution to his case within 24 hours he will ask for all treatment to stop and will stop drinking water," the Palestinian Prisoners Club said in a statement.
Allan, held by Israel without charge since November, went on hunger strike in protest on June 18, taking only water. He fell into a coma last Thursday night.
The prisoners club said that after regaining consciousness Allan "has agreed after detailed explanations about his condition situation to take some supplements for 24 hours while he waits for a resolution to his case".
Lawyer Jamil al-Khatib told AFP after visiting his client in hospital that Allan appeared determined to go all the way, although there was still hope the judiciary would find a solution.
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Israel's High Court will on Wednesday continue hearing a petition by Allan's lawyers calling for his release on medical grounds.
The justice ministry released a statement ahead of Monday's hearing that included an offer to free Allan, a lawyer from the northern West Bank town of Einabus, "if he agrees to go abroad for a period of four years".
His legal team immediately dismissed the proposal.