Israeli Prison Services (IPS) announced in a statement that Adnan was found unresponsive in his cell in Nitzan jail in the central city of Ramle during the pre-dawn hours of Tuesday morning.
He was brought to the Shamir Medical Center outside Tel Aviv, but was declared dead at the hospital, the IPS said.
Earlier on Sunday, an Israeli court refused to release the Palestinian hunger striker despite his deteriorating health condition.
In press remarks to the Palestinian Information Center (PIC), Adnan’s wife Randa Mousa affirmed that an Israeli court rejected the appeal submitted to release her husband on bail.
The court set another session for May 10, she added.
She had warned that her husband’s health condition was very critical as a result of his prolonged hunger strike, which he started earlier this year.
Adnan was detained on February 5 and immediately went on a hunger strike in protest against his illegal detention.
He was suffering from severe health problems as a result of the strike, including frequent vomiting of blood, severe weakness, frequent loss of consciousness, difficulty in speaking, movement, sleep and concentration, and severe pain all over his body.
Over the past 20 years, Adnan had been arrested a dozen times by Israeli forces for his political and anti-occupation activities. He spent a total of eight years behind bars.
He went on hunger strike four times during his detentions, the longest of which was a 67-day period in 2012 that resulted in his release and inspired other Palestinian prisoners held under administrative detention to follow suit.
In 2015, he once again went on a hunger strike for 56 days to protest his detention. He did the same in 2018 for 58 days.
Adnan was also arrested in 2021 and was transferred to administrative detention. He went on a hunger strike for 25 days at the time.
Hundreds of inmates have been apparently incarcerated under the practice of administrative detention.
Human rights organizations say Israel violates all the rights and freedoms granted to prisoners by the Fourth Geneva Convention. They say Israel's so-called administrative detention violates their right to due process since the evidence is withheld from prisoners while they are held for lengthy periods without being charged, tried, or convicted.
Palestinian detainees have continuously resorted to open-ended hunger strikes in an attempt to express outrage at their detention.
Israeli jail authorities keep Palestinian prisoners under deplorable conditions without proper hygienic standards.
Palestinian inmates have also been subject to systematic torture, harassment, and repression.