Former US military intelligence analyst Chelsea Manning tried to commit suicide on Wednesday, two days before a court hearing on her refusal to appear before a grand jury, a support group said.
"She was taken to a hospital and is currently recovering," the Sparrow Project said on its website.
Manning "is still scheduled to appear" on Friday before a judge in Virginia, who is to consider whether punishment against her will continue, the group said.
She was ordered back to jail in May last year for refusing to testify before a grand jury targeting anti-secrecy group WikiLeaks.
Her leak years earlier of classified documents related to the wars in Iraq and Afghanistan made her a hero to anti-war and anti-secrecy activists, and her actions helped make WikiLeaks a force in the global anti-secrecy movement.
"She remains unwavering in her refusal to participate in a secret grand jury process that she sees as highly susceptible to abuse," the Sparrow Project said.
"Ms Manning has previously indicated that she will not betray her principles, even at risk of grave harm to herself."