Chelsea Manning has tried to kill herself for the second time in recent months, a lawyer for the US transgender soldier said.
Manning attempted suicide last month at the military prison at Fort Leavenworth, Kansas, said Vincent Ward.
Manning also tried to take her own life in July.
Wayne Hall, an army spokesman, would not discuss the latest attempt, citing medical privacy laws.
Manning is serving a 35-year sentence.
She was arrested in 2010 as Bradley Manning and was convicted in 2013 in military court of leaking more than 700,000 secret military and US State Department documents to WikiLeaks.
Manning was an intelligence analyst in Iraq at the time.