Doctors at Memorial Hermann Texas Medical Center Hospital determined the congresswoman was healthy enough to move to nearby TIRR Memorial Hermann, where she will continue her rehabilitation work.
An ambulance transported her a short way to TIRR, which stands for The Institute for Research and Rehabilitation. Helicopters buzzed overhead and there was a heavy police presence. Video from a news helicopter showed a gurney wheeled into the building.
Giffords had been in intensive care since her arrival Friday from Tucson, Ariz.
Last week doctors placed a tube in her head to drain excess cerebrospinal fluid. Her move out of ICU suggests that tube might have been removed, which would be another good sign in her recovery. A backup of the fluid can cause pressure and swelling within the brain.
Giffords was shot in the head Jan. 8 in a rampage that killed six people and injured her and 12 others. The three-term Democratic congresswoman was hit in the forehead while meeting with constituents outside a Tucson supermarket.
The alleged assassination attempt cast a somber mood over President Barack Obama's State of the Union speech on Tuesday night, where many lawmakers in both parties wore black-and-white lapel ribbons to signify the deaths and the hopes of the survivors. Giffords' husband, astronaut Mark Kelly, watched the speech from her bedside in Texas, as he held her hand.
The 22-year-old suspect in the shootings, Jared Loughner, pleaded not guilty Monday to federal charges of trying to assassinate the congresswoman and two of her aides. He also faces federal murder charges in the deaths of a federal judge and a Giffords aide, and more charges were expected.