My gf is losing blood from somewhere and the doctors can't find out where.?

Blood loss?: Blood loss can be genital (uterine/vaginal), urinary (kidneys/bladder, gastrointestinal (somewhere in the gut), "internal": into the abdomen, behind the abdomen (retroperitoneal), into the chest (thoracic, mediastinal), an extremity. Can also be premature breakdown of cells (hemolysis) due to lots of causes; marrow problems-not making blood cells. Keep looking- cause may be a challenge to find.