You must find the focus and stop bleeding. In the differential diagnose we must consider acute massive or chronic occult bleeding. The reasons of chronically occult bleeding can be for example: anal fissure or hemorrhoid, GI ulcers, cancer, intestinal helminthes, urinary calculus, postmenopausal vaginal bleeding due uterine fibroids, cancer or uncontrolled hypertension; hemolysis after artificial cardiac valve etc. Diagnose must individualized.
What to do: Stop bleeding, maintain vital function (hydration, oxygenation etc.) and increase blood production (iv iron, EPO, vitamin B 12, C, folic acid). You can find further readings in this site.
A case: A 46 year old JW woman had massive dysfunctional vaginal bleeding due to myoma uteri. Operation was planned, but her hemoglobin level was 8 mg/dl. She had to wait. Her hemoglobin dropped to 5,6. She was hospitalized; was hydrated (saline, dextrose, dextran etc. ); given Oxygen, IV iron, vitamin B12, folic acid, progesterone, tranexamic acid. Vital sings maintained and discharged. Continued with oral progesterone, iron and vitamins. In spite of vaginal bleeding, her hemoglobin raised to 12,6 after three weeks; operated and discharged in three days. Four weeks after operation, her hemoglobin raised to 14 mg/dl.