Brief Answer:
it depends

Detailed Answer:
Hello,

the symptoms depend on the involved organ. For example bleeding in the gastrointestinal tract may cause any (or all) of the following:
- melena (black tarry stool) particularly when the bleeding site is in the upper gastrointestinal tract
- anemia (particularly if bleeding occurred in the lower part of the gastrointestinal tract as occult bleeding)
- symptoms of significant blood loss (hypotension, sweating, fading, tachycardia, thirst, etc)
- hematochezia that is visible blood mixed with the stool.

Bleeding in the brain will cause stroke. The symptoms will depend on the extent of bleeding, the pressure the blood will exert on the brain tissue and the part of the brain that's involved ranging from coma and death to mild symptoms (like headache with barely noticeable neurologic symptoms).

Bleeding the urinary tract will cause hematuria and perhaps obstruction of the urinary tract (due to the formation of blood clots).

Since you've noticed dark stool you'd better visit your doctor for assessment as soon as possible. Ongoing bleeding from the gastrointestinal tract may become life-threatening!

I hope you find my comments helpful!
Kind Regards!

---