Dark stools

Recently I've had very dark, almost black stools accompanied by nausea.  Any idea what could be causing this?

[MARY ANN]

it could be many digestive complications go to a gasto /digestive specialest asap you could be bleeding from some where in your systm . black stool is normaly an indication of bleeding .do not put off going to a hospital or doctor now. best of luck.

[Wilson]

Dark stools are often associated with bleeding in the upper GI tract, which would make sense with your nausea. Blood in the stool is brighter red when it's from lower in the tract, as it's more fresh. Your dark stools might just be a reflection of your diet, or could be an ulcer - who knows? But you definitely need to see a GI specialist soon if your symptoms persist.
Best wishes.

[Dr. Erik]

I agree with both Mary Ann and Wilson. Do not delay in seeing a gastroenterologist.

[buschy]

Does eating a lot of spinach cause dark stools...I have had for a day and a half these half dark and half normal stools.  I only noticed this after having ate a big plate of spinach on Saturday.  

Any comments??