Hi should i worry if for the past couple of days my stool has been half brown half very dark brown very similar to black ?

Perhaps: Without more information I would say Yes be worried. If you are concerned enough to write in I would go to a doctor and get a Fecal occult blood test done. This will see if the color is due to blood in the stool. Foods like dark vegetables can change the stool color. Certain meds can cause GI bleeding. See a doctor.

I don't think you: need to worry, but I would continue to watch it. Very likely the dark brown digested products of something you ate or took (especially iron) were processed and collected up against your usual color stool. I predict in another day or two it will normalize. The most worrisome thing is if the black stool represents old blood is present. If it persists, see Doc; consider stool test for blood.