Hello, black coloured stools could be due to multiple reasons. But the most common reasons are due to gastrointestinal bleed and iron tablet consumption. I Would suggest you to get a haemoglobin report done. If there is any drop in haemoglobin, I would suggest you to undergo an endoscopy to assess for any bleed inside your gastrointestinal tract
Next Steps
get a cbc done
Health Tips
check if you are on any form of iron supplements, if persistent black stools, send us a picture of the same. thank you