Anyone got any advice please re black poo (sorry!)

My husband overnight noticed he had black poo last Tuesday. This was the same every day so he insisted on being seen (they were trying to make him go through the 8am rigmarole). He was seen on Friday and it was decided to send him to hospital under the 2 week cancer policy. He’s had an endoscopy, everyone assuming it was a bleeding stomach ulcer but nothing was found, no blood there. So it was the weekend, nothing happened. Hb on the low side but no pain or aching, looks fit and well but still the dreaded black poo! Colonoscopy due today.

You can imagine the weekend we’ve both had. Anyway, doctor saw him this morning, they are discharging him this afternoon and he has to have (or give himself?) Vitamin B injections and go back in a week? So no colonoscopy.

I know Gransnet isnt a doctors but I wondered if anyone knows if that means we can breathe now and that low vitamin B really does leading to such bleeding?