Brother cut underside of foot and now 3 toes have gone black, what does this mean please?

Could be: blood in toes or poor circulation may be early gangrene i would see a doc asap

Black Toes: Gangrene? Infection? Loss of blood supply? This sounds like the internet is the last place he needs to be. He needs an examination today in person at a doctor's office.

Trapped Blood.: I have a hard time believing that cutting the underside of the foot would sever the blood supply to three toes and the injury was not bad enough to be already treated in an emergency room. More than likely, the blackness is due to trapped blood beneath the skin due to the initial trauma. No mention of pain, coldness or the original paleness of the tissue due to avascularity. 2 remove doubt C a doc