These four groups are further categorized based on whether a protein, called Rhesus (Rh) factor, is present on the surface of red blood cells. Each of the four main groups can be either Rh-positive (+ ...

The blood bank that serves Humboldt and Del Norte counties is in urgent need of O positive blood, with a holiday slowdown in donations. It’s the most common blood type. Kate Witthaus ...

It's a bit simplistic, but you can think of the Rh factor as a protein that is either present (positive) or absent (negative) on red blood cells. Exact percentages vary with race, but most people ...