Under most ordinary circumstances, typical blood oxygen levels range from 95 to 100 percent according to the Mayo Clinic. Blood oxygen levels that are less than 90 percent are considered low.
Blood oxygen level refers to the amount of oxygen that is traveling through the arteries. A sample of blood from the artery typically reveals the blood oxygen levels. Another form of testing is a pulse oximeter, which is a small device that simply clips onto the end of the finger. According to the Mayo Clinic, this device ordinarily measures oxygen saturation in blood, although the pulse oximeter helps to estimate blood oxygen levels as well.