Oximeter readings are abnormal, or low, when they are under 90 percent, states Mayo Clinic. Normal pulse oximeter readings generally range from about 95 to 100 percent. A doctor who believes the reading is inaccurate can test a blood sample taken from an artery to measure a patient's blood oxygen.
A patient who has a blood oxygen level lower than normal suffers from hypoxemia, which causes shortness of breath, notes Mayo Clinic. The condition results when the body does not has enough oxygen circulating to tissues and cells. When a pulse oximeter is clipped onto the finger, the device measures blood oxygen saturation. Doctors use the results to gauge a patient's blood oxygen level approximately.