Though the pulse oximeter actually measures the saturation of oxygen in your blood, the results are often used as an estimate of blood oxygen levels. Normal pulse oximeter readings range from 95 to 100 percent, under most circumstances.Values under 90 percent are considered low.1  Causes.ypoxemia, or low blood oxygen, describes a lower than normal level of oxygen in your blood. In order to function properly, your body needs a certain level of oxygen circulating in the blood to cells and tissues.