The blood oxygen level is the amount of oxygen circulating in the blood. A healthy blood oxygen level varies between 75 and 100 millimeters of mercury (mm Hg) . The most common way to measure blood oxygen level is with a pulse oximeter, which measures the percentage of oxygen in the blood. A healthy oxygen saturation level ranges between 95% and 100% . For most people, a normal pulse oximeter reading for oxygen saturation level is between 95% and 100% . However, people with certain conditions, such as COPD, may need to maintain their blood oxygen at a different level, so it is important to speak with a doctor to determine the ideal or realistic level for you. If oxygen levels are below 88%, that is a cause for concern, and you should seek medical attention immediately. Symptoms of low blood oxygen levels include shortness of breath, chest pain, coughing or wheezing, confusion, headache, rapid heartbeat, and a blue discoloration of your nail beds, skin, and mucus membranes.