A blood oxygen level measures the amount of oxygen circulating in your blood. A normal blood oxygen level is usually between 95% and 100% . However, some people with chronic lung disease or sleep apnea can have normal levels around 90% . An ideal oxygen level is between 96% and 99% . If your blood oxygen level falls below 88%, it 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. It is important to note that pulse oximeters are not always accurate, and your actual blood saturation level may be 2% to 4% higher or lower than what the oximeter reads. If you have any questions about your blood oxygen level, be sure to ask your healthcare provider.