Blood oxygen levels under 90 percent are considered low and warrant immediate medical attention, according to the Mayo Clinic. A dangerous blood oxygen level, also called hypoxemia, occurs when a lower-than-average level of oxygen is circulating from the blood to the cells and tissues of the body. Normal blood oxygen levels are within the 95 to 100 percent range.
According to WebMD, symptoms of low blood oxygen levels include shortness of breath, fast heart rates, sweating, wheezing, mental confusion, coughing and changes in the color of the skin that can range from cherry red to blue. When these symptoms are experienced by any individual, WebMD recommends calling 911 emergency services immediately.
Causes of low blood oxygen levels include anemia; pneumonia; ARDs, or acute respiratory distress syndrome; COPD, or chronic obstructive pulmonary disease; pulmonary edemas; sleep apnea and congenital heart disease. Other causes of hypoxemia include interstitial lung disease, high altitudes, blocked airways and anesthetics or narcotic medications, according to the Mayo Clinic.
WebMD also lists severe asthma attacks as potentially life-threatening causes of hypoxemia. During these occurrences, the airways narrow, making it harder to get air into the lungs. Many individuals instinctively cough, which uses more oxygen and can exacerbate the problem. Therefore, individuals with asthma must always have their rescue inhalers on hand and adhere strictly to their medically supervised asthma treatment plan.