The medical term used to describe low oxygen level in the blood is called hypoxia, according to WebMD. It can be a serous condition because it may result in damage to major organs, such as the brain and lungs.
Hypoxia can be caused by a number of conditions, such as a blocked airway, anemia, sleep apnea, pneumonia or certain medicines that lower a person's breathing rate, according to Mayo Clinic. Anyone who experiences shortness of breath after slight exertion should visit the doctor. If individuals experience a severe shortness of breath that comes on suddenly and hampers the ability to function, it's important to get emergency medical help.