Your doctor might prescribe oxygen if your lungs are not getting enough oxygen to your blood (a condition called hypoxemia). The air you breathe every day contains 21 percent oxygen. Prescription oxygen is close to 100 percent pure oxygen. Because of this, it is considered a drug and must be prescribed by your doctor. Oxygen is not addictive and causes no side effects when used as prescribed. Your doctor will prescribe a specific amount of oxygen that is right for you. Home oxygen can help promote your independence and make it easier and safer for you to complete daily living activities.