As a respiratory expert, I can tell you that it's normal for oxygen levels in the blood to be slightly lower during sleep due to a mild decrease in the level of breathing. This is a natural part of the body's rest cycle. Additionally, some of the tiny air sacs in the lungs, known as alveoli, may not be as active during sleep, which can also contribute to a slight drop in oxygen levels. However, if your oxygen saturation when you're awake is above approximately 94 percent while breathing room air, it's generally not expected to fall below 88 percent during sleep. An oxygen saturation level of 88 percent is considered the lower limit of what's deemed safe for most healthy adults. It's important to note that individual health conditions, altitude, and other factors can influence these numbers. If there are concerns about oxygen levels during sleep, it's best to consult with a healthcare professional for a personalized assessment. read more >>

Everyone's oxygen levels in the blood are lower during sleep, due to a mildly reduced level of breathing. Also, some alveoli drop out of use during sleep. If your waking oxygen saturation is greater than about 94 percent on room air, it is unlikely that your saturation during sleep will fall below 88 percent.read more >>