People with sleep apnea are particularly prone to waking and continuing to feel unrefreshed after they have slept for a considerable amount of time. In typical sleep, people feel refreshed and alert after sleep and ready to begin the new day. However, when people suffer from sleep apnea, even a full night's rest is not likely to leave them feeling good and ready to get out of bed. People who feel unrefreshed after they wake up are also likely to have difficulty concentrating on individual topics, and they are more prone to having difficulty remembering current or past events. Personality changes may also occur.

Sleep apnea is one of many sleep orders that is associated with heart failure and prone to being affected by blood oxygen levels. People with sleep apnea may also experience unusual weight gain due to the body's increased difficulty regulating weight due to a lack of consistent sleep. Lowered blood oxygen levels are common in people with sleep apnea, as is loud snoring and inflamed or enlarged tonsils. Other areas of the body such as the nasal and respiratory systems may also become swollen due to apnea; a large tongue is not uncommon and is often one of the signs that first drives people to seek the input of physicians and other health professionals.

There are a number of additional risk factors that may occur if sleep apnea is left untreated; some of these risk factors may appear as signs or symptoms of sleep apnea and may serve as a protective factor by alerting people of the need to seek medical attention. Narcolepsy, or the tendency to fall asleep at any time during the day, also becomes more common with sleep apnea, as does hypersomnia, or excessive sleepiness, and morning headaches. People wondering if they are afflicted with sleep apnea may also wish to check if they have a deviated septum, as this may increase the risks of complications, as may a soft palate or any obstructions within the upper airway.

Additional symptoms of sleep apnea include headaches. In fact, close to half of all people afflicted with sleep apnea are likely to report experiencing occasional to frequent headaches. Having headaches by itself does not make a person more likely to have sleep apnea, but experiencing frequent morning or night headaches may be a sign that closer medical attention is warranted. Similarly, experiencing heartburn or a bitter taste in the mouth during the evening hours is also likely to be due to sleep apnea, as is swelling of the legs overnight.