why did i wake up nauseous

Waking up feeling nauseous can be caused by a variety of factors including low blood sugar after an extended period without eating, acid reflux or gastroesophageal reflux disease (GERD) where stomach acid flows back into the esophagus especially when lying flat, sleep disorders or poor sleep quality, anxiety or stress, pregnancy (morning sickness), dehydration, hangover from alcohol consumption, food poisoning, gastroparesis (delayed stomach emptying), sinus congestion with postnasal drip, and other digestive issues like peptic ulcers or constipation. Each of these affects the body's digestion, blood sugar levels, or nervous system in ways that can trigger nausea in the morning.