Feeling tired after getting 8 hours of sleep can be due to several reasons including sleep inertia, poor sleep quality, sleep disorders, stress and anxiety, lifestyle factors, or an individual need for more than 8 hours of sleep. Sleep inertia is a normal groggy feeling after waking up that can last from 15 minutes to two hours. Poor sleep quality, meaning not enough deep or REM sleep, can leave you feeling unrefreshed. Sleep disorders like sleep apnea can interrupt your sleep cycles, preventing restorative rest. Stress, anxiety, and an inconsistent sleep schedule also interfere with feeling rested. Additionally, genetic and individual differences mean some people simply need more than 8 hours of sleep to feel fully rested. Lifestyle factors such as diet, hydration, exercise, and environment also play a role. If the fatigue is persistent, it might be beneficial to evaluate these factors or consult a healthcare professional for sleep disorders or other underlying conditions.