Symptoms of dementia before death in the late stage can be manifested as abnormal mental state, impaired consciousness, abnormal vital signs and so on. If patients have the above symptoms, they should go to regular hospitals to exclude other causes of disease and follow the doctor’s instructions for standardized treatment to avoid delaying their condition. 1. Abnormal mental state: patients are easy to be emotionally unstable in the late stage, and some of them may have indifferent expression and be silent, while others may be agitated and irritable. 2. Impaired consciousness: the patient’s impaired consciousness will gradually aggravate, and there is no sense of independent feeding and independent defecation. 3. Abnormal vital signs: patients may have irregular respiratory rhythms, slow heart rate, drop in blood pressure, and may die at any time.