The causes of dizziness when the patient sits up are considered as follows: 1. Consider that it is caused by postural hypotension, the patient’s usual blood pressure may be low or there is anemia and other diseases, and the patient is prone to the above symptoms when getting up too fast or too hard. But dizziness is mostly transient and may be accompanied by blackness in front of the eyes. When a person gets up suddenly after lying down or sitting down, the blood pressure is not adjusted in time and the blood supply to the brain is not adequate, resulting in episodes of dizziness. Patients must be slow to get up, if they are fast, they may have a fall. 2. If dizziness persists when the patient sits down, pay attention to the measurement of blood pressure in the prone and standing positions. If the patient’s blood pressure is persistently low in the standing position, consider that it is caused by serious diseases such as multiple sclerosis and multiple system atrophy.