Sitting up dizziness may be caused by postural hypotension, hypoglycemia, vestibular dysfunction and other reasons. 1. Postural hypotension: when you suddenly change from sitting to standing, the blood will pool in the abdominal cavity and the venous system of the lower limbs due to the effect of gravity, resulting in insufficient return blood flow to the heart, which may lead to dizziness, darkness, etc. Low blood glucose: when you have low blood glucose due to insufficient dietary intake, you may feel dizzy when you suddenly change from sitting to standing. 2. Hypoglycemia: Hypoglycemia caused by insufficient dietary intake may lead to dizziness, palpitation, cold sweat and other symptoms after suddenly changing from sitting to standing position. 3. Vestibular dysfunction: including positional vertigo, Meniere’s disease, etc. The sudden change of head position from sitting to standing will cause abnormal reaction of the vestibular function, resulting in dizziness due to a sense of rotation of the surrounding environment. If you experience dizziness after sitting up or standing up repeatedly, it is recommended that you go to the hospital in time to have the cause clarified under the doctor’s diagnosis and actively deal with it.