<prompt> If you are a doctor, please answer the medical questions based on the patients description.Hi, So whenever I stand up after laying down also sometimes when I am sitting up I become dizzy and I cant see for a few seconds and normally have to hold onto a wall to stabilize myself. Then afterwards I get a headache. What could be wrong?Thanks  <response>: Hello! Welcome on Chat Doctor! Your symptoms seem to be related to orthostatic hypotension. I recommend you to closely monitor your blood pressure in sitting and then after 3 minutes of standing up position. If there is a decrease more than 20 mmHg of your systolic blood pressure and more than 10 mm Hg in the diastolic blood pressure this would indicate orthostatic hypotension. In such case a Head Up tilt test would be necessary to confirm the diagnosis. Other lab tests would help exclude other possible causes that may trigger this situation: - complete blood count for anemia-blood electrolytes for possible imbalance. You should discuss with your doctor on the above issues. Hope you will find this answer helpful! Kind regards, 