Hi, This is called postural or orthostatic hypotension. When a person stands after a lying position or sitting position, due to sudden change of posture, the blood accumulates in the lower part of body due to gravitation. It will result in lower blood available to upper part of body, particularly to brain. This causes symptoms of passing out. In pediatric practice, this is of not much worry and symptoms only persist for a period of few minutes. However, preventive measures should be taken, as it may cause a fall on some hard surface, particularly in staircase etc. Such patients should should bring the head downward, by bending forward, so that the level of head is down as compared to your heart. Always, make some exercises of lower part of body before standing up, so that the blood accumulated in the legs, go in circulation, giving more blood supply to brain. These episodes are frequent, more in thin children and hence to add a few ponds of weight may be beneficial in such children. Taking adequate fluids and three times healthy diet may reduce the frequency of orthostatic hypotension. In some cases, adding salt to diet may be beneficial. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Satnarain Bansal, General & Family Physician