These symptoms sound like LOW blood pressure. Is he taking any medications that might cause this? In the meantime he should get up slowly from sitting or reclining position, bend over, hands on knees when light-headed. Get a BP monitor and record BP at least 4 times per day, before and after meals. See a good specialist. My hunch is that your body is either reacting to a medication you're taking, or, if your BP is always high as you measure it, you may need a special diet plus meds.