Hello and Welcome to ‘Ask A Doctor’ service.
I have reviewed your query and here is my advice.
I think you are suffering from
orthostatic hypotension.
It can be caused by different causes.
* heart problems,
heart failure,
bradycardia, heart valve problems.
*brain problems. , levy body dementia, parkinsonism, atrophy, amiloidosis
*endocrine problems like addison ,
hypoglycaemia.
*age over 65 favorites it
*medications that cure
hypertension such b blockers, ace, nitrates
* also heat or after eating or alcohol, favorites hypo tension
Try to find cause among this and make lifestyle changes.
Keep yourself hydrated and talk to your doctor about medications you are taking.
Hope I have answered your query.
Let me know if I can assist you further.