Hi, Your blood pressure may be lowering to critical levels either due to medication, dehydration, hypoglycemia, or a combination of all those factors. You may also be suffering from blockages in your carotid arteries or elsewhere reducing blood flow to the brain itself. You should see a doctor for these symptoms as soon as possible otherwise, you could hurt yourself by passing out while trying to go downstairs, driving a vehicle, or doing something else that can cause damage to yourself or others. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Dariush Saghafi, Neurologist