Hi,
I can understand your concern.
I want to know
1) Your Age.
2) Any associated diabetes, blood pressure or cholesterol problem,
heart disease.
3) Current medicines if any.
4) Habits like smoking, alcohol, any
substance abuse.
Your problem may be due to-
1) Cardiac arrhythmias abnormal electrical activity of heart.
2)
Postural Hypotension (Blood pressure drop in response to standing)
3) Decreased blood supply to brain either due to heart problem or blockages in brain arteries.
4) Effect of some drugs are you taking if any.
You should
consult cardiologist.
There is need for
1) Clinical examination, assessment of hydration.
2) Check blood pressure for any postural drop.
3) Detailed neurological examination.
Depending on it there may be need of
1) ECG, Holter's monitoring, Electrophysiological study of heart, 2DEcho of heart.
2) Blood test like CBC, Kidney and liver function test, serum electrolytes.
3) Thyroid function test.
4) Brain imaging like CT or MRI of brain with
angiography.
Till that time maintain adequate hydration, avoid staying alone.
Hope I have answered your question.
If so do vote.