Hi,
Thanks for your question.
After going through your question, there is likely possibility of syncope.
Sudden black out and fainting is a part of syncope.
There are different causes for it -
1)
Postural hypotension : fall in blood pressure on standing may cause similar symptoms.
It may be due to medicine for blood pressure or due to autonomic neuropathy.
2)
Cardiac arrhythmia : Abnormal electrical activity of heart. It may be due to heart disease electrolyte abnormalities, Degenerative changes in conduction system of heart.
3) TIA (
Transient Ischemic Attack) : Transient decreases in blood supply to brain due to occlusion in blood vessels may cause similar complaints.
4) Hypoglycemia : (
low blood sugar) this is possible in patient with diabetes on treatment.
In such cases, There may be need for -
1) Detailed clinical Examination.
2) ECG, electrophysiological study of heart, Holter's monitoring, 2DEcho of heart.
3) Blood tests :
Complete blood count, kidney and liver function tests, serum calcium, magnesium.
4) Brain imaging with angiography.
Hope this helps you, if so do vote.