Brief Answer:
Read below.

Detailed Answer:
I read your question carefully and I understand your concern.

A transitory lowering of blood pressure can certainly cause an episode like the one you describe, actually it is the most likely cause. However the issue is what actually caused that lowering of the blood pressure. One of the most common causes to be thought of is abnormal heart rhythm. Viagra shouldn't be the cause as by that time it should have been eliminated.

One other possible cause might be inner ear disorders which are a common cause of balance issues. Usually they manifest with vertigo, a sensation of spinning movement, nausea and vomiting are common features as well.

So a check up with your primary physician is advised to look for signs present in cases of inner ear disorders like nystagmus, check heart rate possibly with an EKG and blood pressure. At times nothing may be found and if the episode remain isolated further investigations may not be needed. If the episodes repeat more in depth tests like prolonged rhythm monitoring and heart ultrasound, metabolic panel for issues like low blood sugar and MRI for brain issues may be done.

I remain at your disposal for other questions.

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Brief Answer:
Unlikely

Detailed Answer:
Wouldn't be a common manifestation in diabetes, actually it is the opposite, low blood sugar which manifests that way. It commonly happens in diabetic patients but as a side effect of treatment lowering glucose levels too much, so since you are under no such treatment it is less likely.

Let me know if I can further assist you.

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