Hi Dee,
Hypotension or low blood pressure is usually when blood pressure drops to 90/60 or below. However, individuals with previous heart issues may show symptoms of low blood pressure at 100/60. The most common symptoms for low blood pressure are lightheadedness and fatigue. It's very possible that your dizzy/sleepiness is related to your low blood pressure. I recommend you speak with your MD regarding your symptoms and blood pressure reading to determine if there is reason for concern.
All the best,
Lisa Nelson, RD, LN
The Heart of Health ezine