I'm on a blood pressure drug. My pharmacy ran out of the dose I needed and substituted a 2x size, with instructions to cut the pill in half. I ended up forget

I'm on a blood pressure drug. My pharmacy ran out of the dose I needed and substituted a 2x size, with instructions to cut the pill in half. I ended up forgetting about the substitution and took the 2x dose daily for a couple of months. Didn't find out until I went to renew the prescription and was told I was trying to refill it too early. Suddenly the recent dizzy spells I had were easily explained.