thank you for your query... from your history, it seems that his blood pressure came down a bit suddenly...this can be due to various reasons... most common is postural hypotension that is if he is suddenly standing from a position of lying down, this can happen...this is normal and doesnot require any medical treatment generally.... however i need to ask if your father is diabetic or hypertensive...or if he has had heart attacks or history of heart failure in the past...in hypertensive patients, intake of medicines may lead to fall in blood pressure whereas in diabetic patients, hypoglycemic attacks generally cause low blood presure.... also intake of less water i.e. dehydration and less intake of salt may lead to decreased blood pressure... so as you see there are many reasons... a complete history taking, clinical examination and some investigationd might fetch us the diagnosis...otherwise these are just assumptions... hope this was helpful....