What can use for low blood pressure. my mother suffer of high blood pressure, but sometimes it falls very low

Her : Her doctor needs to be advised. Depending on the extent of hypotension, her doctor may need to adjust her medications.

Unless : Unless she is monitoring the question i would have is how do you know she is low. If she gets lightheaded with standing, i would inform her doctor. Some medications are more likely to cause drop in pressure with standing. If there is a question of her pressure throughout the day and night, some practices will have access to a home monitor that mom would wear over 24 hours, measuring and recording the blood pressure. This is called ambulatory blood pressure monitoring. Talk to the doc. A change in meds may be needed.