Hypotension is the medical term for low blood pressure. Optimal blood pressure is less than 120/80 (systolic pressure is 120 AND diastolic pressure is less than 80). Within certain limits, the lower your blood pressure reading is, the better. There is no specific number at which day-to-day blood pressure is considered too low as long as you are not experiencing symptoms of low blood pressure such as dizziness, fatigue and nausea. If you are experiencing these symptoms, you should contact your doctor to determine the cause.