Causes of low blood pressure

An ideal blood pressure is usually lower than 120/80 mm Hg.

The first (upper) number is the pressure in the arteries when the heart beats (Systolic pressure).

The second (bottom) number is the pressure in the arteries when the heart rests between beats (Diastolic pressure).

Blood pressure is usually lowest at night and rises sharply on waking.

Blood pressure varies throughout the day depending on body position, breathing, food and drink, medications, physical condition, stress and time of day.

Certain health conditions and use of medications may also cause low blood pressure.

These include water pills (diuretics), drugs for erectile dysfunction, and certain types of antidepressants.

Pregnancy, hormone-related diseases, dehydration, blood loss, lack of nutrients in the diet, heart and heart valve conditions, severe allergic reaction (anaphylaxis) or severe infection (septicemia) may also cause low blood pressure.