Low pressure and oxygen in your blood
Low blood pressure, or hypotension, is when your blood pressure is lower than normal. The opposite is high blood pressure or hypertension.
Your blood pressure naturally changes throughout the day. Your body constantly adjusts and balances your blood pressure. This helps to make sure every part of your body — including the brain, heart, and lungs — is getting plenty of blood and oxygen.
Low blood pressure can be normal. It may not cause any symptoms or be a cause for concern.
Blood pressure may even change with your body position. For example, if you stand up suddenly, it may drop for an instant. Your blood pressure also lowers when you’re resting or asleep.
Some health conditions can cause low blood pressure. This can lead to too little blood and oxygen to some parts of your body. Treating the condition helps to raise blood pressure.
What causes hypotension?
Everyone’s blood pressure drops at one time or another. And, it often doesn’t cause any noticeable symptoms. Certain conditions can cause prolonged periods of hypotension that can become dangerous if left untreated. These conditions include:
pregnancy, due to an increase in demand for blood from both mother and the growing fetus
large amounts of blood loss through injury
impaired circulation caused by heart attacks or faulty heart valves
weakness and a state of shock that sometimes accompanies dehydration
anaphylactic shock, a severe form of allergic reaction
infections of the bloodstream
endocrine disorders such as diabetes, adrenal insufficiency, and thyroid disease
Medications might also cause blood pressure to drop. Beta-blockers and nitroglycerin, used to treat heart disease, are common culprits. Diuretics, tricyclic antidepressants, and erectile dysfunction drugs can also cause hypotension.
Some people have low blood pressure for unknown reasons. This form of hypotension, called chronic asymptomatic hypotension, isn’t usually harmful.