Subsequent studies have been mixed. A 2014 observational study of more than a million patients argued that the J-curve does not exist, but a 2018 randomized clinical trial of more than 30,000 patient suggests that it does. Over all, there is little evidence to support lowering systolic or diastolic blood pressure below the levels of current guidelines.

Doctors do agree, however, that symptoms are an unequivocal sign of excessively low blood pressure.

Lightheadedness, particularly lightheadedness that occurs upon standing, is the cardinal symptom of low blood pressure. At its extreme, lightheadedness may result in fainting. Fainting may be a sign that blood pressure is dangerously low and requires prompt medical attention. Other possible symptoms of low blood pressure include nausea, fatigue and blurry vision.

Symptoms of low blood pressure can sometimes be a result of too much blood pressure medication or too many blood pressure drugs. If you have symptoms, your doctor may decrease your dose, discontinue one of your medications, or switch to a different medication. Your doctor can also evaluate whether you have heart problems or other conditions that may be making your blood pressure low.

Because many questions remain unanswered about optimal blood pressure management, and because the consequences of excessively low blood pressure can be serious, it is essential to stay within guideline recommendations. Doing so is the best health advice for the 75 million people — or roughly one in three adults in the United States — who have high blood pressure.

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