Hello! Thank you for asking on HCM! I read your question and would explain that your systolic blood pressure is below the normal limits. This means that you have low blood pressure, which is the cause of your symptomatology (dizziness and lightheadedness). It may be related to lisinopril intake. But other causes (dehydration, chronic anemia, metabolic disorders) should be excluded first. I recommend consulting with your attending physician for a careful physical examination, a resting ECG and some blood lab tests: - complete blood count ( for chronic anemia) - thyroid hormone levels - cortisol plasma levels - fasting glucose - blood electrolytes - kidney and liver function tests, etc. An ambulatory 24-48 hours ECG monitoring and a cardiac ultrasound would be necessary to examine better your cardiac function and exclude possible cardiac related causes. A head up tilt tests is needed to rule in/out possible orthostatic hypotension. Do you feel difficulty breathing or heart palpitations? Meanwhile you should carefuly monitor your blood pressure in sitting and standing up position. If all the above tests result normal, I would recommend reducing the dose of lisinopril or switch into a beta-blocker therapy, to help maintain a normal heart rhythm and blood pressure and avoid tachycardia. Hope to have been helpful! Best wishes, Dr. Iliri