Hypotension is rarely a disease in itself. It is either a symptom of some other disease, malfunction or impairment, or it is a side-effect of various types of medication.

Medications that most commonly cause hypotension are drugs that affect heart rate, such as calcium channel blockers and beta blockers. Taken for regulating high blood pressure, they can slow the number of times the heart contracts per minute. Calcium channel blockers reduce the blood pressure by dilating the arteries, while beta blockers prevent the effects of hormones such as epinephrine and norepinephrine, thereby decreasing blood pressure. The level of hypotension caused in these events depends on the dosage of medicine and the state of health of the heart and other related organs. Medications like ACE inhibitors, used to reduce the activity of the ACE enzyme, can trigger the production of chemicals that constrict blood vessels, causing hypotension.

Diuretics that increase the level of fluid excretion can decrease the level of water in the blood, decreasing its volume. This can cause the brain to receive inadequate blood, resulting in hypotension. Medications for erectile dysfunction, such as Viagra, and antidepressants can also cause hypotension.

Low blood pressure can also occur as a side-effect of chemicals, toxins or other substances in certain medications, so they should not be taken unless prescribed by a doctor.