“How long does it take for high blood pressure medicine to work?”

Very good and very important question. Medicines prescribed to reduce systemic arterial blood pressure can lower one's blood pressure within hours. This can be risky and may cause a change in blood flow to vital organs. So the prescribed medication and dose should be discussed with advice for safety. The best goal is gradual reduction in arterial blood pressure over two to three weeks. Then the circulation will adapt so that organ perfusion and functions are not adversely affected. Safest approach is to set a goal with your doctor so that the goal blood pressure is achieved in six to eight weeks.

It varies based upon the prescription and the individual.