Nowadays, most blood pressure-lowering medications need to be taken only once a day. In some cases this is because the medications are naturally long-acting, and in others because they are packaged as slow-release preparations. The goal is to lower the blood pressure throughout the day and night, and when the FDA approves a new drug, it requires proof that this is achieved with the recommended dosing schedule. A medication that is recommended for dosing once a day typically starts to work about one or two hours after it's swallowed, and exerts its maximum affect at about six hours. After that the effect gradually wears off.

You should choose a time that makes it easy for you to remember to take the medications every day. Usually this means when you get up or go to bed, or at mealtimes. Most people take their medications first thing in the morning, but most once-a-day medications can also be taken at night.