Hydrochlorothiazide is a diuretic, which is commonly referred to as a "water pill." It works by increasing the amount of salt and water that the kidneys remove from the blood. This extra salt and water is passed out through the urine. By increasing the amount of water removed from the blood, hydrochlorothiazide causes a decrease in blood volume. Because of this effect, the drug can lower blood pressure and help with water retention.
A blood pressure reading consists of two numbers -- for example: 120/80. The top number is known as the systolic blood pressure, and the bottom number is the diastolic blood pressure. During clinical studies in people taking hydrochlorothiazide, both systolic and diastolic blood pressure decreased significantly.
By lowering blood pressure, the medication can decrease the risk of developing health problems, such as a heart attack or stroke, that can occur as a result of long-term high blood pressure (see Effects of High Blood Pressure).
Some general considerations for when and how to take hydrochlorothiazide include:
- The medication comes in tablet and capsule form. It is usually taken by mouth once a day, although it may be taken several times a day.
- You can take it with or without food.
- If necessary, hydrochlorothiazide tablets (but not capsules) may be split in half.
- It should be taken at the same time each day to maintain an even level of medicine in your blood. However, some people do not need to take it every day, especially those who are taking it for fluid retention.
- Because hydrochlorothiazide increases urination, it is best to take it in the morning (to avoid needing to get up to use the bathroom throughout the night). If you take it multiple times per day, it is best to the take the last dose of the day before 6 PM (unless you are instructed otherwise).
- For the medication to work properly, you have to take it as prescribed; it will not work if you stop taking it.