A large and long-running study has given doctors new information about two common blood pressure medicines: chlorthalidone and hydrochlorothiazide.
The study followed over 730,000 people for 17 years and was done by researchers at Columbia University.
Both of these medicines are used to lower high blood pressure and help prevent serious problems like heart attacks, strokes, and heart failure. They belong to a group of drugs called diuretics, or “water pills,” which help the body get rid of extra salt and water.
The researchers found that while both drugs work well to lower blood pressure, chlorthalidone comes with more side effects. The biggest concern is that it can cause low levels of potassium in the blood.
Potassium is a mineral that helps the heart and muscles work properly. If potassium gets too low—a condition called hypokalemia—it can lead to irregular heartbeats, confusion, kidney damage, and even type 2 diabetes.
In this study, 6.3% of people taking chlorthalidone developed low potassium, compared to only 1.9% of those taking hydrochlorothiazide. That means people on chlorthalidone were about three times more likely to have this problem.
The study also found that chlorthalidone increased the risk of other issues like electrolyte imbalances and kidney problems, even when the dose was low.
Because of these results, some doctors are now asking whether chlorthalidone should still be the first medicine offered to patients with high blood pressure. It might be better for some people to take a different drug or to be watched more closely if they’re taking chlorthalidone.
High blood pressure is a serious condition that affects millions of people around the world. If it’s not treated, it can lead to heart disease, stroke, kidney failure, or early death. That’s why it’s so important to find the safest and most effective treatment for each person.
Medicine is one part of the solution, but healthy habits are just as important. Eating a balanced diet, getting regular exercise, cutting back on alcohol, quitting smoking, and reducing stress all help keep blood pressure under control. Checking blood pressure at home can also help people stay healthy and catch any problems early.
This study, led by Dr. George Hripcsak and published in the journal JAMA Internal Medicine, reminds us that no medicine is perfect. Every treatment has benefits and risks. Doctors and patients should work together to choose the best plan for each person.
With more research, healthcare providers can keep finding better ways to treat high blood pressure—ways that are both safe and effective.
If you care about high blood pressure, please read studies about potatoes and high blood pressure, and top 10 choices for a blood pressure-friendly diet
For more information about high blood pressure, please see recent studies about impact of vitamins on high blood pressure you need to know, and the powerful link between high blood pressure and a potassium-rich diet.
Copyright © 2025 Knowridge Science Report. All rights reserved.
