Millions of people around the world take medicine every day to control high blood pressure. High blood pressure often has no clear symptoms, but over many years it can quietly damage the heart, brain, kidneys, and blood vessels.
If it is not treated, it greatly increases the chance of a heart attack, stroke, heart failure, and kidney disease. Doctors usually recommend healthy habits such as eating less salt, exercising regularly, keeping a healthy weight, avoiding smoking, limiting alcohol, and managing stress. However, many people also need medicine to keep their blood pressure at a safe level.
Two of the most common medicines used for this purpose are chlorthalidone and hydrochlorothiazide. Both belong to a group of medicines called diuretics, often known as ‘water pills.’ They help the body remove extra salt and water through urine, making it easier for the heart to pump blood and helping lower blood pressure.
For many years, both medicines have been widely prescribed, and some medical guidelines have favored chlorthalidone because earlier research suggested it might provide stronger protection against heart disease.
A large new study now suggests that the choice between these two medicines deserves another careful look. Researchers from Columbia University followed more than 730,000 people who were treated for high blood pressure over a period of 17 years. Their findings were published in JAMA Internal Medicine. The research was led by Dr. George Hripcsak.
The scientists found that both medicines lowered blood pressure and helped reduce the risk of serious problems such as heart attacks, strokes, and heart failure. However, they also discovered an important difference in safety. People taking chlorthalidone were much more likely to develop low potassium levels, a condition known as hypokalemia.
Potassium is an important mineral that helps nerves, muscles, and the heart work properly. When potassium levels become too low, people may develop tiredness, muscle weakness, dizziness, confusion, or an irregular heartbeat.
In serious cases, low potassium can increase the risk of dangerous heart rhythm problems, kidney damage, and even raise the chance of developing type 2 diabetes.
The study found that 6.3% of people taking chlorthalidone developed low potassium levels, compared with only 1.9% of people taking hydrochlorothiazide. This means patients using chlorthalidone were more than three times as likely to experience this side effect.
The researchers also found that chlorthalidone was linked to more electrolyte problems and a greater risk of kidney-related complications. Electrolytes are minerals such as potassium and sodium that help control many important body functions. When these minerals become unbalanced, health problems can quickly develop.
These findings do not mean that everyone taking chlorthalidone should stop using it. Many patients take the medicine safely and benefit from it. Instead, the results show that doctors should carefully consider each person’s health before choosing a treatment.
Some patients may need regular blood tests to check potassium and other electrolyte levels. Others, especially people who already have kidney problems or are at greater risk of low potassium, may benefit from hydrochlorothiazide instead.
The study could also influence future treatment guidelines. As new evidence becomes available, doctors can compare the benefits and risks of different medicines more carefully. Choosing the best medicine is not only about lowering blood pressure. It is also about reducing side effects and helping people stay healthy over many years.
For patients, the message is simple. Never stop taking blood pressure medicine without speaking to a healthcare professional first. If you have concerns about side effects, discuss them with your doctor, who can decide whether extra monitoring or a different medicine would be a better choice.
Together with healthy daily habits, the right treatment can greatly lower the risk of serious heart and blood vessel diseases and improve long-term health.
If you care about high blood pressure, please read studies about unhealthy habits that may increase high blood pressure risk, and drinking green tea could help lower blood pressure.
For more information about high blood pressure, please see recent studies about what to eat or to avoid for high blood pressure, and 12 foods that lower blood pressure.
Copyright © 2026 Knowridge Science Report. All rights reserved.
