Chlorthalidone is a medication that doctors have long prescribed to help manage high blood pressure. But now, new research from Columbia University is raising important questions about its safety.
According to this large study, while chlorthalidone works well to prevent heart problems, it may come with some unwanted side effects that patients and doctors should be aware of.
High blood pressure, or hypertension, happens when the force of blood against the walls of your arteries is too strong—like cars speeding too fast on a highway. Over time, this can damage your heart, brain, kidneys, and other organs.
That’s why it’s important to keep blood pressure within a healthy range. Doctors often use medications, along with lifestyle changes, to help patients control it.
One of the commonly used medicines for this is chlorthalidone, a type of water pill (or diuretic) that helps the body get rid of extra salt and water. This lowers the amount of fluid in the blood vessels, which helps reduce blood pressure.
The Columbia University researchers looked at the medical records of over 730,000 people who were treated for high blood pressure over 17 years. They compared chlorthalidone to another similar drug called hydrochlorothiazide. Both drugs were effective in lowering blood pressure and preventing serious problems like heart attacks and strokes.
However, there was a significant difference in side effects. People taking chlorthalidone were three times more likely to develop hypokalemia—a condition where potassium levels in the blood drop too low.
Potassium is a mineral that your body needs to keep your heart, muscles, and nerves working properly. If levels get too low, it can lead to fatigue, muscle weakness, irregular heartbeats, or even more serious heart problems.
The numbers were clear:
- 6.3% of people on chlorthalidone developed hypokalemia
- Only 1.9% of people on hydrochlorothiazide had this issue
And that’s not all. Chlorthalidone users were also more likely to experience electrolyte imbalances and kidney problems, which can be dangerous if left untreated.
This doesn’t mean that chlorthalidone is unsafe for everyone. Many people take it without any problems. But the findings do suggest that patients on this medication should be monitored more closely. Regular blood tests to check potassium and kidney function can catch any issues early.
If you’re taking chlorthalidone and feel unusually tired, weak, or notice muscle cramps, it’s a good idea to talk to your doctor. Don’t stop taking the medication without medical advice—your doctor can help you decide whether it’s still the best option or if another treatment might be safer for you.
Doctors often choose chlorthalidone because it lasts longer in the body and may offer better blood pressure control than other drugs. But based on these new findings, some may reconsider and explore other options.
While medications can help, healthy habits are just as important. Eating a diet rich in fruits, vegetables, and low in salt can support good blood pressure. Exercise, quitting smoking, limiting alcohol, and managing stress—through yoga, meditation, or simply taking a walk—are also effective ways to keep your blood pressure in check.
Researchers will continue studying chlorthalidone and other blood pressure drugs to learn more about their long-term effects. This study is an important reminder that while medications can be powerful tools, they aren’t perfect. Careful monitoring and open conversations between patients and doctors are essential to make sure the treatment is both safe and effective.
If you’re taking any blood pressure medication, it’s always wise to ask your doctor about side effects, schedule regular check-ups, and stay informed—your heart and kidneys will thank you.
If you care about kidney health, please read studies about pesticide linked to chronic kidney disease, and this drug may prevent kidney failure in people with diabetes.
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