For many people with high blood pressure, taking medicine every day is part of life. These drugs help control blood pressure and reduce the risk of heart attacks and strokes.
But new research from Columbia University suggests that one of the most common medicines, chlorthalidone, may cause more side effects than doctors once believed.
Chlorthalidone is a type of diuretic, often called a “water pill.” It helps your body get rid of extra salt and water by making you urinate more. This reduces pressure on your heart and blood vessels.
For many years, medical guidelines have recommended chlorthalidone instead of a similar drug called hydrochlorothiazide because experts thought it offered stronger protection for the heart. However, new research challenges this idea and shows that the two drugs work about the same—but chlorthalidone might come wi…
The Columbia University team studied medical records from more than 730,000 people treated for high blood pressure over a period of 17 years.
They found that both chlorthalidone and hydrochlorothiazide were equally effective at lowering blood pressure and preventing heart attacks, heart failure, and strokes. But when they looked at the side effects, they found a big difference.
People taking chlorthalidone were almost three times more likely to have low potassium levels than those taking hydrochlorothiazide. This condition is called hypokalemia. Potassium is very important for heart and muscle function.
When potassium levels drop too low, it can cause irregular heartbeats, muscle weakness, or even paralysis in severe cases. In this study, 6.3% of people taking chlorthalidone developed low potassium…
Even when patients took smaller doses of chlorthalidone, they were still more likely to develop low potassium compared to those on hydrochlorothiazide.
The researchers also found that people taking chlorthalidone were at higher risk of low sodium levels—a condition called hyponatremia. Sodium helps control the body’s fluid balance and nerve function. When sodium gets too low, it can cause confusion, headaches, or even seizures…
The study also showed a higher risk of kidney problems among patients who took chlorthalidone. While the medicine effectively lowers blood pressure, it may also strain the kidneys or upset the body’s balance of electrolytes—important minerals like sodium, potassium, and magnesium that help control many body functions.
The scientists suggested that doctors should watch their patients carefully when prescribing chlorthalidone. Regular blood tests to check for changes in electrolytes and kidney function can help catch problems early. This is especially important because symptoms such as weakness or tiredness can appear mild but still signal serious imbalances.
This isn’t the first time concerns about chlorthalidone have been raised. Other studies have also shown that it can cause more salt and mineral imbalances than hydrochlorothiazide. Still, many doctors prefer chlorthalidone because of its strong track record for controlling blood pressure and reducing heart disease risk.
The researchers, led by Dr. George Hripcsak, published their findings in *JAMA Internal Medicine*. They hope this study encourages doctors to weigh the pros and cons of each medication carefully. If both drugs protect against heart disease equally well, then the one with fewer side effects—hydrochlorothiazide—might be the safer choice for many patients.
For people currently taking chlorthalidone, this doesn’t mean they should stop suddenly. Instead, it’s important to talk to a doctor before making any changes. In some cases, chlorthalidone may still be the right choice, but monitoring for side effects is key.
This research is another reminder of how important personalized medicine is. Each person reacts to medications differently, and the best treatment depends on individual health conditions and risks. For those managing high blood pressure, having the right medicine can protect not only their heart but also their overall well-being.
If you care about blood pressure, please read studies that new research challenges conventional blood pressure guidelines and scientists make a big breakthrough in high blood pressure treatment.
For more about blood pressure, please read studies that widely used blood pressure drug may increase eye disease risk and common blood pressure drugs linked to cognitive decline.
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