Chlorthalidone is a trusted medicine that has been used by doctors to treat high blood pressure for over 50 years.

Many people wonder about their chances of experiencing side effects when they take a medicine. Even with a well-used medicine like chlorthalidone, it’s not possible to predict your exact chances of developing a side effect.

However, some studies of chlorthalidone did measure how frequently side effects occurred. We know side effects can be scary, which is why we’ll use one of these studies to help explain a little more about them. The more you know, the better you can prepare yourself, and those side effects might not seem so scary after all.

The study we’ll talk about today used a large group of people, all over the age of 60, both male and female, and of various races and ethnicities. Most importantly, all the participants in this study had high blood pressure.  Scientists divided these people into two groups: one group started blood pressure treatment with chlorthalidone, and one group with a sugar pill, called a placebo. The people did not know which group they were assigned to, so they did not know if they were really taking chlorthalidone or the placebo. Scientists then tracked which symptoms patients in each group reported as the most bothersome.

Remember that everyone in this study had high blood pressure. Many of the symptoms participants reported occur with high blood pressure alone, so if you have high blood pressure, you may experience these symptoms with or without your medicine. This study showed that chest pain or heaviness, and unusual joint pain occurred in 6 more people in the chlorthalidone group than in the placebo group. On average, 26 people out of 100 taking placebo said they experienced chest pain or joint pain, while 32 people out of 100 on chlorthalidone said they experienced chest pain or joint pain. That’s a difference of 6 people out of 100.

Faintness or lightheadedness upon standing, cold or numb hands, ankle swelling, falling, changes in bowel habits, and waking up in the night to urinate occurred in 3 more people out of 100 in the chlorthalidone group, compared to the placebo group. On average, 12 out of 100 people taking the placebo said they felt lightheaded, had cold or numb hands, ankle swelling, falling, changes in bowel habits, or frequent urination. A total of 15 out of 100 people taking chlorthalidone said they felt one of these symptoms. That’s a difference of 3 out of 100 people.

Loss of consciousness, slow heartbeat, excessive thirst, male sexual dysfunction, and skin rashes, all occurred in just 1 more person out of 100 in the chlorthalidone group, compared to the placebo group. On average, 5 out of 100 people taking the placebo said that they experienced fainting, slow heartbeat, male sexual dysfunction, excessive thirst, or skin rashes. A total of 6 out of 100 people taking chlorthalidone said they experienced one of these symptoms. That’s just one more person out of 100.

Although no one can know their exact risk of side effects, this study shows us that side effects from chlorthalidone are actually pretty uncommon. Some of these side effects may also fade over time. If you experience a side effect from chlorthalidone, talk to your doctor about your options.

Remember, although chlorthalidone may slightly raise your risk of developing these symptoms, it also lowers your blood pressure and works to keep you healthy.

Even common side effects are not so common!