Serious side effects of chlorthalidone can occur. They include:

  • low levels of sodium
  • low levels of potassium
  • gout
  • high levels of sugar and diabetes
  • allergic reactions

Low Potassium

As many as 4 in 10 people taking chlorthalidone may get low potassium. Potassium is a mineral that your body needs to work properly. It is key for the function of nerve and muscle cells. This includes the heart muscles. Low levels can cause symptoms. These include weakness, fatigue, muscle cramps, thirst, nausea, and vomiting. Very low levels can lead to confusion, seizures, and an irregular heartbeat. This can be life-threatening.

To prevent low levels, you should eat lots of potassium-rich foods. These include vegetables, fruit, salmon, and peanut butter. Your doctor may also have you take a potassium supplement pill.

Low Sodium

Low sodium levels can cause swelling in the body’s cells. This includes the brain. Early signs are headaches and nausea. If sodium gets very low, people can have seizures or blackout. This is a medical emergency.

High Sugar

Chlorthalidone may raise sugar levels in the blood.  Some people even get diabetes. Chlorthalidone is more likely to cause diabetes than some other medicines for high blood pressure.


Gout is a buildup of urate crystals in a joint. This causes joint pain and swelling. Taking chlorthalidone can increase uric acid in the blood. This can lead to gout, especially in people who have had gout before.

Allergic Reactions

Rarely, people get an allergic reaction to chlorthalidone. This is more likely for people who have asthma or other allergies.

Regular Check-ups to Prevent Serious Side Effects

If you take chlorthalidone, you will have check-ups with your doctor. Tests are done regularly. These include checks of your levels of sodium, potassium, and sugar. This helps your doctor prevent problems before they become serious.

Studies show that taking chlorthalidone helps your heart’s health. This benefit often outweighs the risk of side effects. But everyone is different. Talk to your doctor about what is best for you.