Your doctor may do blood tests to check your electrolyte levels when you start taking chlorthalidone and while you are taking it. Electrolytes are minerals in the blood. They help control important functions in the body.

Changes in electrolyte levels are common with chlorthalidone. It is an expected effect of the medicine. Chlorthalidone can cause low levels of the following electrolytes:

  • Potassium
  • Sodium
  • Magnesium
  • Chloride

Chlorthalidone can also cause an increase in calcium in the blood.

Small changes in electrolyte levels are okay, but big changes can be dangerous. Because of this, your doctor may do blood work to make sure your electrolyte levels are in a safe range.