The most common side effect is low blood pressure caused by the loss of too much fluid. This is more common in people over the age of 65, and in people taking other medications that can lower blood pressure. An early sign of becoming fluid depleted is becoming dizzy or lightheaded when standing up. Always get up slowly, especially at night or first thing in the morning. If you do feel dizzy, lay back down and call your provider.
Diuretics can also cause changes in blood minerals or electrolytes.
You will be asked to have periodic blood tests to check these. Trying to eat foods high in potassium is sometimes helpful. Ask your provider or dietitian if you should do this. If you are trying to cut down on salt, use of a salt substitute may be helpful as well as adding potassium to your diet. If you are diabetic, the diuretic may increase your blood sugar.