Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
a light-headed feeling, like you might pass out;
low sodium--headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
low potassium--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling;
low magnesium--dizziness, irregular heartbeats, feeling jittery, muscle cramps, muscle spasms, cough or choking feeling; or
kidney problems--little or no urination, swelling in your feet or ankles, feeling tired or short of breath.
Common side effects may include:
low blood pressure (feeling light-headed);
kidney problems;
dizziness; or
an electrolyte imbalance (such as low levels of potassium, sodium, or magnesium in your blood).
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Chlorthalidone side effects (more detail)
