You should not use chlorthalidone if you are unable to urinate, or if you are allergic to sulfa drugs.
Before taking this medicine
You should not use chlorthalidone if you are allergic to it, or if:
you are unable to urinate; or
you are allergic to sulfa drugs.
Tell your doctor if you have ever had:
kidney disease;
heart failure;
gout;
high cholesterol or triglycerides;
diabetes; or
if you are on a low-salt diet.
Tell your doctor if you are pregnant or plan to become pregnant. Taking chlorthalidone during pregnancy may cause side effects in the newborn baby, such as jaundice (yellowing of the skin or eyes), bruising or bleeding, low blood sugar, or an electrolyte imbalance.
Do not start or stop taking chlorthalidone during pregnancy without your doctor's advice. Although chlorthalidone may cause side effects in a newborn, having high blood pressure during pregnancy can cause complications such as diabetes or eclampsia (dangerously high blood pressure that can lead to medical problems in both mother and baby). The benefit of treating hypertension may outweigh any risks to the baby.
You should not breastfeed while using chlorthalidone.
How should I take chlorthalidone?
Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.
Call your doctor if you are sick with vomiting or diarrhea, or if you are sweating more than usual. You can easily become dehydrated while taking chlorthalidone. This can lead to very low blood pressure, a serious electrolyte imbalance, or kidney failure.
Your blood pressure will need to be checked often. Your blood and urine may both be tested if you have been vomiting or are dehydrated.
 chlorthalidone can affect the results of certain medical tests. Tell any doctor who treats you that you are using chlorthalidone.
If you need surgery, tell your surgeon you currently use this medicine.
If you have high blood pressure, keep using this medicine even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medicine for the rest of your life.
Store this medicine at room temperature away from moisture, heat, and light. Keep the bottle tightly closed when not in use.
What happens if I miss a dose?
Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include nausea, weakness, dizziness, drowsiness, extreme thirst, muscle pain, or rapid heartbeats.
