Health Guide

Chlorothiazide (By mouth)

Chlorothiazide (klor-oh-THYE-a-zide)

This medicine is a diuretic that treats fluid retention and high blood pressure. A lower blood pressure can reduce the risk of stroke and heart attack.

Brand Name(s):


There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to chlorothiazide or a sulfonamide (sulfa drug), or if you are not able to urinate.

How to Use This Medicine:

Liquid, Tablet

  • Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.
  • Oral liquid: Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.
  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Some medicines and foods can affect how chlorothiazide works. Tell your doctor if you are also taking any of the following:
    • Cholesterol medicine, such as cholestyramine or colestipol
    • Insulin or an oral diabetes medicine
    • Lithium
    • NSAID pain or arthritis medicine, such as aspirin, diclofenac, ibuprofen, or naproxen
    • Steroid medicine, such as hydrocortisone, methylprednisolone, prednisolone, or prednisone
  • Alcohol, narcotic pain relievers, or sleeping pills may cause you to feel more lightheaded, dizzy, or faint when used with this medicine. Tell your doctor if you drink alcohol or use pain relievers or sleeping pills.

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding.
  • Tell your doctor if you have kidney, liver, or heart disease, diabetes, gout, lupus, high cholesterol, a mineral imbalance (such as low calcium), asthma, or allergies.
  • This medicine could lower your blood pressure too much and cause you to feel dizzy or lightheaded. Stand or sit up slowly if you are dizzy. This is more likely to happen when you begin to use the medicine or if you become dehydrated.
  • Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.
  • Do not stop using this medicine without asking your doctor, even if you feel well. This medicine will not cure your high blood pressure, but it will help keep your blood pressure in a normal range. You may have to take blood pressure medicine for the rest of your life.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Blistering, peeling, red skin rash
  • Bloody or cloudy urine, pain in the lower back, change in how much or how often you urinate
  • Dry mouth, increased thirst, confusion, nausea or vomiting, uneven heartbeat
  • Fever, chills, cough, hoarseness, sore throat, and body aches
  • Headache, lightheadedness, dizziness, or fainting
  • Muscle cramps or twitching, weakness, drowsiness
  • Severe stomach pain
  • Unusual bleeding or bruising
  • Yellow skin or eyes

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 7/4/2018
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