Chlorthalidone Chlorthalidone is a tablet often prescribed to treat hypertension. A diuretic, the medication lowers blood pressure by increasing urine flow. Controlling blood pressure levels can help prevent heart failure, kidney disease and damage to the blood vessels. Read more about hypertension.
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This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective or appropriate for you. This information is not individual medical advice and does not substitute for the advice of a medical provider. If you have any questions, go to your patient dashboard and request a callback for complete information about this product and your specific health needs.
Medication name




What you should know about Chlorthalidone
  • Chlorthalidone is used to treat high blood pressure (hypertension). Lowering high blood pressure helps prevent strokes, heart attacks and kidney problems.
  • The medication is also used to reduce extra salt and water in the body caused by conditions such as heart failure, liver disease and kidney disease.
  • Decreasing extra salt and water in the body helps to decrease swelling (edema) and breathing problems caused by fluid in the lungs.
  • Chlorthalidone is a "water pill" (diuretic). It increases the amount of urine you make, especially when you first start the medication. It also helps to relax the blood vessels so that blood can flow more easily.
How to take Chlorthalidone
  • Take this medication by mouth with food as directed by your medical provider, usually once daily in the morning. It is best to avoid taking this medication within 4 hours of your bedtime to avoid having to get up to urinate.
  • Consult your medical provider or pharmacist if you have questions about your dosing schedule. The dosage is based on your medical condition and response to treatment.
  • Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day. Keep taking this medication even if you feel well. Most people with high blood pressure do not feel sick.
  • If you also take certain drugs to lower your cholesterol—for example, bile acid-binding resins such as Cholestyramine or Colestipol—take this product at least 2 hours before or at least 4 hours after these medications.
  • Tell your medical provider if your condition does not improve or if it worsens—for example, your blood pressure readings remain high or increase.
Potential side effects
  • Dizziness, lightheadedness or stomach upset may occur. If any of these effects continue or get worse, tell your medical provider or pharmacist promptly.
  • To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.
  • Remember that this medication has been prescribed because your medical provider has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not experience serious side effects.
  • This medication may cause dehydration and electrolyte imbalance, which can lead to arrhythmias. Tell your medical provider right away if you have any symptoms of dehydration or electrolyte imbalance, including:

    • Extreme thirst
    • Very dry mouth
    • Muscle cramps
    • Weakness
    • Fast or irregular heartbeat
    • Confusion
    • Chest pain
    • Shortness of breath
    • Weakness
    • Lightheadedness
    • Passing out 
  • Tell your medical provider right away if you have any serious side effects, including fainting, toe or joint pain or signs of kidney problems (such as change in amount of urine).
  • Get medical help right away if you have any very serious side effects, including decrease in vision or eye pain.
  • A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

    • Rash
    • Itching or swelling, especially of the face/tongue/throat
    • Severe dizziness
    • Trouble breathing
  • This is not a complete list of possible side effects. If you notice other effects not listed above, request a callback for medical advice. You may also report side effects to the FDA at 1-800-FDA-1088 or at

Precautions to be aware of
  • Before taking Chlorthalidone, tell your medical provider or pharmacist if you are allergic to it, or if you have any other allergies, such as an allergy to sulfonamides ("sulfa"). This product may contain inactive ingredients, which can cause allergic reactions or other problems. Go to your patient dashboard and request a medical provider callback for more details.
  • Before using this medication, tell your medical provider or pharmacist your medical history, especially of:

    • Adrenal insufficiency (Addison's disease)
    • Glaucoma or other eye issues
    • High cholesterol/triglycerides
    • Kidney disease
    • Liver disease
    • Gout
    • Lupus
    • Parathyroid disease
    • An untreated mineral imbalance, such as low potassium
  • This drug may make you dizzy, which can be exacerbated by alcohol or marijuana (cannabis). Do not drive, use machinery or do anything that requires alertness until you can do it safely. Limit alcoholic beverages. Talk to your medical provider if you are using marijuana.
  • Too much sweating, diarrhea or vomiting may cause dehydration and increase your risk of dizziness or lightheadedness. Report prolonged diarrhea or vomiting to your medical provider. Be sure to drink enough fluids to prevent dehydration unless your medical provider directs you otherwise.
  • Before having surgery, tell your doctor or dentist about all the products you use, including prescription drugs, nonprescription drugs and herbal products.
  • If you have diabetes, this product may affect your blood sugar. Check your blood sugar regularly as directed and share the results with your medical provider. Tell your medical provider right away if you have symptoms of high blood sugar, such as increased thirst or urination. Your medical provider may need to adjust your diabetes medication, exercise program or diet.
  • This medication may reduce the potassium levels in your blood. Ask your medical provider about adding potassium to your diet. A potassium supplement may be prescribed by your medical provider.
  • This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your medical provider right away if you get sunburned or have skin blisters/redness.
  • Older adults may be more sensitive to the side effects of this product, especially dizziness.
  • During pregnancy, this medication should be used only when there is a clear need. Discuss the risks and benefits with your OB/GYN.
  • This medication passes into breast milk. Consult your OB/GYN before breastfeeding.
Drug interactions (see also “How to take Chlorthalidone” section)
  • Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions.
  • Keep a list of all the products you use—including prescription/nonprescription drugs and herbal products—and share it with your medical provider and pharmacist.
  • Do not start, stop or change the dosage of any medicines without your medical provider's approval.
  • Drugs and other substances that may interact with this drug include:

    • Allopurinol
    • Dofetilide
    • Herbal supplements
    • Licorice
    • Lithium 
    • Some antidepressants
    • Some antipsychotic medications
    • Some diabetes medications
    • Some heart medications
    • Some vitamins/supplements
    • Steroids
  • Some products have ingredients that could raise your blood pressure or worsen your heart failure. Tell your pharmacist what products you are using, and ask how to use them safely—especially cough-and-cold products, diet aids or NSAIDs such as Ibuprofen or Naproxen.
  • This product may interfere with certain laboratory tests—including parathyroid and protein-bound iodide tests—possibly causing false test results. Make sure laboratory personnel and all your medical providers know you use this drug.
What to do in the event of an overdose

Symptoms of overdose may include severe dizziness or fainting.

If someone has overdosed and has serious symptoms—such as passing out or trouble breathing—call 911. If symptoms from taking this medication are less severe, call your local poison control center at 1-800-222-1222 right away.

Additional notes
  • Do not share this medication with others.
  • Lifestyle changes that may help this medication work better include stress reduction programs, exercise and dietary changes. Talk to your medical provider or pharmacist about lifestyle changes that might benefit you.
  • Laboratory and/or medical tests—including kidney function and blood mineral levels such as potassium—should be performed periodically to monitor your progress or check for side effects. Consult your medical provider for more details.
  • Check your blood pressure regularly while taking this medication. Learn how to monitor your own blood pressure at home, and share the results with your medical provider.
What to do if you miss a dose

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

How to store this medication
  • Store at room temperature away from light and moisture. Do not store in the bathroom.
  • Keep all medications away from children and pets.
  • Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details.
Treatment for
Generic Name
Drug Class
Diuretic (water pill)

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