Chlorthalidone (Oral)

Predominantly used to treat hypertension, Chlorthalidone is prescribed to patients with symptomatic or asymptomatic high blood pressure.


Chlorthalidone works in a similar way to thiazide drugs and helps to treat high blood pressure. As well as helping to reduce blood pressure, Chlorthalidone reduces the build-up of fluid caused by other conditions.

Although many patients don't display any symptoms when they have high blood pressure, it can increase their risk of developing additional conditions. Hypertension has been associated with increased risk of stroke, heart attacks and heart failure, so it's vital that the condition is treated as quickly as possible.

By relaxing the walls of the blood vessels, Chlorthalidone enables blood to pass around the body more easily and reduces the patient's blood pressure as a result.

If patients do experience symptoms of high blood pressure, they may complain of dizziness, fatigue, nausea, headaches, vision problems and they may describe a pulsating sensation in their neck and head. If Chlorthalidone is used to redcue the patient's high blood pressure, these symptoms should resolve and the patient's risk of strokes and heart problems should decrease.

As well as being used to treat high blood pressure, Chlorthalidone can be used to reduce the build-up fluid in the patient's body. As a diuretic, Chlorthalidone ensures that the body expels excess fluid via increased urination.

Although fluid retention may not sound like a particularly dangerous condition, it can be caused by complicated medical issues and it can have a debilitating effect on the patient. Conditions, such as congestive heart failure or kidney disease, can lead to a build-up of fluid on the body, also known as edema.

Swollen ankles are normally indicative of edema, particularly if the patient has existing health issues. In many cases, however, the fluid can accumulate in the abdomen or around the heart and/or lungs. Due to this, patients may have trouble breathing or experience breathlessness if edema is left untreated.

When Chlorthalidone is prescribed, it will affect the way the kidneys filter urine from the patient's blood. By preventing chloride and sodium from being reabsorbed, Chlorthalidone makes more fluid available for urination. The body stores fluid to ensure that there is the correct ratio of water and sodium in the body. If more sodium is excreted, larger amounts of water also leave the body.

This means that Chlorthalidone effectively reduces the build-up of excess fluid in the patient's body and resolves the symptoms associated with edema. Whether excess fluid is a symptom of a larger health problem or has presented in isolation, Chlorthalidone can be used to treat the issue.

Conditions Treated

Type of Medicine

  • Thiazide-like diuretic

Side Effects

When taking prescription medications, including Chlorthalidone, it's not unusual for patients to experience some side-effects. In most cases, these side-effects are not severe and are likely to decrease as the patient gets used to the medication. If the patient experiences these side-effects when taking Chlorthalidone, they may want to seek medical advice:

  • Cramps or regular cramping
  • Lack of interest in sexual intercourse
  • Hives
  • Feeling of constant movement of surroundings or self
  • Difficulty in passing stool
  • Muscle spasm
  • Inability to become aroused or keep an erection
  • Skin discoloration and/or redness
  • Loss in sexual desire, ability, performance or drive
  • Restlessness
  • Sunburn
  • Spinning sensation
  • Weakness

The above side-effects are not uncommon when taking Chlorthalidone, however, so patients may only want to seek medical help if they feel the side-effects are affecting them significantly or if they are having an adverse effect on their everyday functioning.

There are some side-effects which may need medical intervention or monitoring, however. In some cases, side-effects can indicate that the medicine isn't working as it should or that it simply isn't suited to the patient's need. If individuals experience the following adverse effects when taking Chlorthalidone, they should seek medical help:

  • Stomach or abdominal pain
  • Tarry or black stools
  • Loosening, peeling or blistering of the skin
  • Bloating
  • Blurred vision
  • Hoarseness or coughing
  • Crawling, burning, pricking, numbness, "pins and needles", tingling or itching
  • Irritated or bleeding gums
  • Chest pain
  • Cold sweats
  • Chills
  • Blood in stools or urine
  • Clay or light colored stools
  • Confusion
  • Diarrhea
  • Constipation
  • Coughing blood
  • Fatigue
  • Increased pulse
  • Faintness, lightheadedness and/or dizziness, particularly when patient gets up suddenly from lying down or sitting
  • Dry mouth
  • Headache
  • Fever
  • Dry, flushed skin skin
  • General feelings of weakness and/or tiredness
  • Fruity breath odor
  • Itching
  • Side pain
  • Increase in hunger
  • Nausea
  • Muscle pain
  • Difficulty in urinating
  • Sweating
  • Increase in thirst
  • Pains in abdomen and/or stomach or side, sometimes radiating to the back
  • Urine sugar levels increased
  • pinpoint red spots on skin
  • Irritated, red eyes
  • Increase in frequency of urination
  • Lesions on the skin which are red in color, sometimes with a purple center
  • Itching, soreness or redness of the skin
  • Indigestion
  • Shortness of breath
  • Joint swelling and/or pain
  • Rash on the skin
  • Stiffness of the joints
  • Sore throat
  • Lack of appetite
  • White spots in mouth or on lips
  • Blisters, welts, hives and/or sores
  • Pain in lower back
  • Swelling in the lower legs and/or feet
  • Unusual weight loss
  • Swelling of the glands
  • Chest tightness
  • Painful urination
  • Yellowing of the skin and/or eyes
  • Difficulty breathing
  • Unpleasant breath odor
  • Wheezing
  • Unusual bruising and/or bleeding
  • Vomiting which may contain blood

If patients experience side-effects when taking Chlorthalidone, or any other type of prescription medication, they are able to report them to the Food and Drug Administration, if they want to do so. Patients can contact the FDA on 1-800-FDA-1088 in order to report side-effects associated with Chlorthalidone. However, if patients require help due to the medication's side-effects, they should contact their physician or, in emergency situations, call 911 for medical assistance.


When taking Chlorthalidone, it's essential that patient's follow their doctor's treatment advice. Patients will be given specific instructions regarding the appropriate dose of Chlorthalidone and when they should take the medication. This advice will reflect the patient's condition and medical history so it's important that patient's adhere to the unique treatment regime they're prescribed.

There are, however, general dosing guidelines when it comes to the use of Chlorthalidone. If patients are being treated with Chlorthalidone due to high blood pressure, a standard dose of 25mg once per day may be appropriate. Alternatively, if patients are given Chlorthalidone due to fluid retention, they may be prescribed a dose of 50-100mg per day or 100mg every other day.

Although children can be prescribed Chlorthalidone for both high blood pressure and/or fluid retention, there are no standard dosing instructions for young people. In most cases, the appropriate dose will depend on the child's weight and condition. Physicians will determine whether treatment with Chlorthalidone is suitable and, if so, what dose is appropriate.

Patients are usually advised to take Chlorthalidone with food, in the morning. This is a general guideline, however, and patients should seek confirmation of when to take their medication from their physician.

If patients miss a dose of Chlorthalidone, they should take their medication as soon as they remember to do so. Double doses of Chlorthalidone should not be taken so, if the next dose is almost due, patients should skip the missed dose completely.

If patients are unsure how to take Chlorthalidone, they should seek medical advice from their physician or pharmacist.

Potential Drug Interactions

Most medications can interact with each other if they are taken at the same. In some cases, it may not be appropriate for patients to take differing medications, even if they have symptoms of a specific medical condition.

Although the use of Chlorthalidone with the following medications is not usually recommended, doctors may choose to proceed with treatment in some circumstances:

  • Aceclofenac
  • Aspirin
  • Acemetacin
  • Arsenic Trioxide
  • Acetyldigoxin
  • Bepridil
  • Amtolmetin Guacil
  • Bromfenac
  • Clonixin
  • Bufexamac
  • Deslanoside
  • Celecoxib
  • Dexibuprofen
  • Choline Salicylate
  • Dexketoprofen
  • Ibuprofen
  • Diclofenac
  • Flufenamic Acid
  • Diflunisal
  • Floctafenine
  • Digitalis
  • Flecainide
  • Digitoxin
  • Feprazole
  • Digoxin
  • Fepradinol
  • Dipyrone
  • Fenoprofen
  • Dofetilide
  • Felbinac
  • Droperidol
  • Etoricoxib
  • Droxicam
  • Etodolac
  • Ketanserin
  • Etofenamate
  • Flurbiprofen
  • Ketoprofen
  • Indomethacin
  • Ketorolac
  • Meclofenamate
  • Levomethadyl
  • Lumiracoxib
  • Lithium
  • Loxoprofen
  • Lornoxicam
  • Mefenamic Acid
  • Piroxicam
  • Meloxicam
  • Piketoprofen
  • Metildigoxin
  • Phenylbutazone
  • Morniflumate
  • Parecoxib
  • Nabumetone
  • Oxyphenbutazone
  • Naproxen
  • Oxaprozine
  • Nepafenac
  • Nimesulide
  • Niflumic Acid
  • Nimesulide Beta Cyclodextrin
  • Proglumetacin
  • Valdecoxib
  • Propyphenazone
  • Tolmetin
  • Sotalol
  • Proquazone
  • Tolfenamic Acid
  • Rofecoxib
  • Tiaprofenic Acid
  • Salicylic Acid
  • Tenoxicam
  • Salsalate
  • Sulindac
  • Sodium Salicylate

If Chlorthalidone is prescribed in conjunction with any of the above medications, doctors may change the dose of the medications and/or advise patients to take the medicines at different times.

If patients take Chlorthalidone alongside the following medications or supplements, they may be more at risk of experiencing side-effects:

  • Gossypol
  • Warfarin
  • Licorice

If patients experience severe side-effects whilst receiving treatment, they should inform their physician. If the side-effects are intolerable, doctors may alter the treatment plan in order to provide relief from unpleasant and unwanted side-effects.

Although medications can interact with one another, they can also interact with vitamins and herbal supplements. Due to this, patients should ensure that their doctor is aware of any medications, vitamins and supplements they are taking, including over-the-counter medication.

Similarly, if patients purchase over-the-counter medications, supplements or vitamins, they should seek medical advice from a doctor or pharmacist first and inform the relevant practitioner that they are also taking Chlorthalidone.


As Chlorthalidone is a diuretic, it can increase the frequency of urination. When treating edema, this can be a sign that the medication is working as it helps to rid the body of excess fluid. Although an increase in the frequency of urination is normal when taking Chlorthalidone, patients should seek medical advice if they are concerned about the symptoms they are experiencing.

Patients who are unable to form urine, a condition known as anuria, should not be treated with Chlorthalidone.

If patients have been diagnosed with liver or kidney disease, Chlorthalidone should be prescribed with caution. These conditions can make it more difficult for the body to break down and metabolize medications. As a result, patients may require a lose dose of Chlorthalidone, if treatment with this medication is deemed appropriate.

Patients with the following conditions may not be suitable for treatment with Chlorthalidone:

  • Gout
  • High levels of uric acid in the blood (Hyperuricemia)
  • Low levels of phosphorus in the blood (Hypophosphatemia)
  • Low levels of magnesium in the blood (Hypomagnesemia)
  • Asthma
  • High levels of calcium in the blood (Hypercalcemia)
  • Systemic lupus erythematosus
  • Low levels of chloride in the blood (Hypochloremia)
  • Diabetes
  • Low levels of potassium in the blood (Hypokalemia)
  • Low levels of sodium in the blood (Hyponatremia)

If patients with the above conditions are treated with Chlorthalidone, they may require a non-standard dose of the medication and they may also warrant an increased level of monitoring.

If pregnant patients take Chlorthalidone, there is a risk that the medication could affect the fetus. In some cases, Chlorthalidone could cause jaundice to occur in the fetus or a newborn. Due to this, Chlorthalidone is not usually given to pregnant women, unless it is deemed necessary. If pregnant patients are prescribed Chlorthalidone, they should discuss the potential risks with their physician before taking the medication.

If patients become pregnant when taking prescription medication, such as Chlorthalidone, they should contact their doctor for medical advice.

Chlorthalidone can also affect milk production and may, therefore, limit a patient's ability to breastfeed. Although some medical organizations deem thiazide drugs to be safe for breastfeeding mothers, not all doctors are willing to prescribe Chlorthalidone if patients are currently breastfeeding. If patients are nursing an infant, or planning to do so, they should discuss any potential risks with their doctor before taking Chlorthalidone.

When taking Chlorthalidone, some patients may experience dizziness. If affected, patients should not drive or operate heavy machinery until the dizziness has passed.

Consuming alcohol when taking Chlorthalidone can make certain side-effects, such as dizziness, worse. Patients should avoid alcohol or limit their intake if they are taking Chlorthalidone or similar medication.

When taking Chlorthalidone, patients should undergo regular blood tests to ensure that the medication is working correctly.

In some patients, Chlorthalidone could lead to a lack of potassium in the blood. This can be associated with the following symptoms:

  • Seizures or convulsions
  • Increase in heart rate
  • Vomiting or nausea
  • Decrease in urine output
  • Sleepiness
  • Increased thirst
  • Dry mouth
  • Muscle cramping or pain

If patients notice these side-effects occurring, they should seek medical help and confirm that they are not suffering from hypokalemia (low potassium levels).

If patients develop an allergic reaction when taking Chlorthalidone, they must seek urgent medical assistance. Allergic reactions may include difficulty breathing, hives and/or swelling of the face, lips or throat.


When patients are prescribed Chlorthalidone, they are normally advised to keep the medication at home. Unless otherwise instructions, patients should keep Chlorthalidone at room temperature and in a location which is out of direct sunlight and free from moisture and heat.

In addition to this, patients should keep their medicine in a secure location which cannot be accessed by children or pets, if they are present in the home.

If patients are told to stop taking Chlorthalidone or if the medication expires, patients should seek help from a pharmacist or physician when disposing of the drug.


When patients first start to develop high blood pressure and/or fluid retention, they may not notice any symptoms occurring. Over time, however, symptoms, such as breathlessness, dizziness, and palpitations can occur.

In addition to this, patients may develop an increased risk of other serious medical problems, if hypertension or fluid retention is left untreated. By prescribing Chlorthalidone, physicians can help to lower the patient's blood pressure and remove any excess fluid from their body. As well as reducing the risk of future health problems, Chlorthalidone should help reduce any symptoms the patient is experiencing.

If Chlorthalidone is prescribed to treat hypertension, patients should be aware that it will not provide a cure to high blood pressure. Although the medication will help to manage the condition, it should often be taken in conjunction with lifestyle changes. Doctors may advise the patient to cut out certain foods from their diet or increase the amount of exercise they do, for example.

If patients follow their physician's advice regarding their lifestyle and diet, as well as taking Chlorthalidone as they are instructed to do so, they can successfully reduce their blood pressure and/or levels of fluid retention.

Last Reviewed:
December 24, 2017
Last Updated:
April 04, 2018
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