1. Hydrochlorothiazide oral tablet is only available as a generic drug.
  2. Hydrochlorothiazide comes as a tablet or capsule that you take by mouth.
  3. Hydrochlorothiazide oral tablet is used to treat high blood pressure, and swelling caused by heart failure, liver damage, and certain medications.

Hydrochlorothiazide is a prescription drug. It comes as a tablet or capsule that you take by mouth.

Hydrochlorothiazide oral tablet is available in a generic form only. Generic drugs usually cost less than brand-name drugs.

Why it’s used

Hydrochlorothiazide is used to treat high blood pressure. It’s also used to treat swelling that’s caused by heart failure, liver damage (cirrhosis), and taking medications called corticosteroids or estrogens. It may also help treat swelling that’s caused by kidney problems.

This drug may be used alone or in combination with other drugs.

How it works

Hydrochlorothiazide belongs to a class of drugs called thiazide diuretics. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

It isn’t known exactly how hydrochlorothiazide works. It’s thought that it works to remove excess salt and water from your body. This action keeps your heart from working as hard to pump blood, which lowers blood pressure and reduces swelling.

Hydrochlorothiazide can cause mild or serious side effects. The following list contains some of the key side effects that may occur while taking hydrochlorothiazide. This list does not include all possible side effects.

For more information on the possible side effects of hydrochlorothiazide, or tips on how to deal with a troubling side effect, talk with your doctor or pharmacist.

More common side effects

The more common side effects that can occur with hydrochlorothiazide include:

  • blood pressure that’s lower than normal (especially when standing up after sitting or lying down)
  • dizziness
  • headache
  • weakness
  • erectile dysfunction (trouble getting or keeping an erection)
  • tingling in your hands, legs, and feet

These effects may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • severe skin reactions such as Stevens-Johnson syndrome and exfoliative dermatitis, with symptoms such as:
    • painful skin rash
    • skin peeling and blisters
    • fever
    • mouth sores
  • kidney failure, with symptoms such as:
    • weakness
    • shortness of breath
    • tiredness
    • confusion
    • abnormal heart rate or chest pain
    • producing less urine than normal
    • increased swelling in your legs, ankles, or feet
  • blurred vision, with symptoms such as:
    • eye pain
    • trouble seeing

Hydrochlorothiazide oral tablet can interact with several other medications. Different interactions can cause different effects. For instance, some can interfere with how well a drug works, while others can cause increased side effects.

Below is a list of medications that can interact with hydrochlorothiazide. This list does not contain all drugs that may interact with hydrochlorothiazide.

Before taking hydrochlorothiazide, be sure to tell your doctor and pharmacist about all prescription, over-the-counter, and other drugs you take. Also tell them about any vitamins, herbs, and supplements you use. Sharing this information can help you avoid potential interactions.

If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.

Barbiturates

If you take these drugs with hydrochlorothiazide, your blood pressure may be lowered too much. You may have symptoms such as feeling dizzy when you stand up after sitting or lying down. Examples of these drugs include:

  • phenobarbital
  • pentobarbital

Lithium

In general, lithium shouldn’t be taken with hydrochlorothiazide. That’s because hydrochlorothiazide slows the clearance of lithium from your body. This increases your risk of high levels of lithium in your body, which can cause dangerous side effects.

Blood pressure drugs

Taking hydrochlorothiazide with other blood pressure medications can make your blood pressure drop too low. Examples of these drugs include:

  • angiotensin-converting enzyme (ACE) inhibitors, such as:
    • lisinopril
    • fosinopril
    • enalapril
  • angiotensin receptor blockers (ARBs), such as:
    • losartan
    • valsartan
    • candesartan
  • beta-blockers, such as:
    • atenolol
    • metoprolol
    • bisoprolol
  • calcium channel blockers, such as:
    • amlodipine
    • verapamil
    • diltiazem

Cholesterol-lowering drugs

Taking hydrochlorothiazide with certain drugs that lower cholesterol levels may make hydrochlorothiazide less effective. This means it may not work as well to treat your blood pressure or swelling. Examples of these cholesterol drugs include:

  • cholestyramine
  • colestipol

Corticosteroids

Hydrochlorothiazide can lower your electrolyte levels. Taking corticosteroids with hydrochlorothiazide can cause further loss of electrolytes (especially potassium). Low potassium levels can lead to constipation, fatigue, muscle breakdown, and weakness. Examples of these drugs include:

  • prednisone
  • methylprednisolone

Diabetes drugs

Hydrochlorothiazide can cause high blood sugar levels. If you take hydrochlorothiazide with diabetes drugs, your doctor may increase your dosage of your diabetes medications. Examples of these drugs include:

  • insulin
  • oral diabetes drugs, such as:
    • metformin
    • glimepiride
    • pioglitazone
    • sitagliptin

Narcotics

Taking hydrochlorothiazide with narcotics can make your blood pressure drop too low. You may have symptoms such as feeling dizzy when you stand up after sitting or lying down. Examples of these drugs include:

  • morphine
  • codeine

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Taking NSAIDs with hydrochlorothiazide can make hydrochlorothiazide less effective. This means it may not work as well to treat your blood pressure or swelling.

If you’re taking an NSAID with hydrochlorothiazide, your doctor will closely monitor you. Examples of these drugs include:

  • ibuprofen
  • naproxen

Muscle relaxant

Taking hydrochlorothiazide with tubocurarine, a muscle relaxant, may increase the effects of tubocurarine. This could lead to more side effects.

The hydrochlorothiazide dosage your doctor prescribes will depend on several factors. These include:

  • the type and severity of the condition you’re using hydrochlorothiazide to treat
  • your age
  • the form of hydrochlorothiazide you take
  • other medical conditions you may have, such as kidney damage

Typically, your doctor will start you on a low dosage and adjust it over time to reach the dosage that’s right for you. They’ll ultimately prescribe the smallest dosage that provides the desired effect.

The following information describes dosages that are commonly used or recommended. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to suit your needs.

Forms and strengths

Generic: Hydrochlorothiazide

  • Form: oral tablet
  • Strengths: 12.5 mg, 25 mg, and 50 mg

Dosage for high blood pressure

Adult dosage (ages 18 to 64 years)

  • Typical starting dosage: 25 mg taken by mouth once per day.
  • Dosage increases: If your blood pressure stays high, your doctor may increase your dosage to 50 mg per day given as a single or two divided doses.

Child dosage (ages 12 to 17 years)

  • Typical starting dosage: 25 mg taken by mouth once per day.
  • Dosage increases: If your child’s blood pressure stays high, their doctor may increase your child’s dosage to 50 mg per day given as a single dose, or as two divided doses.

Child dosage (ages 3 to 11 years)

  • Typical dosage: 0.5 to 1 mg per pound per day, taken in a single dose or two divided doses.
  • Maximum daily dosage: 100 mg.

Child dosage (ages 6 months to 2 years)

  • Typical dosage: 0.5 to 1 mg per pound per day, taken in a single dose or two divided doses.
  • Maximum daily dosage: 37.5 mg.

Child dosage (ages 0 to 6 months)

  • Typical dosage: The usual dosage is up to 1.5 mg per pound per day, taken by mouth in two divided doses.

Senior dosage (ages 65 years and older)

There are no specific recommendations for senior dosing. Older adults may process drugs more slowly. A normal adult dosage may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dosage or a different dosing schedule.

Dosage for edema

Adult dosage (ages 18 to 64 years)

  • Typical dosage: 25 to 100 mg each day, taken by mouth as a single or divided dose.
  • Intermittent therapy: Many people respond to intermittent therapy. This means that you may need to take this drug every other day or for three to five days each week. Taking the drug this way lowers your risk of an imbalance in your electrolytes.

Child dosage (ages 12 to 17 years)

  • Typical dosage: 25 to 100 mg each day, taken by mouth as a single or divided dose.
  • Intermittent therapy: Many people respond to intermittent therapy. This means your child may need to take this drug every other day or for three to five days each week. Taking the drug this way lowers your child’s risk of an imbalance in their electrolytes.

Child dosage (ages 3 to 11 years)

  • Typical dosage: The usual dosage is 0.5 to 1 mg per pound per day, taken in a single dose or two divided doses.
  • Maximum daily dosage: 100 mg.

Child dosage (ages 6 months to 2 years)

  • Typical dosage: 0.5 to 1 mg per pound per day, taken in a single dose or two divided doses.
  • Maximum daily dosage: 37.5 mg.

Child dosage (ages 0 to 6 months)

  • Typical dosage: Up to 1.5 mg per pound per day, taken by mouth in two divided doses.

Senior dosage (ages 65 years and older)

There are no specific recommendations for senior dosing. Older adults may process drugs more slowly. A normal adult dosage may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dosage or a different dosing schedule.

This drug comes with several warnings.

Fluid and electrolyte imbalance warning

Your doctor should check your fluid and electrolyte levels while you’re taking hydrochlorothiazide. This drug can cause a fluid or electrolyte imbalance. Symptoms can include:

  • dry mouth
  • thirst
  • weakness
  • tiredness
  • restlessness
  • confusion
  • seizures
  • muscle pain or cramps
  • muscle fatigue
  • lower than normal blood pressure
  • higher than normal heart rate
  • producing less urine than normal
  • nausea or vomiting

Vision problems warning

Hydrochlorothiazide can cause blurred vision and glaucoma. Symptoms include eye pain and trouble seeing. These problems often occur within hours to weeks after starting this medication.

Tell your doctor if you have any vision problems while taking this drug. If you have blurred vision, it may return to normal after you stop taking this medication. However, if left untreated, certain vision problems can lead to permanent vision loss.

Sulfonamide allergy warning

If you’re allergic to medications that contain sulfonamide, you shouldn’t take this drug.

Allergy warning

Hydrochlorothiazide can cause a severe allergic reaction. Symptoms can include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

Alcohol warning

Drinking alcohol while taking hydrochlorothiazide can make your blood pressure drop too low. You may have symptoms such as feeling dizzy when you stand up after sitting or lying down.

Warnings for people with certain health conditions

For people with kidney problems: Use caution when taking hydrochlorothiazide if you have poor kidney function. This drug is cleared from your body by your kidneys. If your kidneys don’t work as well, this drug may build up in your body and cause more side effects. If your kidney function gets worse, your doctor might stop your treatment with this medication.

For people with kidneys that don’t make enough urine: You can’t take hydrochlorothiazide if your kidneys can’t make enough urine. This drug can cause electrolyte and fluid loss, which may make you produce even less urine.

For people with poor liver function: Use this drug with caution if you have poor liver function or progressive liver disease. Hydrochlorothiazide can cause electrolyte and fluid imbalance. This can make your liver function worse.

For people with lupus: This drug can cause your lupus to flare up.

Warnings for certain groups

For pregnant women: Hydrochlorothiazide is a category B pregnancy drug. That means two things:

  1. Research in animals hasn’t shown a risk to the fetus when the mother takes the drug.
  2. There aren’t enough studies done in humans to show if the drug poses a risk to the fetus.

Talk to your doctor if you’re pregnant or planning to become pregnant. Animal studies don’t always predict the way humans would respond. Therefore, this drug should only be used in pregnancy if clearly needed.

For women who are breastfeeding: Hydrochlorothiazide may pass into breast milk and may cause side effects in a child who is breastfed. Talk to your doctor if you breastfeed your baby. You may need to decide whether to stop breastfeeding or stop taking this medication.

For seniors: Older adults may process drugs more slowly. A normal adult dose may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dose or a different schedule.

Hydrochlorothiazide is used for long-term treatment. It comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug or don’t take it at all: Your swelling and high blood pressure might get worse. High blood pressure raises your risk of heart attack or stroke.

If you stop taking the drug suddenly, your swelling can increase and your blood pressure might increase rapidly. High blood pressure raises your risk of heart attack or stroke.

If you miss doses or don’t take the drug on schedule: Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much: If you take too much hydrochlorothiazide, your blood pressure might drop too low. You might feel faint or dizzy.

If you think you’ve taken too much of this drug, call your doctor or seek guidance from the American Association of Poison Control Centers at 800-222-1222 or through their online tool. But if your symptoms are severe, call 911 or go to the nearest emergency room right away.

What to do if you miss a dose: If you forget to take your dose, take it as soon as you remember. If it’s just a few hours until the time for your next dose, then wait and only take one dose at that time. Never try to catch up by taking two doses at once. This could cause dangerous side effects.

How to tell if the drug is working: Your blood pressure should be lower or the swelling in your legs and feet should get better.

Your doctor will monitor your blood pressure at your checkups. You can also check your blood pressure at home. Keep a log with the date, time of day, and your blood pressure readings. Bring this log with you to your doctor appointments.

Keep these considerations in mind if your doctor prescribes hydrochlorothiazide for you.

General

  • You can take hydrochlorothiazide with or without food.
  • Take this drug in the morning, not the evening. This drug may make you urinate more. Taking it in the evening can make you need to get up at night to use the bathroom.
  • You can crush hydrochlorothiazide tablets.

Storage

  • Store hydrochlorothiazide at a temperature between 68°F and 77°F (20°C and 25°C).
  • Keep this drug away from light.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t harm your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Self-management

You may need to check your blood pressure at home. You should keep a log with the date, time of day, and your blood pressure readings. Bring this log with you to your checkups.

Shop for blood pressure monitors.

Clinical monitoring

During treatment with this drug, your doctor may check your potassium levels. This will help make sure you don’t have any imbalances.

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.