Hydrochlorothiazide, Oral Tablet

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on September 24, 2015Written by University of Illinois-Chicago, Drug Information Group

Important warnings

  • Fluids/electrolytes warning: Your doctor should check your fluid and electrolytes when 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
  • Sulfonamide allergy warning: If you’re allergic to medications that contain sulfonamide, you shouldn’t take this drug.
  • 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. If left untreated, it can lead to permanent vision loss. If you have blurred vision, it may return to normal after you stop taking this medication.

What is hydrochlorothiazide?

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

Hydrochlorothiazide is available as the brand-name drug Microzide. It’s also available as a generic drug. Generic drugs usually cost less. In some cases, they may not be available in every strength or form as the brand-name version.

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 certain medications (corticosteroids or estrogens). It may also help treat swelling that’s caused by kidney problems.

This drug may be used alone. If you have a severe form of high blood pressure, it may be used with other drugs.

How it works

Hydrochlorothiazide belongs to a class of drugs called thiazide diuretics. A class of drugs refers to medications that work similarly. They have a similar chemical structure and 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 keeps your heart from working as hard to pump blood. This lowers high blood pressure levels and reduces swelling.

Hydrochlorothiazide side effects

Hydrochlorothiazide oral tablet doesn’t cause drowsiness but it can cause other side effects.

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
  • trouble getting or keeping an erection (erectile dysfunction)
  • tingling in your hands, legs, and feet

If these effects are mild, they 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

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Hydrochlorothiazide may interact with other medications

Hydrochlorothiazide oral tablet can interact with other medications, herbs, or vitamins you might be taking. That’s why your doctor should manage all of your medications carefully. If you’re curious about how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Note: You can reduce your chances of drug interactions by having all of your prescriptions filled at the same pharmacy. That way, a pharmacist can check for possible drug interactions.

Examples of drugs that can cause interactions with hydrochlorothiazide are listed below.

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 standing up after sitting or lying down. Examples of these drugs include:

  • phenobarbital
  • primidone
  • pentobarbital

Bipolar disorder drug

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 lithium toxicity.

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 drugs

These drugs may make hydrochlorothiazide less effective. This means it may not work as well to treat your blood pressure or swelling. Examples of these drugs include:

  • cholestyramine
  • colestipol

Corticosteroids

Taking these drugs with hydrochlorothiazide can cause further electrolyte loss (especially potassium). This can lead to medical problems. 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:
    • exenatide
    • 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 standing up after sitting or lying down. Examples of these drugs include:

  • morphine
  • codeine

Pain drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) can make hydrochlorothiazide less effective. This means that 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

Skeletal muscle relaxants

Taking these drugs with hydrochlorothiazide may increase the effects of the muscle relaxants. This could lead to more side effects. An example of these drugs is:

  • tubocurarine

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

Hydrochlorothiazide warnings

This drug comes with several warnings.

Allergy warning

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

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

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

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 standing 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 take you off of 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.

How to take hydrochlorothiazide

All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

Forms and strengths

Generic: hydrochlorothiazide

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

Brand: Microzide

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

Dosage for high blood pressure

Adult dosage (ages 18–64 years)

  • The starting dosage is 25 mg taken by mouth once per day.
  • Your doctor may increase your dosage to 50 mg per day if your blood pressure stays high.

Child dosage (ages 12–17 years)

  • The starting dosage is 25 mg taken by mouth once per day.
  • Your doctor may increase your child’s dosage to 50 mg per day if your child’s blood pressure stays high.

Child dosage (ages 3–11 years)

The usual dosage is 0.5–1 mg per pound per day, taken in a single dose or two divided doses. The dosage per day shouldn’t be more than 100 mg.

Child dosage (ages 6 months–2 years)

The usual dosage is 0.5–1 mg per pound per day, taken in a single dose or two divided doses. The dosage per day shouldn’t be more than 37.5 mg.

Child dosage (ages 0–6 months)

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 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.

Dosage for edema

Adult dosage (ages 18–64 years)

  • The usual dosage is 25–100 mg each day, taken by mouth as a single or divided dose.
  • Many people respond to intermittent therapy. This means that you may need to take this drug every other day or for 3–5 days each week. Taking the drug this way lowers your risk of an imbalance in your electrolytes.

Child dosage (ages 12–17 years)

  • The usual dosage is 25–100 mg each day, taken by mouth as a single or divided dose.
  • Many people respond to intermittent therapy. This means your child may need to take this drug every other day or for 3–5 days each week. Taking the drug this way lowers your child’s risk of an imbalance in their electrolytes.

Child dosage (ages 3–11 years)

The usual dosage is 0.5–1 mg per pound per day, taken in a single dose or two divided doses. The dosage per day shouldn’t be more than 100 mg.

Child dosage (ages 6 months–2 years)

The usual dosage is 0.5–1 mg per pound per day, taken in a single dose or two divided doses. The dosage per day shouldn’t be more than 37.5 mg.

Child dosage (ages 0–6 months)

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 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.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.

Take as directed

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

If you 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 it 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 don't take it on schedule

Your swelling can increase and your blood pressure might rise. High blood pressure raises your risk of heart attack or stroke.

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 local poison control center. 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

If this drug is working, your blood pressure may be lower or the swelling in your legs and feet may 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 diary with you to your doctor appointments.

Important considerations for taking hydrochlorothiazide

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.
  • The generic form of this drug is usually stocked at pharmacies. However, the brand-name version might not be stocked at every pharmacy. If your doctor prescribed the brand-name version of this drug, call ahead when refilling your prescription.

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 hurt your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled box 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 diary with you to your checkups.

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.

Are there any alternatives?

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.

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