If you have high blood pressure, your doctor may prescribe hydrochlorothiazide. It’s a prescription drug that’s used in adults with this condition.

Hydrochlorothiazide can also be used to help treat edema (water retention) that’s caused by another medical condition. These conditions include heart failure and kidney disease.

Hydrochlorothiazide may also be used in some children with these conditions. And for some of its uses, a doctor may recommend it together with other medications.

For more information about how hydrochlorothiazide is used, see the “What is hydrochlorothiazide used for?” section below.

Hydrochlorothiazide oral tablet basics

Hydrochlorothiazide is classified as a diuretic. It’s also sometimes called a water pill. (A drug’s classification refers to the group of drugs it belongs to.)

This medication comes as tablets that you’ll swallow.

Note: Hydrochlorothiazide also comes in an oral capsule form. But only oral tablets are described in this article. If you’d like to learn about hydrochlorothiazide’s other forms, talk with your doctor or pharmacist.

Hydrochlorothiazide oral tablet brand-name versions

Hydrochlorothiazide tablets are a generic medication. They aren’t available in a brand-name version.

Note: The other forms of hydrochlorothiazide have different brand-name drug versions. Talk with your doctor or pharmacist to learn more.

Hydrochlorothiazide oral tablet is a generic drug, which means it’s an exact copy of the active drug in a brand-name medication. The brand-name medication that hydrochlorothiazide oral tablet is based on is no longer available.

Generic drugs are thought to be as safe and effective as the brand-name drug they’re based on. In general, generics usually cost less than brand-name drugs.

If you’d like to know more about the differences between generic and brand-name drugs, see this Healthline article.

Like most drugs, hydrochlorothiazide oral tablets may cause mild or serious side effects. The lists below describe some of the more common side effects this drug may cause. These lists don’t include all possible side effects.

Keep in mind that side effects of a drug can depend on:

  • your age
  • other health conditions you have
  • other medications you may be taking

Your doctor or pharmacist can tell you more about the potential side effects of hydrochlorothiazide. They can also suggest ways to help reduce side effects.

Mild side effects

Here are some of the mild side effects that hydrochlorothiazide oral tablets can cause. To learn about other mild side effects, talk with your doctor or pharmacist, or read hydrochlorothiazide oral tablet’s prescribing information.

Mild side effects of hydrochlorothiazide oral tablets that have been reported include:

Mild side effects of many drugs may go away within a few days or a couple of weeks. But if they become bothersome, talk with your doctor or pharmacist.

* For more information about this side effect, see the “Side effect focus” section below.

Serious side effects

Serious side effects from hydrochlorothiazide oral tablets can occur, but they aren’t common. If you have serious side effects from this drug, call your doctor right away. However, if you think you’re having a medical emergency, you should call 911 or your local emergency number.

Serious side effects of hydrochlorothiazide oral tablet that have been reported include:

* For more information about this side effect, see the “Side effect focus” section below.

Side effect focus

Learn more about some of the side effects hydrochlorothiazide oral tablets may cause.

Low blood pressure

You may have low blood pressure as a side effect of hydrochlorothiazide. Keep in mind that the drug is used to treat high blood pressure. So this side effect can happen if the drug works too well and lowers your blood pressure too much.

In general, blood pressure is considered too low if:

  • systolic blood pressure is below 120 millimeters of mercury (mmHg), or
  • diastolic blood pressure is below 80 mmHg

Blood pressure readings are recorded as fractions, with one number on top and one number on the bottom. Systolic blood pressure is the top number on a blood pressure reading. And diastolic blood pressure is the bottom number on the reading. To learn more about systolic versus diastolic blood pressure, see this article.

Hydrochlorothiazide can also cause a type of low blood pressure called orthostatic hypotension. With this condition, your blood pressure suddenly drops when you stand up too quickly. It can cause you to feel faint or even lose consciousness in rare cases.

Low blood pressure doesn’t always cause symptoms, but you may have:

What might help

Your doctor will probably have you monitor your blood pressure at home while you’re taking hydrochlorothiazide. Before you start taking the drug, ask your doctor what you should do if your blood pressure readings are too low.

Sometimes, mild low blood pressure can be treated by:

  • drinking more fluids
  • changing the foods you eat or how you eat them
  • altering the way you sit and stand

Another way your doctor may choose to treat low blood pressure is by adjusting your hydrochlorothiazide dosage. But if you have low blood pressure that’s severe or bothersome, they may suggest you try a different medication for your condition.

Dizziness

You may have dizziness as a side effect of hydrochlorothiazide. It’s not known if this was common or rare in people taking the drug during studies, though.

Dizziness may sometimes be a symptom of other side effects of hydrochlorothiazide. This includes low blood pressure, which is described in the section just above.

Dizziness can also be an early symptom of a rare but serious condition such as stroke or heart attack. And these conditions can happen in people with high blood pressure, which the drug is used to treat.

What might help

If you have dizziness while you’re taking hydrochlorothiazide, talk with your doctor or pharmacist. They can help determine if the drug is causing it or it’s related to another side effect of the condition you’re treating.

Your doctor may recommend that you try a lower dose of hydrochlorothiazide if they think it’s the cause of your dizziness. If dizziness is bothering you, your doctor may recommend a different medication for your condition.

Muscle spasms and cramps

You could have muscle spasms and cramps with hydrochlorothiazide. But it’s not known if these were common or rare in people taking the drug during studies.

Muscle spasms and cramps can happen as side effects of the drug. But they can also be symptoms of more serious side effects, such as an electrolyte imbalance. (With electrolyte imbalance, one or several of your electrolyte levels may be either too high or too low.)

Diuretics, including hydrochlorothiazide, can cause electrolyte imbalances as they flush water out of your body. An example of an electrolyte imbalance is a low potassium level.

What might help

Tell your doctor if you have muscle spasms or cramps while you’re taking hydrochlorothiazide. They may order lab tests to check your electrolyte levels. They may also check to make sure you’re getting enough fluids while you’re taking this drug.

If your electrolyte levels are normal and you’re having muscle spasms or cramps, your doctor may suggest trying a medication other than hydrochlorothiazide.

Allergic reaction

Some people may have an allergic reaction to hydrochlorothiazide oral tablets.

Symptoms of a mild allergic reaction can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include swelling under your skin, typically in your eyelids, lips, hands, or feet. They can also include swelling of your tongue, mouth, or throat, which can cause trouble breathing.

Call your doctor right away if you have an allergic reaction to hydrochlorothiazide oral tablets. But if you think you’re having a medical emergency, call 911 or your local emergency number.

Your doctor will explain how you should take hydrochlorothiazide. They will also explain how much to take and how often. Be sure to follow your doctor’s instructions. Below are commonly used dosages, but always take the dosage your doctor prescribes.

Taking hydrochlorothiazide oral tablet

You’ll take hydrochlorothiazide oral tablets by mouth. They’re available in the following strengths:

  • 12.5 milligrams (mg)
  • 25 mg
  • 50 mg

Dosage and when to take

How often you’ll take hydrochlorothiazide depends on the condition you’re using it to treat.

For example, in adults, when treating:

  • high blood pressure, hydrochlorothiazide oral tablets are usually taken once or twice per day.
  • edema (water retention) that’s caused by another medical condition, hydrochlorothiazide oral tablets are usually taken once or twice per day. Some people may find the drug works well when taken every other day, or 3 to 5 days per week, for this condition. Your doctor will work with you to find the best dosage for your condition.

In children, hydrochlorothiazide’s dosage is based on the child’s body weight. Your child’s doctor will recommend the dosage that’s right for their condition.

Taking hydrochlorothiazide oral tablet with other drugs

Your doctor may prescribe hydrochlorothiazide on its own for the conditions it’s approved to treat. But in some cases, they may prescribe the drug with other medications.

For example, it’s not unusual for people with high blood pressure to take more than one medication for their condition. Other blood pressure medications that may be used together with hydrochlorothiazide include:

Hydrochlorothiazide may also be prescribed together with potassium. This is because hydrochlorothiazide can cause a low potassium level as a side effect. Your doctor may have you take a potassium pill with hydrochlorothiazide to help prevent or treat this side effect.

Additionally, hydrochlorothiazide is sometimes included in combination drugs. These are medications that contain one or more active drugs in a single pill.

Combination drugs can make it easier to remember to take your medications because you have fewer pills. But combination medications are often more expensive than individual drugs.

Examples of combination drugs that contain hydrochlorothiazide include:

Your doctor or pharmacist can give you more information about combination drugs and using hydrochlorothiazide with other drugs.

Questions about taking hydrochlorothiazide oral tablet

Here’s a list of some questions related to taking hydrochlorothiazide oral tablets.

  • What if I miss a dose of hydrochlorothiazide oral tablets? If you miss a dose of hydrochlorothiazide, try and take it as soon as you remember. But if it’s nearly time for your next dose, simply skip the missed dose. You shouldn’t “double up” and take two doses at once to make up for the missed dose. Doing so can increase your risk for side effects from the drug.
  • Will I need to use hydrochlorothiazide oral tablets long term? Usually, you will take hydrochlorothiazide long term if you and your doctor agree that it’s working well for your condition.
  • Can hydrochlorothiazide oral tablets be chewed, crushed, or split? It may be OK to crush or split hydrochlorothiazide tablets. But be sure to ask your doctor or pharmacist for more information about chewing, crushing, or splitting these tablets.
  • Should I take hydrochlorothiazide oral tablets with food? Hydrochlorothiazide tablets may be taken with or without food.
  • How long do hydrochlorothiazide oral tablets take to work? Hydrochlorothiazide tablets begin working about 2 hours after you take your dose.
Questions for your doctor

You may have questions about hydrochlorothiazide oral tablets and your treatment plan. It’s important to discuss all your concerns with your doctor.

Here are a few tips that might help guide your discussion:

  • Before your appointment, write down questions like:
    • How will hydrochlorothiazide oral tablets affect my body, mood, or lifestyle?
  • Bring someone with you to your appointment if doing so will help you feel more comfortable.
  • If you don’t understand something related to your condition or treatment, ask your doctor to explain it to you.

Remember, your doctor and other healthcare professionals are available to help you. And they want you to get the best care possible. So don’t be afraid to ask questions or offer feedback on your treatment.

If you have hypertension (high blood pressure), your doctor may prescribe hydrochlorothiazide. It’s a prescription drug that’s used in adults with this condition.

With high blood pressure, the pressure inside your blood vessels is higher than normal. This can make your heart work harder than it should to pump blood throughout your body.

Hydrochlorothiazide is also used to help treat edema (water retention) that’s caused by another medical condition. These conditions include heart failure and kidney disease.

With edema, you have fluid buildup in your body. Edema can be caused by other health conditions, such as problems with your heart or kidneys or taking certain medications, including estrogen.

For edema and blood pressure treatment, hydrochlorothiazide may be used in adults and some children. If a child needs to take treatment for edema or high blood pressure, their doctor will recommend if hydrochlorothiazide is right for them.

For some of its uses, hydrochlorothiazide may be taken together with other medications.

It’s still not completely understood how hydrochlorothiazide works over time for blood pressure treatment. The drug causes your body to get rid of more sodium and chloride than usual. (Sodium and chloride are certain electrolytes in your body.) By doing this, the drug also causes your body to get rid of more water than usual.

This is how hydrochlorothiazide works as a diuretic and reduces edema (water retention).

But it’s also thought that helping your body get rid of salt and water may be how hydrochlorothiazide works for hypertension. It’s still not completely understood how this helps lower blood pressure over a long-term period.

Some important things to consider and discuss with your doctor about using hydrochlorothiazide include:

  • your overall health
  • any medical conditions you may have

You’ll also want to consider other medications you may be taking. These and other things to think about and discuss with your doctor are described below.

Interactions

Taking medications, vaccines, foods, and other things with a certain drug can affect how the drug works. These effects are called interactions.

Before taking hydrochlorothiazide oral tablets, be sure to tell your doctor about all medications you take, including prescription and over-the-counter types. Also describe any vitamins, herbs, or supplements you use. Your doctor or pharmacist can tell you about any interactions these items may cause with hydrochlorothiazide oral tablets.

Interactions with drugs or supplements

Hydrochlorothiazide oral tablets can interact with several types of drugs, including:

This list does not contain all types of drugs that may interact with hydrochlorothiazide oral tablets. Your doctor or pharmacist can tell you more about these interactions and any others that may occur with hydrochlorothiazide.

Other interactions

Hydrochlorothiazide may interact with lab tests that look at how well your parathyroid glands are working. (Your parathyroid glands are near your thyroid gland, and they make the parathyroid hormone.)

Be sure your doctor is aware that you’re taking hydrochlorothiazide if you need to have lab work for your parathyroid gland. Your doctor may have you temporarily stop taking this medication around the time of your lab work.

Warnings

Hydrochlorothiazide oral tablets may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take hydrochlorothiazide oral tablets. Factors to consider include those in the list below.

  • Anuria. With anuria, your kidneys stop making urine. This condition is usually caused by kidney disease, such as chronic kidney disease. Having anuria is a contraindication for hydrochlorothiazide, which means people with this condition should not use the drug. If you have anuria, talk with your doctor about safer options to treat your condition.
  • Kidney disease. When used in people with kidney disease, hydrochlorothiazide may cause azotemia (kidney injury or damage). Hydrochlorothiazide should be used cautiously in people with kidney disease, especially if their kidney condition is severe. Your doctor can help determine whether hydrochlorothiazide is safe for you if you have a kidney condition.
  • Liver problems. When used in people with liver problems, hydrochlorothiazide may increase their risk for electrolyte problems. If you have a liver problem, your doctor can help determine if hydrochlorothiazide is safe for you to take.
  • Allergic reaction. If you’ve had an allergic reaction to hydrochlorothiazide oral tablets or any of their ingredients, you should not take the tablets. Ask your doctor what other medications are better options for you.
  • Sulfa allergy. Hydrochlorothiazide is a sulfonamide, which is also sometimes called a “sulfa” drug. Sulfa drugs can cause a sulfa allergic reaction in some people. You should not take hydrochlorothiazide if you have a sulfa allergy. In fact, this is a contraindication for hydrochlorothiazide, which means the drug should not be used in people with this condition.

Use with alcohol

In general, it’s best to avoid or minimize alcohol consumption while you’re taking hydrochlorothiazide.

This is because alcohol can interact with hydrochlorothiazide and cause your blood pressure to go too low. This can increase your risk for side effects, such as low blood pressure, dizziness, and orthostatic hypotension. (To learn more about these side effects, see the “What are hydrochlorothiazide oral tablet’s side effects?” section above.)

Your doctor can help determine how much alcohol, if any, is safe for you to drink while you’re taking hydrochlorothiazide.

Pregnancy and breastfeeding

This drug may not be safe to take while pregnant. If you’re pregnant or planning to become pregnant, talk with your doctor before you use hydrochlorothiazide.

You should not breastfeed while you’re using hydrochlorothiazide. This is because the drug passes into breast milk. And it could cause serious side effects in a child who’s breastfed. Talk with your doctor about safe ways to feed your child if you’re taking hydrochlorothiazide.

Find answers to some commonly asked questions about hydrochlorothiazide oral tablets.

How does hydrochlorothiazide work? And how long does it stay in your system?

It’s still not completely understood how hydrochlorothiazide works for treating high blood pressure.

The drug causes your body to get rid of more sodium and chloride than usual. (Sodium and chloride are certain electrolytes in your body.) By doing this, the drug also causes your body to get rid of more water than normal.

This is how hydrochlorothiazide works as a diuretic and reduces edema (water retention).

But it’s also thought that helping your body get rid of salt and water may be how hydrochlorothiazide works for high blood pressure. It’s still not completely understood how this helps to lower blood pressure over a long-term period.

Hydrochlorothiazide stays in your system for a few days. Once you stop taking the drug, it should be fully cleared from your body after 3 or 4 days, at most.

If you have more questions about how hydrochlorothiazide works or affects your body, talk with your doctor or pharmacist.

Is hydrochlorothiazide a water pill? Does it cause weight loss?

Yes, hydrochlorothiazide is called a water pill. It is also known as a diuretic. Water pills help to lower blood pressure by working with your body to get rid of extra water and salt.

In studies of hydrochlorothiazide, people didn’t report weight loss as a side effect. But based on how the drug works, it’s possible you could lose some weight due to water loss while you’re taking the drug.

That said, hydrochlorothiazide isn’t prescribed for weight loss. And you should not take water pills to try to lose weight because these drugs are not approved for that use. Keep in mind that weight loss from losing water weight isn’t permanent.

If you have questions about your body weight and taking hydrochlorothiazide, talk with your doctor or pharmacist. They can suggest ways to help you maintain a body weight that’s healthy for you.

Does hydrochlorothiazide treat COVID-19?

No, hydrochlorothiazide doesn’t treat COVID-19. The drug isn’t approved for this use, and isn’t prescribed off-label for this condition, either. (With off-label use, a drug that’s approved to treat a certain condition is used to treat another condition.)

A drug with a similar name, called hydroxychloroquine, was looked at as a treatment option for COVID-19. But that drug also isn’t approved as a treatment option for this condition.

For the latest information on COVID-19, including care options, check out the Healthline hub.

What should I know about hydrochlorothiazide vs. chlorthalidone?

Hydrochlorothiazide and chlorthalidone have a lot in common. But these drugs also have some differences.

Both medications are prescribed to treat high blood pressure as well as edema (water retention).

Additionally, hydrochlorothiazide and chlorthalidone are also both classified as diuretics. Specifically, they’re both called thiazide diuretics. They cause your body to get rid of extra sodium and chloride, and also get rid of water.

Hydrochlorothiazide and chlorthalidone can interact with many of the same medications. These include:

And, the drugs can cause many of the same side effects, including:

Unlike hydrochlorothiazide, chlorthalidone is rarely taken more than once a day.

If you have more questions about how hydrochlorothiazide compares with chlorthalidone, talk with your doctor or pharmacist. They can tell you more about these medications and recommend which one is better for your condition.

Can you abruptly stop taking hydrochlorothiazide?

Talk with your doctor or pharmacist before you stop taking hydrochlorothiazide or any other medication you’ve been prescribed.

Hydrochlorothiazide doesn’t cause dependency and isn’t known to cause withdrawal symptoms. (With dependency, your body needs a drug in order for you to feel normal. Sometimes, stopping a drug that causes dependency can lead to withdrawal symptoms.)

But suddenly stopping hydrochlorothiazide may cause a “rebound” effect. With this effect from hydrochlorothiazide, your blood pressure increases or your body retains more water than usual.

A rebound effect doesn’t happen in everyone who takes hydrochlorothiazide. When it does occur, it tends to go away on its own after a few days. But increases in blood pressure or retention of water can be dangerous for some people.

For this reason, you should not stop taking hydrochlorothiazide unless your doctor specifically says it’s OK to do so. Always talk with your doctor or pharmacist if you’re thinking about stopping a medication, including hydrochlorothiazide.

How much water should you drink while you’re taking hydrochlorothiazide?

It depends. Staying hydrated while you’re taking a diuretic such as hydrochlorothiazide can be tricky.

You should talk with your doctor about this and ask how much water you should drink while you’re taking hydrochlorothiazide.

In general, you can drink water as you would if you weren’t taking hydrochlorothiazide. But your doctor may have you restrict your fluid intake, depending on the condition you’re using hydrochlorothiazide to treat.

Also, because hydrochlorothiazide causes your body to get rid of fluid, it can cause dehydration as a side effect. (With dehydration, you have a low level of fluid in your body.) So it’s important that you stay hydrated while you’re taking the medication.

Talk with your doctor or pharmacist about how much water you should drink each day while you’re taking hydrochlorothiazide. They can advise you based on your medical history and current health.

Do not take more hydrochlorothiazide oral tablets than your doctor prescribes. Using more than this can lead to serious side effects.

Symptoms of overdose

Symptoms caused by an overdose can include:

What to do in case you take too much hydrochlorothiazide oral tablet

Call your doctor if you think you’ve taken too much hydrochlorothiazide. You can also call 800-222-1222 to reach the American Association of Poison Control Centers, or use their online resource. However, if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.

Costs of prescription drugs can vary depending on many factors. These factors include what your insurance plan covers and which pharmacy you use. To find current prices for hydrochlorothiazide oral tablets in your area, visit GoodRx.com.

Financial assistance to help you pay for hydrochlorothiazide oral tablets may be available. Medicine Assistance Tool and NeedyMeds are two websites that provide resources to help reduce the cost of hydrochlorothiazide oral tablets.

These websites also offer tools to help you find low-cost healthcare and certain educational resources. To learn more, visit their websites.

Talk with your doctor if you’d like to know more about using hydrochlorothiazide for high blood pressure or edema (water retention).

You may want to ask your doctor about other treatments for these conditions. Here are a few articles about treatments that you may find helpful:

Additionally, you can sign up for Healthline’s heart health newsletter to learn more about your condition and ways to manage it.

Also, here are a few questions you may ask your doctor about hydrochlorothiazide oral tablets:

  • How will I know if hydrochlorothiazide is working to treat my condition?
  • Should I use other treatments for my condition while I’m taking hydrochlorothiazide?
  • Can I take hydrochlorothiazide oral tablets with acetaminophen (Tylenol)?

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.