Hydrochlorothiazide dosage, forms, and strengths

Hydrochlorothiazide is a generic prescription diuretic (“water pill”), meaning it increases the amount of urine a person produces, and is from a class of drugs called thiazide diuretics. Diuretics are commonly used to treat high blood pressure and swelling due to water retention (edema). Doctors may use it as a standalone therapy but more often prescribe it with other drugs. It’s so commonly used that many drugs on the market combine hydrochlorothiazide with another blood pressure medication, such as a medication that dilates or relaxes blood vessels. Hydrochlorothiazide doses will vary, but people can expect to take one or two pills daily. 

Hydrochlorothiazide forms and strengths

Hydrochlorothiazide is taken orally in one of two dosage forms:

• Tablet: 12.5 mg, 25 mg, 50 mg

• Capsule: 12.5 mg

Hydrochlorothiazide dosage for adults

The U.S. Food and Drug Administration (FDA) has approved hydrochlorothiazide to treat chronic or long-term hypertension (high blood pressure) or edema (fluid buildup). For both conditions, it can be used as a standalone treatment or in combination with other drugs. Dosages will be individualized based on the severity of the condition and other drugs being used. The only people who cannot safely take hydrochlorothiazide are people who have stopped urinating (anuria) or who are allergic to sulfonamide or “sulfa” drugs.

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Hydrochlorothiazide dosage for hypertension

Hydrochlorothiazide has been a major treatment for blood pressure since the 1960s. Doctors can prescribe it alone but will most likely use it with other blood pressure drugs such as ACE inhibitors, angiotensin II receptor blockers, beta blockers, and calcium channel blockers. Many blood pressure drugs combine hydrochlorothiazide with another blood pressure drug. These products are usually recognizable by the initials “HCT” or “HCTZ” added to the end of the drug, such as the brand-name Exforge HCT (amlodipine-valsartan-HCTZ).

Hydrochlorothiazide reduces the body's water by increasing the amount of sodium in the urine excreted through the kidneys. The extra sodium in the urine pulls along extra water and potassium into the urine as well, causing larger volumes of urine to be excreted. With less water in the body, blood volume goes down, lowering blood pressure. Dosages will vary depending on how bad the blood pressure problem is and how well other drugs are working. The starting dose may be small (12.5 mg) but no larger than 25 mg. The dose may increase to a maximum dosage of 50 mg daily in two to four weeks.

• Standard adult dosage for hypertension: 25–50 mg daily taken as a single or divided dose

• Maximum adult dosage for hypertension: 50 mg daily

Hydrochlorothiazide dosage for edema

Edema is tissue swelling caused by fluid retention. It has various causes, including congestive heart failure, kidney disease, liver dysfunction, blood vessel problems, lymphatic system problems, pregnancy, infection, diet, and medication side effects such as corticosteroid or estrogen therapy. Doctors will usually treat the underlying cause but may add a diuretic to reduce fluid buildup and swelling. 

Hydrochlorothiazide and other thiazide diuretics have been a first-line treatment for edema for many decades. However, hydrochlorothiazide can deplete the body of potassium, a potentially serious side effect. For this reason, it’s often prescribed with or combined with potassium-sparing diuretics such as spironolactone, triamterene, or amiloride.

Doses will vary based on the underlying condition and other drugs being taken. While the starting dose is low, the recommended dose can be as high as 100 mg per day. Larger doses require people to split them into two separate doses.

• Standard adult dosage for edema: 25–100 mg daily taken as a single or divided dose

• Maximum adult dosage for edema: 200 mg daily

Hydrochlorothiazide dosage for children

Hydrochlorothiazide is FDA-approved to treat high blood pressure in infants and children or to provide increased urine excretion in those who are retaining water. As in adults, it can be prescribed alone or in combination with other diuretics or high blood pressure medications.

Hydrochlorothiazide dosage restrictions

Hydrochlorothiazide does not require dosage modifications in people with mild to moderate kidney disease, liver disease, or other medical conditions. However, it is not appropriate for use in people with severe kidney diseaseor who are on dialysis. The FDA warns that hydrochlorothiazide should be used with caution in people with severe liver cirrhosis but has not specified any dosage changes. 

Hydrochlorothiazide dosage for pets

Although hydrochlorothiazide isn’t a veterinarian’s first choice as a diuretic, it is still used as an add-on or backup treatment in dogs and cats to treat hypertension, congestive heart failure, fluid buildup in the abdomen (ascites), calcium oxalate kidney stones, and a very rare kidney disease called nephrogenic diabetes insipidus. Dosages will vary based on the condition being treated. They will range from as little as 1 mg per kilogram (0.5 mg/lb) of body weight to as much as 4 mg/kg (1.8 mg/lb). As in humans, the most common problems caused by hydrochlorothiazide in pets are low potassium and dehydration, so pet parents should be familiar with the symptoms of these problems and contact the veterinarian if they occur.

How to take hydrochlorothiazide

Hydrochlorothiazide is taken daily as a tablet or capsule. Some people will take the entire dose once per day, but others may have to divide the daily dose into two separate doses:

• Take your medicine as directed. Your dose may need to be changed several times to find what works best.

• Try to take the daily dose in the morning, or morning and early/mid-afternoon with two doses, so its diuretic effects don’t interfere with sleeping.

• Swallow the tablet or capsule whole.

• If the tablet can’t be swallowed, it can be crushed, mixed with a small amount of liquid, and taken that way.

• Store hydrochlorothiazide tablets in a closed container at room temperature. 

• Store hydrochlorothiazide capsules in a closed container at room temperature, protected from light and moisture. Do not freeze.

Hydrochlorothiazide dosage FAQs

How long does it take hydrochlorothiazide to work?

The effects of hydrochlorothiazide begin about two hours after a dose is taken in adults, and may take a bit longer in kids. The drug reaches its peak effects in adults after about four hours.

How long does hydrochlorothiazide stay in your system?

The body eliminates half a dose of hydrochlorothiazide in six to 15 hours. After about 24 hours, almost 2/3 of the dose has been urinated out of the body. The clinical effects of hydrochlorothiazide last for six to 12 hours after a dose is taken.

What happens if I miss a dose of hydrochlorothiazide?

Take a missed dose as soon as it’s remembered. However, skip the missed dose if it’s almost time for the next dose. Just take that next dose on time. Never take a double dose to make up for a missed dose.

How long can you take hydrochlorothiazide?

Hydrochlorothiazide is often prescribed as a long-term treatment. Some people will take it for years or even a lifetime. It is not known to cause adverse effects due to long-term use. However, people will need to be monitored for low potassium, other electrolyte imbalances, and other issues as long as they take hydrochlorothiazide.

How do I stop taking hydrochlorothiazide?

Hydrochlorothiazide can be stopped at any time without causing withdrawal. Before stopping this drug, however, get medical advice from a healthcare professional.

A doctor may have good causes to stop this drug, including allergic reactions, severe kidney problems, low potassium, blurred vision (myopia), or angle-closure glaucoma. In many cases, the doctor will switch to another blood pressure medication or diuretic. The doctor may add a potassium-sparing diuretic for low potassium that helps the body retain potassium. Loop diuretics such as furosemide and potassium-sparing diuretics are usually the alternatives of choice if thiazide diuretics can’t be taken. 

Can you overdose on hydrochlorothiazide?

An overdose of hydrochlorothiazide will dehydrate the body and deplete electrolytes. Both can be serious medical issues and require immediate medical help to reverse. Symptoms of a hydrochlorothiazide overdose include dry mouth, dry skin, dry eyes, frequent peeing, nausea, vomiting, sleepiness, dizziness, confusion, fainting, muscle cramping, heart rhythm irregularities, vision changes, seizures, and coma. 

What interacts with hydrochlorothiazide?

To avoid potential drug interactions, tell the prescribing healthcare provider about all the prescription drugs, over-the-counter medications, and supplements that you’re taking regularly, especially:

• Other diuretics

• Blood pressure drugs

• Nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin or ibuprofen

• Drugs that treat high blood sugar, including insulin

• Corticosteroids like prednisone

• Muscle relaxants

• The cholesterol drugs cholestyramine or colestipol

• Medicines that can cause orthostatic hypotension, like narcotic pain medications, barbiturates, or alcohol

• Drugs that tighten blood vessels, like epinephrine

• The bipolar treatment, lithium

• The heart medication digoxin

What happens when you mix hydrochlorothiazide and alcohol?

Avoid alcohol when taking hydrochlorothiazide. The combination can worsen orthostatic hypotension (getting very lightheaded when standing up), one of the side effects of hydrochlorothiazide. This occurs when blood pressure falls rapidly when standing up or changing position. People can feel temporarily faint, or they can black out or fall, causing injury.

Is it safe to take hydrochlorothiazide during pregnancy?

Women who are pregnant or considering pregnancy should get medical advice about the risks and benefits of taking hydrochlorothiazide. Animal studies have not shown any risk for birth defects, but the drug has not been studied in pregnant women. The drug does cross the placenta and is present in cord blood, so there is a theoretical possibility that it could cause adverse effects in a fetus. 

Is it safe to take hydrochlorothiazide while breastfeeding?

The American Academy of Pediatrics considers hydrochlorothiazide compatible with breastfeeding in doses of 50 mg daily or less. Hydrochlorothiazide does show up in breast milk, and at high enough doses it could theoretically cause problems in a nursing infant. At higher doses, thiazide diuretics also suppress lactation. 

What are the most common side effects of hydrochlorothiazide?

Because hydrochlorothiazide increases the excretion of water and electrolytes like sodium and postassium, the most common side effects are dehydration and electrolyte imbalances, such as low potassium levels (hypokalemia), low sodium levels (hyponatremia), low magnesium levels, high calcium levels, and low chloride levels. Thiazide diuretics can also cause low blood pressure (hypotension), increased uric acid levels in the blood (hyperuricemia), elevated blood sugar, and elevated cholesterol and fats. Other common side effects include constipation and abdominal pain.

Sources

• Hydrochlorothiazide, Drugs and Lactation Database

• Hydrochlorothiazide, StatPearls

• Hydrochlorothiazide capsule prescribing information, DailyMed (NIH National Library of Medicine)

• Hydrochlorothiazide drug summary, Prescriber’s Digital Reference (PDR)

• Hydrochlorothiazide tablet prescribing information, DailyMed (NIH National Library of Medicine)

• Plumb’s Veterinary Drug Manual, 7 edition

• The transfer of drugs and other chemicals into human milk, American Academy of Pediatrics (AAP)

• Thiazide overdose, Mount Sinai

• UpToDate Lexidrug, Wolters Kluwer