Hydrochlorothiazide (HCTZ)

Order generic Microzide for hypertension

Hydrochlorothiazide is a high blood pressure treatment. It can reduce blood pressure to normal levels, with or without additional medication, which helps prevent strokes and heart disease.

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Reviewed by Roy Kedem, MD

Information last reviewed 10/22/20


What is Hydrochlorothiazide?

Hydrochlorothiazide tablets (also known as HCTZ or Microzide) are used to treat high blood pressure. An estimated 108 million adults in the US have high blood pressure. In 2018, nearly half a million adults in the US died from conditions related to high blood pressure, so it’s really important to get your blood pressure under control. Treating high blood pressure can help prevent heart attacks and strokes.

Hydrochlorothiazide: what does it do?

Hydrochlorothiazide is a type of high blood pressure medication (antihypertensive) that can reduce your blood pressure to healthier levels. You may not notice any symptoms, but high blood pressure puts strain on your blood vessels, which increases your risk of dangerous diseases such as heart disease and cerebrovascular disease, which can cause strokes. 

How Hydrochlorothiazide works

Hydrochlorothiazide is a diuretic, which works on the kidney to prevent reabsorption of sodium. This leads to excretion of sodium into the urine, which in turn draws water out as well.  The increased urine output leads to lower blood volume, which then leads to lower blood pressure.

What is Hydrochlorothiazide used for?

Hydrochlorothiazide is a medication used either alone or as an additional therapy to treat high blood pressure. Left untreated, high blood pressure can cause damage to various structures in the body such as the brain, heart, blood vessels and kidneys. This can result in dangerous conditions such as heart attacks and strokes.

How quickly does Hydrochlorothiazide start working?

Hydrochlorothiazide should start to work within 2 hours of taking the first dose. However, it can take several weeks to have an optimal effect on blood pressure.

When does Hydrochlorothiazide peak?

After taking Hydrochlorothiazide, the first pharmacological effects occur in approximately 2 hours.  The medication reaches its peak in approximately 4 hours. Each dose will last 6 to 12 hours. 

What are HCTZ tablets?

HCTZ tablets are also known as Hydrochlorothiazide tablets. HCTZ is simply an abbreviation of Hydrochlorothiazide. HCTZ tablets are antihypertensives. That means that they help to reduce your blood pressure to safe levels. 

HCTZ uses

HCTZ tablets are primarily used to reduce high blood pressure, however, they can also be used to reduce edema - a type of swelling or water retention - associated with certain medical conditions. 

What drug class is HCTZ?

HCTZ is a diuretic medication used for the treatment of high blood pressure. There are three different types of diuretics based on what part of the kidney they affect. More specifically, HCTZ is a thiazide diuretic. Diuretics are designed to increase the amount of salt and water excreted from the body into the urine. As more water is excreted from the body, blood volume decreases and so will blood pressure. 


Active ingredient

The active ingredient in Hydrochlorothiazide is hydrochlorothiazide. This produces diuretic effects and is used to reduce blood pressure.

Inactive ingredients

Inactive ingredients can vary between different manufacturers. For Hydrochlorothiazide sold under the brand name Microzide, the inactive ingredients are colloidal silicon dioxide, corn starch, lactose monohydrate, magnesium stearate. Gelatin capsules contain D&C Red No. 28, D&C Yellow No. 10, FD&C Blue No. 1, gelatin, titanium dioxide. The capsules are printed with edible ink containing black iron oxide, D&C Yellow No. 10, FD&C Blue No. 1, FD&C Blue No. 2, FD&C Red No. 40. 

Which ingredients can cause an allergic reaction?

Hydrochlorothiazide medication can cause a severe allergic reaction which presents as hives, swelling of the lips or face, chest tightness, itchy throat and dizziness. If you experience this please get emergency medical attention right away. If you have previously had an allergic reaction to sulphonamide-containing medications, please let your doctor know and refrain from taking the medication again. 


Hydrochlorothiazide dosage

Hydrochlorothiazide is available as 12.5mg, 25mg and 50mg tablets. However, doses above 25mg are rarely prescribed as they can place you at risk of low sodium and low potassium and do not confer additional benefit.

When to take Hydrochlorothiazide

It is recommended that the medication is taken before 6pm as it can increase the need to urinate during the night. 

What to do when Hydrochlorothiazide doesn't work for you

When you start Hydrochlorothiazide to control your blood pressure, your doctor will most likely require you to keep a blood pressure log at home during the first few weeks of treatment. If your blood pressure remains high despite compliance with Hydrochlorothiazide, it is imperative that you make another appointment with your doctor to discuss a change in dosage or medication. 

Hydrochlorothiazide: can I stop taking it?

Your blood pressure may have reduced to normal levels, but if you stop taking Hydrochlorothiazide, your blood pressure may increase again. Therefore, you should continue taking Hydrochlorothiazide until advised otherwise by your doctor. If you are finding it difficult to tolerate the side effects of Hydrochlorothiazide, you can discuss this with your doctor, who may be able to suggest some alternative treatments. 

Lifestyle changes such as regular exercise and eating a low sodium diet can help to reduce your blood pressure. If you take these steps, you may find that you can maintain your blood pressure at healthy levels without needing medication. 

Should I take Hydrochlorothiazide with or without food?

Hydrochlorothiazide can be taken with or without food. Taking Hydrochlorothiazide with food may help to alleviate some of the side effects. 

Side Effects

Hydrochlorothiazide side effects

What are the most common side effects of Hydrochlorothiazide?

  • Dizziness
  • Headache
  • Tingling feelings in your hands, legs and feet
  • Weakness
  • Nausea
  • Poor appetite
  • Diarrhea
  • Constipation
  • Dry mouth / increased thirst
  • Erectile dysfunction (in men)

Rare side effects of Hydrochlorothiazide

Some rare but serious side effects can also occur from taking Hydrochlorothiazide:

  • Severe skin reaction (Stevens-Johnson syndrome)
  • Kidney failure
  • Blurred vision

For a full list of side effects, please see the patient information leaflet provided with your medication.

Hydrochlorothiazide drug interactions

Hydrochlorothiazide can interact with a number of medications, including:

  • Lithium 
  • Digoxin 
  • Muscle relaxants 
  • Anesthetics
  • Pain killers
  • Medications for diabetes
  • Antihypertensives 
  • Corticosteroids
  • Diuretics
  • Chemotherapy agents
  • Warfarin

Therefore, for your own safety, it is essential that you let your doctor know if you are taking any other medications. 


Hydrochlorothiazide should not be used by anyone who is allergic to Hydrochlorothiazide or other sulfonamide-derived medications such as Sulfamethoxazole. Hydrochlorothiazide should be used with caution in people with the following conditions:

  • Kidney disease
  • Liver disease
  • Bronchial asthma 
  • Systemic lupus erythematosus.

Why is Hydrochlorothiazide contraindicated in diabetes?

Diabetes is a common contraindication for Hydrochlorothiazide. The prolonged use of thiazide diuretics like Hydrochlorothiazide may cause diabetes by causing glucose intolerance. It is also possible that Hydrochlorothiazide results in the increased production of glucose from the liver, another factor that might lead to diabetes. 

Can you take Hydrochlorothiazide when you're pregnant?

Studies in mice and rats have not found Hydrochlorothiazide to cause any damage to the fetus. However, for ethical reasons, no reliable human studies have been undertaken to examine the effects of Hydrochlorothiazide in pregnancy. Therefore, it is recommended that Hydrochlorothiazide is avoided during pregnancy unless the benefits of treatment would outweigh the risks.

Hydrochlorothiazide, can you drink alcohol while taking it?

Patients commonly ask if they can drink alcohol when taking Hydrochlorothiazide.  A reduction in alcohol intake while taking Hydrochlorothiazide is recommended, as alcohol itself can lower blood pressure. Coupled with alcohol, Hydrochlorothiazide can cause blood pressure to drop too low, which may make you feel dizzy or faint. 

Will Hydrochlorothiazide lower blood pressure?

Hydrochlorothiazide is most commonly prescribed to reduce blood pressure, although it can be prescribed for other purposes. It is effective in lowering blood pressure in people with hypertension (high blood pressure).

HCTZ and breastfeeding

Hydrochlorothiazide can pass into breast milk. Therefore a decision may need to be made about whether to discontinue breastfeeding and to continue taking Hydrochlorothiazide or to stop taking Hydrochlorothiazide and to continue breastfeeding. Your doctor should be able to help you weigh the pros and cons before making this decision. 

Will Hydrochlorothiazide lower heart rate?

A study looking into the effects of blood pressure medication on heart rate found that Hydrochlorothiazide can lower the heart rate over time. 

Can Hydrochlorothiazide cause gout?

A common side effect of thiazide diuretics like Hydrochlorothiazide is hyperuricemia. Hyperuricemia is a term used to describe an increase in uric acid levels in the blood. Increased uric acid levels can lead to gout. Diuretics, such as Hydrochlorothiazide, reduce the rate of urate excretion and increase urate reabsorption in the kidneys, thus leading to hyperuricemia and gout.

Can Hydrochlorothiazide cause hair loss?

A known side effect of Hydrochlorothiazide is hair loss and hair thinning. This side effect can be temporary or permanent. 

Can Hydrochlorothiazide cause weight gain?

A study conducted comparing weight gain properties of different medications concluded that Hydrochlorothiazide and other diuretics do not cause weight gain and can actually cause weight loss.

Can Hydrochlorothiazide cause weight loss?

The above study concluded that Hydrochlorothiazide and other diuretics can result in moderate weight loss of about 0.4-2.7kg. However, people experience different side effects when taking Hydrochlorothiazide, so weight loss might not be seen in everyone taking the medication.

Can Hydrochlorothiazide cause depression?

A nationwide Dutch study conducted between 2005 and 2015 found that there is no link between diuretics and an increased risk of depression. The study identified nine blood pressure medications that actually lowered the risk of depression, but Hydrochlorothiazide was not one of these drugs. None of the 41 drugs studied caused an increased risk of depression.

Can Hydrochlorothiazide cause leg cramps?

Like other diuretics, Hydrochlorothiazide can cause leg cramps. This occurs as diuretics deplete sodium and fluid levels in the body. They also cause a loss of potassium, calcium and magnesium, leading to cramps.

Treatment Options

Hydrochlorothiazide alternatives

There is a wide range of different treatments available for high blood pressure. Hydrochlorothiazide is a type of high blood pressure medication known as a diuretic. Other diuretics include Furosemide, Indapamide and Metolazone. Aside from diuretics, there are various different classes of medication that can treat high blood pressure, such as ACE-inhibitors, beta-blockers, angiotensin II receptor blockers, calcium channel blockers and others. The table below outlines the different high blood pressure medications available through Medzino and what type of medication they are:

Lifestyle changes to reduce blood pressure

Various lifestyle changes can help to lower your blood pressure. Most involve taking steps to improve your overall health, such as maintaining a healthy diet and getting regular exercise. It may also help to lose weight if you are overweight and to reduce levels of salt, alcohol, and caffeine in your diet. Stress reduction can also help to reduce your blood pressure. Yoga and mindfulness can help to reduce stress levels, but you may just need to make sure you find time to relax. 

Which is better: Hydrochlorothiazide or Chlorthalidone?

Chlorthalidone is found to produce more significant reductions in blood pressure compared to Hydrochlorothiazide in this 2015 study. However, Chlorthalidone is also associated with a greater decline in potassium levels in the blood.

Hydrochlorothiazide or Furosemide?

In the long term treatment of high blood pressure, a study found that Hydrochlorothiazide has a better anti-hypertensive effect (better at lowering blood pressure) than Furosemide. This may be due to Hydrochlorothiazide having a more prolonged diuretic effect than Furosemide.  

Which is better: Hydrochlorothiazide or Lasix?

Lasix is just a brand name for Furosemide. The above study found that Hydrochlorothiazide is better at lowering blood pressure in patients compared to Furosemide. 

Hydrochlorothiazide or Lisinopril?

While both Hydrochlorothiazide and Lisinopril reduce blood pressure in patients, a study found that lisinopril has a more statistically significant effect in lowering blood pressure compared to Hydrochlorothiazide.  

Hydrochlorothiazide or Spironolactone?

A prospective study found that Spironolactone (a potassium-sparing diuretic) is more effective at lowering systolic and diastolic blood pressure compared to Hydrochlorothiazide (a thiazide diuretic). 

Hydrochlorothiazide or Amlodipine?

Amlodipine and Hydrochlorothiazide are both used to treat high blood pressure. They can be used alone or in combination. A study found that Amlodipine was more effective in lowering blood pressure in patients older than 60 compared to Hydrochlorothiazide. 

Hydrochlorothiazide or Losartan?

Losartan and Hydrochlorothiazide are usually used in combination to treat high blood pressure. Losartan lowers blood pressure by relaxing the blood vessels and increasing the blood and oxygen supply to the heart. Hydrochlorothiazide works by lowering blood pressure by increasing the volume of water excreted in the urine. A combination of both drugs lowers blood pressure better than each medication alone. No study has been conducted comparing the efficacy of each drug alone.  

Which drugs contain Hydrochlorothiazide?

Hydrochlorothiazide is the active ingredient in several branded drugs, including: 

  • Apo-Hydro 
  • Aquazide
  • BPZide 
  • Dichlotride 
  • Esidrex
  • Hydrochlorot
  • Hydrodiuril
  • HydroSaluric 
  • Hypothiazid
  • Microzide
  • Oretic

Several medications contain Hydrochlorothiazide in combination with other active ingredients such as:

  • Enalapril and Hydrochlorothiazide - Innozide
  • Irbesartan and Hydrochlorothiazide - Avalide
  • Lisinopril and Hydrochlorothiazide - Prinzide, Zestoretic
  • Losartan and Hydrochlorothiazide - Hyzaar
  • Olmesartan and Hydrochlorothiazide - Benicar
  • Quinapril and Hydrochlorothiazide - Accuretic 
  • Telmisartan and Hydrochlorothiazide - Micardis HCT 
  • Valsartan and Hydrochlorothiazide - Diovan HCT
  • Olmesartan, Amlodipine and Hydrochlorothiazide - Tribenzor


Disclaimer: This is not medical advice. You and your physician will determine if and how you should take any medication prescribed to you following a medical consultation.

  1. Mayo Clinic > 10 Ways to Control High Blood Pressure
  2. British Journal of Pharmacology > The abuse of diuretics as performance-enhancing drugs and masking agents in sport doping: pharmacology, toxicology and analysis
  3. Healthline > A list of high blood pressure medications
  4. CDC > Facts about hypertension
  5. FDA > Hydrochlorothiazide tablets
  6. StatPearls > Hydrochlorothiazide
  7. Mayo Clinic > Lisinopril and Hydrochlorothiazide
  8. Drugs.com > Olmesartan
  9. Mayo Clinic > Irbesartan and Hydrochlorothiazide
  10. UptoDate > Diuretics-induced hyperuricemia and gout
  11. AHA Journal > Antihypertensive drugs and risk of depression
  12. Dovepress > Medications that cause weight gain and alternatives in Canada: a narrative review
  13. American Journal of Hypertension > Comparison of effects of antihypertensive drugs on heart rate: changes from baseline by baseline group and over time. Department of Veterans Affairs Cooperative Study Group on Antihypertensive Agents
  14. Clinical Drug Investigations > A Comparative Evaluation of Amlodipine and Hydrochlorothiazide as Monotherapy in the Treatment of Isolated Systolic Hypertension in the Elderly
  15. Medicine > Spironolactone is superior to Hydrochlorothiazide for blood pressure control and arterial stiffness improvement
  16. JAMA Network > Furosemide Compared With Hydrochlorothiazide Long-term Treatment of Hypertension
  17. European Journal of Clinical Pharmacology >  A comparison of the effect of lisinopril and Hydrochlorothiazide on electrolyte balance in essential hypertension
  18. American Family Physician > Chlorthalidone vs. Hydrochlorothiazide for Treatment of Hypertension

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