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Hydrochlorothiazide: 10 Answers inc. Uses, Side Effects, and Dosage

Answers to the most common questions from patients prescribed with hydrochlorothiazide

Hydrochlorothiazide is an oral diuretic medication that is sometimes referred to by its abbreviation, HCTZ. Diuretics are medications that increase the body’s production of urine. This type of medication has a wide variety of possible uses, but hydrochlorothiazide is typically used for treating high blood pressure and swelling due to fluid buildup. It may be combined with other medications or used as a single therapy. Hydrochlorothiazide is on the World Health Organization’s List of Essential Medicines; this means that it is a safe and effective medicine critical to health systems.

The content on this page is provided for informational purposes only. If you have any questions or concerns about your treatment, you should talk to your doctor, pharmacist, or healthcare professional. This is particularly important if you are taking multiple medications or have any existing medical conditions.

  1. What is hydrochlorothiazide used for?
  2. What are the side effects of hydrochlorothiazide?
  3. How does hydrochlorothiazide work?
  4. How long does it take for hydrochlorothiazide to work?
  5. How long does hydrochlorothiazide stay in your system?
  6. How do you taper off hydrochlorothiazide?
  7. When should you take hydrochlorothiazide?
  8. Does hydrochlorothiazide cause weight loss?
  9. What dosage of hydrochlorothiazide should I take?
  10. What are the drug interactions with hydrochlorothiazide?

1. What is hydrochlorothiazide used for?

Since hydrochlorothiazide is a diuretic, it has a wide number of possible uses. However, it is most used to treat hypertension. Some studies suggestIn 2019 it was found that hydrochlorothiazide is somewhat less effective at blood pressure reduction than chlorthalidone, another diuretic, but comes with fewer negative side effects. Aside from hypertension, it can be used to treat symptomatic edema, diabetes insipidus, renal tubular acidosis, and kidney stones. In some cases, hydrochlorothiazide can also be used to prevent osteopenia and to treat hypoparathyroidism.

2. What are the side effects of hydrochlorothiazide?

Hydrochlorothiazide is known to have less adverse side effects than other diuretics. However, it is still possible to experience effects ranging from mild to severe when taking the drug. Mild side effects may subside after taking the medication for a few days or weeks, but if they persist or worsen you should speak with your doctor.

Mild Side Effects:

At high doses, some blood pressure medications like hydrochlorothiazide can also cause erectile dysfunction.

Serious Side Effects:

  • Blurred vision or eye pain
  • Potentially fatal skin reactions like Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN)
  • Kidney failure – symptoms such as weakness, shortness of breath, tiredness, confusion, less urine than usual
  • Irregular heartbeat
  • High blood sugar
  • Low potassium, magnesium, or sodium

If you experience any of these serious side effects, you should speak with your doctor or seek immediate medical attention if it is an emergency.

In some rare cases, patients can experience allergic reactions. Seek emergency medical care if you experience any of the following symptoms after taking hydrochlorothiazide.

  • Skin rash
  • Wheezing
  • Tightness in the throat or chest
  • Difficulty talking or breathing
  • Swelling of the face, lips, tongue, or throat

3. How does hydrochlorothiazide work?

As hydrochlorothiazide is a diuretic its main function is to increase urine production. It is not known exactly how it works in treating the conditions it is prescribed for. However, it is thought to work in the kidneys to help the body get rid of excess salt and water. Loss of fluid volume in the plasma, a part of blood, lowers blood pressure and prevents the heart from having to work as hard to pump blood throughout the body.

4. How long does it take for hydrochlorothiazide to work?

It is common for those who are prescribed hydrochlorothiazide to wonder how long it will take for the medication to take effect. Fortunately, the effects of the drug are relatively quick. After an oral dose, the effects typically begin in about two hours, peak in about four hours, and last for up to twelve hours before subsiding. The long-term effects of the drug on blood pressure are still not completely understood. Taking hydrochlorothiazide as prescribed is important in order to keep blood pressure at safe levels.

5. How long does hydrochlorothiazide stay in your system?

The length that hydrochlorothiazide can remain in the system varies widely. But regardless, it will remain in your system for a while after the effects of the drug have subsided. Typically, hydrochlorothiazide will have left the body entirely sometime between thirty and seventy-five hours after use.

6. How do you taper off hydrochlorothiazide?

Stopping the use of hydrochlorothiazide suddenly can be dangerous and may lead to a spike in blood pressure. That is why it is important to understand the best ways to taper off. Unfortunately, there is no ‘one size fits all’ approach to tapering off. The best way to stop taking the drug is to speak with your doctor about tapering your dose and follow their recommendations.

7. When should you take hydrochlorothiazide?

Generally, the recommended practice for taking hydrochlorothiazide is to take your daily dose after breakfast in the morning. If you are prescribed more than one dose it is best to take the last dose no later than six in the evening. You should your doses in a way that will affect your daily activities and sleep as little as possible. Taking a diuretic close to bedtime can result in nighttime awakenings to urinate. If you need help planning your doses, speak with your doctor.

8. Does hydrochlorothiazide cause weight loss?

While hydrochlorothiazide is not prescribed for weight loss, it may lead to weight loss in some patients. Some studies have reported that up to 50% of responders lost at least 1kg of weight while taking hydrochlorothiazide. The number of patients who report weight loss increases for those prescribed with higher doses.

9. What dosage of hydrochlorothiazide should I take?

The proper dose of the drug will be unique to each patient. Always follow your doctor’s orders or the directions on the label. The following information presents common doses of the drug. This information is for your information only. Your doctor will tell you the dose you should follow.

The average doses prescribed of hydrochlorothiazide are based on the age and weight of the patient as well as the condition it is being used to treat.

For hypertension:

  • Adults - 12.5mg daily, increasing gradually up to 50mg daily
  • Children - Dose is based on weight and will be determined by your doctor

For fluid retention:

  • Adults – 25 to 100mg daily
  • Children – Dose is based on weight and will be determined by your doctor

Regardless of the condition you are treating, if you miss a dose you should take it as soon as possible unless it is almost time for your next dose. If it is time for your next dose skip the missed dose and continue with your regular schedule. You should never double doses.

10. What are the drug interactions with hydrochlorothiazide?

Hydrochlorothiazide has potential interactions with several drugs. Different drugs may cause different interactions such as reduced effectiveness or increased side effects. Below is a list of some common interactions. This is not a complete list and you should speak with your doctor about any medication you are planning to take alongside hydrochlorothiazide.

  • Barbiturates – These drugs may lower blood pressure too much and lead to dizziness or fainting.
  • Lithium – Hydrochlorothiazide slows the release of lithium from the body, so taking it may lead to high lithium levels or lithium toxicity.
  • Cholesterol-lowering drugs – Taking certain cholesterol-lowering drugs may cause an interaction that reduces the effectiveness of hydrochlorothiazide. Your doctor should prescribe cholesterol-lowering medications that don’t interact with hydrochlorothiazide if you need them.
  • Corticosteroids – Taking corticosteroids may lead to dangerously low levels of already depleted electrolytes (like potassium) due to increased urination.

It is not uncommon for a doctor to prescribe hydrochlorothiazide along with other blood pressure-lowering medications. If this happens, be careful when moving from a lying down position to a sitting position, or from sitting to standing. The movements can cause dizziness if your blood pressure is low.


The content on this page is provided for informational purposes only. If you have any questions or concerns about your treatment, you should talk to your doctor, pharmacist, or healthcare professional. This is particularly important if you are taking multiple medications or have any existing medical conditions.

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