10 Hydrochlorothiazide (HCTZ) Side Effects You Should Know About

Hydrochlorothiazide (Microzide) is a diuretic, or water pill, that’s a first-choice medication for treating high blood pressure. It can also treat edema (fluid buildup) from various health conditions. It’s part of a medication class called thiazide diuretics. These medications help your kidneys remove extra fluid and salt from your body through your urine.

But hydrochlorothiazide (HCTZ) isn’t without its risks. As with any medication, it can be a delicate balancing act between hydrochlorothiazide side effects and benefits. Here’s what you should know.

Hydrochlorothiazide (HCTZ) side effects at a glance

Most people can take hydrochlorothiazide without serious issues. The most noticeable side effect is peeing more, which is to be expected. This is how the medication works to remove fluid and salt from the body.

But there are other potential hydrochlorothiazide side effects. These side effects are usually mild and improve after your body gets used to the medication. Often, they’re due to electrolyte imbalances caused by peeing more often.

Mild hydrochlorothiazide side effects include:

• Dizziness 

• Weakness

• Tiredness

• Headache

• Muscle cramps

• High blood glucose (sugar)

• Sensitivity to sunlight

• Sexual problems

• Gastrointestinal problems, including diarrhea or constipation

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While rare, more severe side effects can also occur with hydrochlorothiazide, including:

• Pancreatitis

• Severely low sodium, magnesium, or potassium levels

• Kidney problems

• Eye problems

Below, we take a closer look at 10 hydrochlorothiazide effects.

1. Electrolyte imbalances

Hydrochlorothiazide makes you pee more because it helps remove fluid from your body. But this can cause electrolytes to fall out of balance. Sodium, potassium, or magnesium levels in your blood can go down, and your calcium levels can go up. These electrolyte changes usually happen within the first few weeks of hydrochlorothiazide treatment.

Here are a few strategies for managing electrolyte imbalances:

• Regular monitoring: Your healthcare team may periodically run blood tests to check your electrolyte levels to help them identify issues early.

• Symptom recognition: Be alert for symptoms of electrolyte imbalances, such as muscle weakness or cramps, fatigue, and an irregular heartbeat. Report these to your healthcare team right away.

• Dietary adjustments: Your healthcare team may recommend dietary adjustments, such as eating more potassium-rich foods.

• Medication management: Your prescriber may adjust your dose, add another medication or supplement, or switch you to a different diuretic.

EXPERT PICKS: WHAT TO READ NEXT

• What’s a typical dose? Pharmacists review common hydrochlorothiazide dosages, plus what to do if you miss your dose.

• Tips for taking hydrochlorothiazide: Want to know the best time to take hydrochlorothiazide? Get answers to this and other common questions about taking this medication.

• What to avoid: Learn about potential hydrochlorothiazide interactions and how to manage them.

2. Dizziness

Hydrochlorothiazide is used to lower blood pressure. But sometimes it can make your blood pressure drop too low. This can make you feel lightheaded or dizzy, especially when you stand up too fast or shift positions.

It’s normal to have mild dizziness after starting hydrochlorothiazide. This should improve as your body gets used to the medication. But here are a few tips for managing it in the meantime:

• Rise slowly when you’re moving from a seated or lying-down position to standing.

• Drink enough fluids throughout the day to avoid dehydration.

• Avoid driving or performing other activities that can be dangerous if you’re dizzy.

• Monitor your blood pressure at home, and tell your prescriber if it’s dropping too low.

• Avoid alcohol, since it can worsen dizziness.

If you have dizziness that doesn’t improve, reach out to your healthcare team right away. They may need to adjust your dose if it’s too high. Electrolyte imbalances can contribute to dizziness, so they may want to check your levels. Call 911 or have someone take you to the nearest ER if you feel like you’re going to pass out.

3. Weakness or fatigue

Feeling weak or tired when starting hydrochlorothiazide is common as your body adjusts to lower blood pressure. Sometimes, this tiredness can also be caused by low levels of important electrolytes, such as potassium, magnesium, or sodium.

Here’s what you can do to manage weakness and fatigue:

• Stay active. Regular exercise can help boost your energy levels.

• Eat well. Focus on a nutrient-rich, heart-healthy diet with foods high in electrolytes, such as bananas, spinach, and oranges.

• Monitor your blood pressure. Check it regularly to make sure it’s not too low, especially if you feel dizzy or weak.

• Talk to your healthcare team. If you feel unusually tired or weak, ask about getting an electrolyte blood test to check your levels.

• Seek medical help. Get emergency care if you have severe or persistent weakness, or if it’s accompanied by symptoms such as an irregular heartbeat or fainting.

4. Headache

Headaches are another possible side effect of hydrochlorothiazide, especially when you first start taking it. They often improve as your body adjusts to the medication. Even so, headaches can be bothersome and interfere with your daily activities. Here are a few tips for managing them:

• Stay hydrated. Dehydration is a common cause of headaches and can occur as your body loses extra fluid through urination. Aim to drink enough water throughout the day, unless you’ve been instructed to limit fluids.

• Try over-the-counter (OTC) pain relievers. Ask your healthcare team if it’s safe for you to take an OTC pain reliever, such as acetaminophen (Tylenol) for relief.

• Watch for other symptoms. Headaches could also signal an electrolyte imbalance. Let your prescriber know if you also feel dizzy or weak, or have muscle cramps.

• Contact your prescriber. If your headaches are severe, persistent, or getting worse, reach out to your prescriber. They can determine if your medication needs to be adjusted or changed.

5. Muscle cramps or spasms

Muscle cramps or spasms can happen with hydrochlorothiazide, often due to low potassium or magnesium levels. These imbalances can result from the way hydrochlorothiazide helps your body eliminate extra fluid and electrolytes.

If you’re experiencing muscle cramps, here’s what you should do:

• Don’t ignore symptoms. Muscle cramps, spasms, or twitching can signal that your electrolytes are out of balance. In more serious cases, you could develop an irregular heartbeat or other complications.

• Contact your prescriber. Let them know if you’re experiencing muscle cramps or spasms. They may recommend a blood test to check your potassium and magnesium levels.

• Ask about dietary changes. For mild cases, your prescriber may suggest increasing your intake of potassium-rich foods (such as bananas) or magnesium-rich foods (such as nuts, seeds, or whole grains).

• Follow supplement instructions. If advised, take potassium or magnesium supplements as directed. Don’t start them on your own without checking first.

• Know when to get emergency help. If you experience chest pain, a racing heartbeat, or confusion along with muscle cramps, seek emergency care right away.

6. High blood sugar levels

Hydrochlorothiazide can raise blood sugar levels in some people. This side effect can be especially problematic if you have diabetes. And it may increase the risk of developing diabetes if you have risk factors for it.

Here are a few tips for managing this side effect:

• Monitor your blood sugar regularly. If you already have diabetes, check your levels as recommended. Watch for symptoms of high blood sugar, such as increased thirst, blurred vision, and fruity-smelling breath.

• Report changes to your healthcare team. Tell them if your glucose levels rise or you notice new symptoms. They may need to adjust your diabetes medications. Don’t make any changes on your own without talking to them first.

• Be proactive about prevention. If you’re at risk for diabetes, your healthcare team may recommend periodic blood sugar checks while taking hydrochlorothiazide.

7. Erectile dysfunction and other sexual problems

Thiazide diuretics such as hydrochlorothiazide can cause sexual problems, including erectile dysfunction, trouble ejaculating, and decreased sex drive in some people. 

Many blood pressure medications can cause sexual dysfunction, but thiazides are among the most likely to cause these issues. It’s also important to remember that high blood pressure itself can also cause sexual problems.

Talk to your prescriber if you’re having sexual problems after starting hydrochlorothiazide. They can help determine the cause and best next steps, which may include switching to an alternative medication with fewer sexual side effects. Keep in mind that lifestyle factors also matter. Managing your body weight, quitting smoking, and exercising can improve sexual health.

8. Sensitivity to sunlight

While rare, hydrochlorothiazide could make your skin more sensitive to sunlight, making you more likely to have a sunburn-like reaction. In some cases, skin reactions can last even after you stop taking hydrochlorothiazide.

If you’re taking hydrochlorothiazide, be sure to protect yourself from direct sun exposure, because these skin reactions can increase your risk for cancer. You can lower your risk of sunburn and other skin-related side effects by using sunscreen, wearing protective clothing, and avoiding tanning.

9. Pancreatitis

Pancreatitis (inflammation of the pancreas) is a rare but severe side effect linked to hydrochlorothiazide. Symptoms of pancreatitis may include vomiting and severe pain in the upper and middle part of your abdomen. You may also have yellowing of the skin or eyes (jaundice).

Treatment for pancreatitis usually requires hospital care. Seek emergency medical care if you have any of these symptoms.

10. Vision problems

Although rare, hydrochlorothiazide has been linked to an eye condition called acute angle-closure glaucoma, which causes a dangerous increase in eye pressure.

Don’t ignore sudden vision changes after starting hydrochlorothiazide — early treatment can help protect your vision. Seek emergency care if you notice any of the following:

• Sudden blurry vision

• Eye pain or redness

• Headache with vision changes

• Seeing halos or rainbow-colored rings around lights

• Nausea or vomiting (along with eye symptoms)

Tell your prescriber if you’ve had vision problems in the past (especially glaucoma) before starting hydrochlorothiazide.

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Written by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

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