9 Hydrochlorothiazide Side Effects You Should Know About

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

But hydrochlorothiazide isn’t without its risks. Like any medication, it can be a delicate balancing act between hydrochlorothiazide side effects and benefits.

Hydrochlorothiazide side effects at a glance

Hydrochlorothiazide is well tolerated by most people. The most noticeable side effect for many people is peeing more, which is to be expected. This is how the medication works to remove fluid and salt from the body. 

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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.

Some of the more 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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More severe side effects can also occur. These are rare, but they’re still possible. Examples include:

• Pancreatitis

• Severely low sodium, magnesium, or potassium

• Kidney problems

• Eye problems

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

1. Electrolyte imbalances

Hydrochlorothiazide makes you pee more because it helps remove fluid from your body. This is beneficial because it helps lower your blood pressure and get rid of fluid buildup. But when fluid is removed, you may lose electrolytes as well.

Electrolytes are necessary for your body to function. Examples of electrolytes include sodium, potassium, and magnesium. Having the right balance of electrolytes helps everything run smoothly in the body. When electrolytes fall out of balance, side effects can occur.

If you take hydrochlorothiazide, 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. 

There are many symptoms that can be associated with low (or high) electrolyte levels. Examples include tiredness, dizziness, and muscle weakness. If you experience any of these symptoms after starting treatment with hydrochlorothiazide, talk to your healthcare provider. They may run a blood test to check your electrolyte levels to make sure they’re normal.

If you have low electrolytes, there might be a few things you can do. For example, if you have low sodium, your provider may recommend limiting your water intake, increasing the sodium in your diet, or switching to another diuretic. But before making any changes, talk to your provider.

2. Dizziness

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

To prevent dizziness, try to stay hydrated and get up slowly when you’re moving from a seated or lying down position to standing. You should also check your blood pressure regularly at home. This will help you to know if it drops too low. For most adults, low blood pressure is less than 90/60 mmHg. But that can vary from person to person.

If you check your blood pressure and it’s low, contact your healthcare provider. And if you have dizziness that doesn’t improve, reach out to your provider right away. Call 911 or have someone take you to the nearest emergency room if you feel like you’re going to pass out.

3. Weakness or fatigue

Hydrochlorothiazide can make you feel weak and tired, especially when you first start taking it and your body is adjusting to blood pressure changes. Weakness or fatigue can also be caused by electrolyte imbalances, such as low potassium, magnesium, or sodium levels. Exercising regularly and eating whole foods that are rich in electrolytes can help combat tiredness.

If you feel unusually tired, check your blood pressure to see if it’s low. Your healthcare provider may also recommend getting an electrolyte panel to see if your levels are low.

4. Headache

Another possible hydrochlorothiazide side effect is headaches. But these headaches may go away as your body adjusts to the medication. 

The reason hydrochlorothiazide causes headaches is unclear. Dehydration could be a factor, so make sure you’re drinking enough water while taking the medication. They could also be a sign of an electrolyte imbalance.

If you have headaches while taking hydrochlorothiazide, talk to your provider. They may recommend trying an over-the-counter pain reliever like ibuprofen (Advil, Motrin) or acetaminophen (Tylenol). These medications may help relieve headaches as your body adjusts to hydrochlorothiazide. But if your headaches don’t resolve or get worse at any point, let your healthcare provider know.

5. Muscle cramps or spasms

Some people may experience muscle cramps or spasms after taking hydrochlorothiazide. This may be due to a drop in potassium levels. Cases of low potassium levels (hypokalemia) can be mild or more serious. If you have mild hypokalemia, your healthcare provider may recommend increasing potassium in your diet or trying potassium supplements. If your case is more severe, you may need to stop taking hydrochlorothiazide and seek medical treatment, as there is a risk of serious side effects, including an irregular heartbeat.

Muscle spasms are also a possible symptom of low magnesium levels (hypomagnesemia). The treatment for hypomagnesemia can include increasing the amount of magnesium-rich foods in your diet or taking magnesium supplements. But more severe hypomagnesemia can be dangerous, resulting in seizures and confusion.

If you experience muscle cramps or spasms while taking hydrochlorothiazide, it’s best to let your provider know. They’ll probably want to order an electrolyte panel to see if your potassium or magnesium levels are low.

6. High blood sugar levels

Some studies have found that hydrochlorothiazide can raise blood glucose levels. This may cause hyperglycemia, which can be especially problematic for people living with diabetes. For people who don’t have diabetes but have risk factors, some research shows that taking hydrochlorothiazide can lead to diabetes.

If you have diabetes and take hydrochlorothiazide, your healthcare provider may have you check your blood glucose levels more frequently. You should also keep an eye out for symptoms of hyperglycemia. These include feeling thirstier than normal and going to the bathroom frequently. If you experience any of the symptoms of hyperglycemia, or if your blood glucose levels are higher than usual, let your provider know.

If you take diabetes medications (including insulin), you may need a different dosage once you start taking hydrochlorothiazide. But don’t make any changes to your medication regimen without talking to your provider first.

7. Sexual problems

Thiazides can cause sexual problems, including erectile dysfunction, trouble ejaculating, and decreased sex drive in some people.

While many blood pressure medications can cause sexual problems, thiazides are one of the most likely medication groups to do so. If you’re having sexual problems after starting treatment with hydrochlorothiazide, talk to your healthcare provider. They may recommend another blood pressure medication or another type of diuretic that’s less likely to cause these side effects.

Good to know: High blood pressure itself can also cause sexual problems. And thiazides are a first-choice option for high blood pressure. So if you’re taking hydrochlorothiazide and having sexual problems, don’t stop taking it without talking to your provider first.

8. Sensitivity to sunlight

While rare, hydrochlorothiazide could make your skin more sensitive to sunlight. Research has found that diuretics like hydrochlorothiazide can make people more likely to have a sunburn-like response to sunlight. In some cases, skin reactions can last even after a person stops taking hydrochlorothiazide.

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

9. Pancreatitis

A rare but severe side effect of hydrochlorothiazide is pancreatitis. This is a sudden inflammation of the pancreas. And it can be caused by hydrochlorothiazide building up in the body to a point that it’s toxic. 

Symptoms of pancreatitis may include vomiting and severe pain in the upper and middle part of your abdomen. You may also experience yellowing of the skin or eyes (jaundice). Treatment for pancreatitis usually requires hospital care. So if you have any of these symptoms, seek emergency care.

When should you contact your healthcare provider about hydrochlorothiazide side effects?

If you have hydrochlorothiazide side effects that are bothersome or don’t go away, reach out to your healthcare provider. They can guide you on how to safely address your symptoms. 

It’s important that you don’t stop taking hydrochlorothiazide abruptly. This can lead to elevated blood pressure or a fast heart rate. Your healthcare provider can help you stop taking hydrochlorothiazide safely, if needed.

If you’re experiencing severe symptoms after starting hydrochlorothiazide — like extreme dizziness, weakness, or vomiting — it’s best to seek emergency medical care right away.

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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.

Reviewed 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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