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Key takeaways
Hydrochlorothiazide (HCTZ) is a diuretic medication primarily used to treat high blood pressure and edema, which works by increasing the elimination of water and salt through urine.
Common side effects of hydrochlorothiazide include electrolyte imbalances like low potassium and sodium levels, increased sun sensitivity leading to a higher risk of certain skin cancers, and potential for serious allergic or skin reactions.
Long-term or serious side effects can include dangerously low potassium levels, kidney dysfunction or failure, and an increased risk of non-melanoma skin cancer, particularly in patients with white skin.
To minimize side effects, patients are advised to follow prescription directions carefully, avoid excessive sun exposure and use sunscreen, stay hydrated, and regularly consult healthcare providers for follow-up tests and appointments.
Hydrochlorothiazide (HCTZ) is a generic drug prescribed to lower blood pressure. It is also used to reduce swelling of the legs due to congestive heart failure, ascites, or treatment with corticosteroids or estrogen. As a thiazide diuretic (water pill), hydrochlorothiazide increases the elimination of water and salt in the urine. This helps to decrease blood pressure. Many of hydrochlorothiazide’s side effects are due to its diuretic effects. Some side effects are avoidable, some can be minimized, and others may require medical intervention.
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Common side effects of hydrochlorothiazide
The most common side effect of hydrochlorothiazide is low potassium levels, a direct effect of the drug’s diuretic effects. Anywhere from one-third to half of people taking hydrochlorothiazide will eventually develop low potassium levels (as indicated on a blood lab report). Many of the other common side effects are also related to the body’s increased elimination of water and electrolytes:
- Low potassium
- Low sodium
- Low magnesium
- Elevated calcium
- Low chloride
- Elevated blood sugar
- Elevated cholesterol and fat levels
- Elevated uric acid levels
- Orthostatic hypotension (dizziness and vertigo when standing)
- Dizziness
- Diarrhea
- Abdominal pain
- Weakness
- Headache
- Hair loss
- Rash
Serious HCTZ side effects
Hydrochlorothiazide’s most serious side effects include:
- Dangerously low potassium levels
- Electrolyte imbalance
- Sun sensitivity
- Abnormal heartbeats
- Inflamed pancreas
- Skin cancer
- Kidney dysfunction
- Kidney failure
- Anemia
- Low white blood cell counts (which decreases the body’s ability to fight infection)
- Low platelet levels (which can cause easy bruising or bleeding)
- Angle-closure glaucoma
- Worsening of lupus
- Severe allergic reactions or serious skin reactions
Weight changes
Hydrochlorothiazide eliminates more water from the body than usual, which can lead to a decrease in body weight. That’s nice to see on a bathroom scale, but it isn’t fat or muscle weight. It’s water weight. When hydrochlorothiazide is stopped, the water weight will probably return in short order.
Electrolyte imbalance
Electrolyte imbalances are a common and may be a serious side effect of hydrochlorothiazide. The drug can deplete the body of one or more electrolytes including sodium, potassium, magnesium, and chloride. It can also increase calcium levels. The effects seem to be dose-related. While the incidence of electrolyte problems has not been determined, they are common enough that people taking hydrochlorothiazide need to be periodically tested for electrolyte levels, particularly potassium with a common blood test. People taking hydrochlorothiazide should know the signs of electrolyte depletion, particular hypokalemia, or low potassium, such as weakness, fatigue, muscle cramps, and constipation. Contact a healthcare professional if any of these symptoms are noticed.
Sun sensitivity
Hydrochlorothiazide is associated with an increased risk of certain skin cancers. The medication causes sun sensitivity. Patients who take hydrochlorothiazide should visit their dermatologist on a regular basis for skin cancer screenings. Also, people who take this drug should avoid tanning beds, and avoid the sun when possible. When in the sun, it is important to wear protective clothing and apply and reapply sunscreen (of at least SPF 30) frequently.
Severe allergic or skin reactions
In rare cases, a serious allergic or skin reaction may occur. These reactions can be life-threatening or cause death. If you notice any of the following symptoms, get emergency medical help right away. Symptoms of a serious allergic reaction can include hives, difficulty breathing, or swelling of the face, lips, tongue, or throat. Symptoms of a serious skin reaction may include sore throat, fever, burning eyes, red or purple rash, or blistering or peeling skin.
Chest pain
Hydrochlorothiazide has not been associated with causing or worsening chest pain. However, it is frequently combined with other blood pressure drugs that may worsen chest pain. When taking more than one prescription drug, it’s sometimes difficult to determine which drug is responsible for individual side effects. Chest pain is a potentially serious symptom, so make sure to tell the prescribing healthcare provider.
Joint pain
Joint pain is not a side effect of hydrochlorothiazide. However, the drug can worsen some types of existing joint diseases. Because hydrochlorothiazide reduces the fluid volume of blood, it results in a percentage increase of other substances in the blood like uric acid. If uric acid levels get high enough, the excess crystallizes in the joints. This can cause or worsen gout, an arthritic condition due to uric acid crystals building up in the joints. How often hydrochlorothiazide contributes to gout flare-ups is unknown, but the joint pain is certainly painful and sometimes debilitating.
Hair loss
Thinning hair is a side effect of thiazide diuretics. The hair loss won’t happen all at once as it does with some drugs, such as cancer drugs. Instead, it will take a few months. The incidence is unknown, but remember that hydrochlorothiazide is typically used with other blood pressure drugs. One type of blood pressure drug, beta blockers, are also associated with hair loss and hair thinning. The good news is that drug-induced hair loss is usually reversible once the offending drug has been stopped.
Hydrochlorothiazide side effects by dosage
Hydrochlorothiazide is usually dosed once daily or sometimes twice daily. Increased daily dosage of hydrochlorothiazide can increase the risk of electrolyte disturbances and dehydration. When given for hypertension, HCTZ doses are rarely above 50 mg a day. However, when used for the treatment of swelling of extremities, HCTZ doses may be as high as 100 mg per day, which increases the risk of side effects.
How soon do hydrochlorothiazide side effects start?
Hydrochlorothiazide’s diuretic effects begin within an hour or two of taking the capsule or tablet and peak in one to five hours. Some side effects may occur during this time, including diarrhea, nausea, and vomiting. Allergic reactions, however, can occur very rapidly, even after taking the first dose. Many other side effects are delayed and could take days, weeks, or months to manifest.
How long do hydrochlorothiazide side effects last?
The body will adapt to hydrochlorothiazide, so some side effects may lessen over time as you get used to the medicine. Those that don’t will mostly resolve after the drug has been stopped, particularly the most common side effects. Even hair loss is often reversible when caused by drugs like hydrochlorothiazide.
What are the long-term side effects of hydrochlorothiazide?
Most of hydrochlorothiazide’s side effects will get better after the drug has been stopped. Some conditions may require time to improve, such as allergic reactions or gout. Some side effects, such as skin cancer or kidney damage, may have long-term or lifelong consequences.
Hydrochlorothiazide contraindications
You should not take hydrochlorothiazide if you have:
- Kidney problems or can’t make urine
- An allergy to hydrochlorothiazide or sulfa drugs
- A newborn with jaundice (if breastfeeding)
Use caution or talk to your provider if you’re pregnant, breastfeeding, or taking other medications.
Hydrochlorothiazide warnings
Like all diuretics, hydrochlorothiazide may cause problems due to pre-existing health conditions or other underlying issues.
Cautions
Hydrochlorothiazide can cause problems in people with certain medical conditions. In some cases, hydrochlorothiazide may worsen conditions such as gout or trigger a recurrence, like pancreatitis. These medical or physical conditions include:
- Diabetes
- Electrolyte problems
- Dehydration
- A history of gout
- A history of pancreatitis
- Liver or kidney problems
- Irregular heartbeats
- A history of seizures
- Lupus
Additionally, hydrochlorothiazide may cause issues in older patients, including low sodium levels and falls. Finally, the risk for non-melanoma skin cancer goes up when taking hydrochlorothiazide, a risk that is greatest for caucasian patients.
Abuse and dependence
Hydrochlorothiazide is not associated with drug abuse, dependence, or withdrawal.
Overdose
A hydrochlorothiazide overdose can cause a hazardous depletion of electrolytes, so immediate medical care is needed if an overdose is suspected. The symptoms of an overdose may include:
- Nausea
- Dizziness
- Weakness
- Muscle pain
- Dry mouth/thirst
The maximum dosage will depend on age and the condition being treated. The maximum adult dose for hypertension is 50 mg per day; for fluid retention, the maximum daily dose is 100 mg.
Recalls
Hydrochlorothiazide recalls are rare and limited to quality issues at individual manufacturing centers.
Hydrochlorothiazide interactions
People using hydrochlorothiazide often take other drugs. Some of these can be risky when taken with hydrochlorothiazide:
- Other blood pressure medications, though commonly prescribed with hydrochlorothiazide, increase the risk of low blood pressure
- Corticosteroids such as prednisone increase the risk of electrolyte loss when taking thiazide diuretics
- Bile resins (such as cholestyramine) can make it harder for the body to absorb hydrochlorothiazide
- Antidiabetic drugs may be less effective because thiazide diuretics can increase blood sugar levels
- Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, and naproxen may reduce the effectiveness of hydrochlorothiazide and increase the risk of kidney damage
- Some drugs, like aminoglycoside antibiotics and lithium, can damage the kidneys; they are more likely to damage the kidneys when taken with a diuretic
- Barbiturates, sedatives, and opioids increase the risk of orthostatic hypotension and, as a result, may increase the risks of accidents, fainting, and falls
- Stimulants (such as Adderall) can increase blood pressure, which may decrease the effectiveness of hydrochlorothiazide in lowering blood pressure
- Marplan (isocarboxazid), an antidepressant in the monoamine oxidase inhibitor (MAOI) drug class, is never given with drugs that lower blood pressure, because the combination could cause a dangerous drop in blood pressure. Other medications in the MAOI class can have the same effect and should not be taken with hydrochlorothiazide
Foods and drinks to avoid when taking hydrochlorothiazide include alcohol, excessive amounts of caffeine, and diuretic herbs like dandelion, hibiscus, or green tea.
How to avoid hydrochlorothiazide side effects
Diuretics like hydrochlorothiazide often involve unwanted adverse effects, but they are important tools in fighting high blood pressure. A few guidelines can help both to minimize side effects and maximize the drug’s benefits.
1. Take hydrochlorothiazide as directed
Follow all directions provided by the prescriber or printed on the prescription label. The standard dose is 12.5–50 mg per day for hypertension and 25–100 mg daily for edema. Generally, it is best to take hydrochlorothiazide in the morning. This is because it makes you urinate, and taking it at night may disrupt your sleep.
What if you miss a dose of hydrochlorothiazide? If a dose is missed, take it as soon as you remember. However, if it’s almost time for the next dose, skip the missed dose and continue with your regular schedule. Take the next scheduled dose at the regular time. Do not double the dose to try to make up for a missed dose.
2. Give the prescriber a complete medical history
The most worrisome side effects involve worsening existing medical conditions, so make sure the prescribing healthcare provider has an entire medical history, especially:
- Kidney disease
- Liver disease
- Gout
- Diabetes
- Low potassium
- High calcium
- Narrow angles in the eyes or a history of glaucoma
- Seizure disorders
- Heart rate problems
- Any upcoming parathyroid tests
- Pregnancy, anticipated pregnancy, or breastfeeding
3. Give the prescriber a list of all drugs being taken
Drug interactions are another significant source of side effects, so make sure the prescribing healthcare provider has a complete picture of the prescription drugs, over-the-counter medications, and vitamins or dietary supplements being taken, particularly:
- Blood pressure medications
- Corticosteroids
- Bile resins such as cholestyramine or colestipol
- Lithium
- NSAIDs
4. Do not miss follow-up appointments or lab tests
Staying safe on diuretics may require follow-up visits and tests. In this way, side effects can be corrected before they become hazardous.
5. Drink plenty of fluids
To avoid dehydration, drink plenty of clear (not salty) fluids throughout the day. Avoid going outside if it’s hot. If hydrochlorothiazide is being used to treat fluid retention, follow the fluid restrictions given by the prescribing healthcare provider.
6. Avoid laxatives
Laxatives can cause dehydration. The risk is even greater when taking diuretics. The best advice is not to use laxatives casually when taking diuretics. If constipation is a problem, consult a healthcare provider for the most suitable treatment.
7. Skip the calcium supplements
Hydrochlorothiazide can increase calcium levels in the body. If you are taking calcium or vitamin D supplements, discuss with your prescriber whether to continue them.
8. Avoid taking a late dose
Hydrochlorothiazide can be taken at any time of day, but if taken late, it could interfere with sleep by requiring frequent trips to the bathroom. Most people prefer to take hydrochlorothiazide in the morning.
9. Use sunblock
Hydrochlorothiazide increases the risk of developing non-melanoma skin cancer. That risk approximately triples for people with fair skin. Avoid the sun. If it’s unavoidable, use a high SPF sunscreen and reapply it frequently, especially when swimming and/or sweating.
How to treat side effects of hydrochlorothiazide
If you notice any of these symptoms, here’s what to do:
- Dizziness: Sit or lie down immediately. Stand up slowly.
- Dehydration: Sip water or electrolyte drinks and call your provider.
- Electrolyte issues: Be aware of muscle cramps, fatigue, or irregular heartbeats. Contact a provider.
- Vision changes or eye pain: Get emergency help immediately.
- Allergic reactions: Seek emergency care for swelling, hives, or skin blistering
When to see your healthcare provider about HCTZ side effects
Symptoms that require immediate medical attention include:
- Severe dizziness
- Chest pain
- Severe cramping during the day or that wakes you at night
- Seizures
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