Thiazide diuretics are a common first-line choice for high blood pressure. They help your body remove extra salt and water, which lowers blood volume and eases pressure on blood vessels. Many people tolerate them well, and they're cheap and widely available — but a few simple rules help avoid problems.
Thiazides block salt reabsorption in the kidneys. That causes more urine and lowers blood pressure over days to weeks. Common drugs in this group include hydrochlorothiazide (HCTZ), chlorthalidone, indapamide, and metolazone. Doctors prescribe them for hypertension and sometimes for mild fluid retention (edema).
They can be used alone or with other blood pressure medicines. Chlorthalidone often stays active longer than HCTZ, so doctors sometimes prefer it for steady control. If you have heart failure, diabetes, or kidney issues, your doctor will pick the right type and dose for your situation.
Most side effects come from losing too much salt or shifting other electrolytes. Watch for frequent urination, muscle cramps, weakness, dizziness, or feeling faint when standing up. Thiazides can lower potassium and sodium and raise uric acid and blood sugar in some people.
Certain drugs change how thiazides work. Lithium levels can rise dangerously when combined with thiazides. NSAIDs (like ibuprofen) may reduce their blood-pressure benefit. Also mention them to your doctor if you take diabetes drugs, steroids, or strong heart medications — doses and monitoring may change.
Your doctor usually checks blood tests a few weeks after starting: potassium, sodium, creatinine, and sometimes glucose and uric acid. Older adults are more likely to get low sodium (hyponatremia), so labs and a careful dose are important.
Practical tips: take your pill in the morning to avoid nighttime bathroom trips. If your doctor adds potassium supplements or a potassium-sparing drug, follow dosing instructions — don't add OTC potassium without talking to them. If you feel dizzy, very weak, or have a fast heartbeat, call your provider. If you're pregnant, breastfeeding, or trying to get pregnant, check with your clinician before using thiazides.
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