Before taking hydrochlorothiazide, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients (such as sulfites found in some brands), which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: diabetes, gout, kidney disease, liver disease, lupus, skin cancer.

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Severe sweating, diarrhea, or vomiting may cause dehydration and cause you to feel lightheaded. Tell your doctor if you have severe diarrhea or vomiting. To prevent dehydration, drink plenty of fluids unless your doctor tells you not to.

If you have diabetes, hydrochlorothiazide may affect your blood sugar. Check your blood sugar regularly as directed by your doctor. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

This drug may decrease your potassium levels. Ask your doctor about foods high in potassium (such as bananas, orange juice) or about using a salt substitute containing potassium. A potassium supplement may be prescribed by your doctor.

This medication may make you more sensitive to the sun. It may also increase your risk for skin cancer, especially if you take it for a long time. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned, have skin blisters/redness, or notice new or changed moles/skin lesions.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the effects of this drug, especially dizziness.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This drug passes into breast milk, but is unlikely to harm a nursing infant. Consult your doctor before breastfeeding.