Do NOT use Hydrochlorothiazide if:

• you are allergic to any ingredient in Hydrochlorothiazide
• you are unable to urinate
• you are taking dofetilide or ketanserin.

Contact your doctor or health care provider right away if any of these apply to you.

Some medical conditions may interact with Hydrochlorothiazide. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have had a severe allergic reaction (eg, rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue) to a sulfonamide medicine (eg, sulfamethoxazole)
• if you have gout, liver problems, (eg, cirrhosis), lupus, kidney problems, diabetes, asthma, parathyroid gland problems, or high blood cholesterol or lipid levels
• if you have high or low blood electrolyte levels (eg, sodium, potassium, magnesium, calcium)
• if you are taking another medicine for high blood pressure.

Some medicines may interact with Hydrochlorothiazide. Tell your health care provider if you are taking any other medicines, especially any of the following:

• Digoxin, dofetilide, or ketanserin because the risk of irregular heartbeat may be increased
• Barbiturates (eg, phenobarbital), corticotropin, corticosteroids (eg, prednisone), or narcotic pain medicines (eg, codeine) because they may increase the risk of Hydrochlorothiazide's side effects
• Cholestyramine, colestipol, or nonsteroidal anti-inflammatory medicines (NSAIDs) (eg, ibuprofen) because they may decrease Hydrochlorothiazide's effectiveness
• Diazoxide or lithium because the risk of their side effects may be increased by Hydrochlorothiazide
• Diabetes medicines (eg, glipizide, metformin) or insulin because their effectiveness may be decreased by Hydrochlorothiazide.

This may not be a complete list of all interactions that may occur. Ask your health care provider if Hydrochlorothiazide may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

Important safety information:

• Hydrochlorothiazide may cause dizziness or blurred vision. These effects may be worse if you take it with alcohol or certain medicines. Use Hydrochlorothiazide with caution. Do not drive or perform other possible unsafe tasks until you know how you react to it.
• Hydrochlorothiazide may cause dizziness, lightheadedness, or fainting; alcohol, hot weather, exercise, or fever may increase these effects. To prevent them, sit up or stand slowly, especially in the morning. Sit or lie down at the first sign of any of these effects.
• Your doctor may also prescribe a potassium supplement for you. If so, take the potassium supplement exactly as prescribed. Do not start taking additional potassium on your own or change your diet to include more potassium without first checking with your doctor.
• Tell your doctor or dentist that you take Hydrochlorothiazide before you receive any medical or dental care, emergency care, or surgery.
• Tell your doctor if you will be exposed to high temperatures. The risk of certain side effects (eg, low blood sodium levels) may be increased in hot weather.
• Hydrochlorothiazide may cause you to become sunburned more easily. Avoid the sun, sunlamps, or tanning booths until you know how you react to Hydrochlorothiazide. Use a sunscreen or wear protective clothing if you must be outside for more than a short time.
• Patients who take medicine for high blood pressure often feel tired or run down for a few weeks after starting treatment. Be sure to take your medicine even if you may not feel "normal." Tell your doctor if you develop any new symptoms.
• Hydrochlorothiazide may raise your blood sugar. High blood sugar may make you feel confused, drowsy, or thirsty. It can also make you flush, breathe faster, or have a fruit-like breath odor. If these symptoms occur, tell your doctor right away.
• Diabetes patients - Check blood sugar levels closely. Ask your doctor before you change the dose of your diabetes medicine.
• Hydrochlorothiazide may interfere with certain lab tests, including parathyroid function tests. Be sure your doctor and lab personnel know you are taking Hydrochlorothiazide.
• Lab tests, including kidney function, blood pressure, and electrolyte levels, may be performed while you use Hydrochlorothiazide. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
• Use Hydrochlorothiazide with caution in the elderly; they may be more sensitive to its effects, especially dizziness.
• Pregnancy and breast-feeding: Hydrochlorothiazide may cause harm to the fetus. If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using Hydrochlorothiazide while you are pregnant. Hydrochlorothiazide is found in breast milk. If you are or will be breast-feeding while you use Hydrochlorothiazide, check with your doctor. Discuss any possible risks to your baby.

All medicines may cause side effects, but many people have no, or minor, side effects.

Check with your doctor if any of these most common side effects persist or become bothersome:

Constipation; diarrhea; dizziness; lightheadedness (especially when sitting up or standing); loss of appetite; nausea; temporary blurred vision.

Seek medical attention right away if any of these severe side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); confusion; dark urine; decreased urination; fainting; fast or irregular heartbeat; fever, chills, or persistent sore throat; increased thirst; joint pain, swelling, warmth, or redness (especially of the big toe joint); mental or mood changes; muscle pain or cramps; numbness or tingling; red, swollen, blistered, or peeling skin; seizures; severe or persistent dizziness; severe or persistent nausea or stomach pain; shortness of breath; unusual bruising or bleeding; unusual drowsiness, restlessness, tiredness, or weakness; unusually dry mouth; vomiting; yellowing of the eyes or skin.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.