Before taking this product, tell your doctor or pharmacist if you are allergic to atenolol or chlorthalidone; or if you have any other allergies. This product may contain inactive ingredients, 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: liver disease, kidney disease, certain types of heart rhythm problems (such as a slow heartbeat, second- or third-degree atrioventricular block), gout, lupus, breathing problems (such as asthma, chronic bronchitis, emphysema), blood circulation problems (such as Raynaud's disease, peripheral vascular disease), untreated mineral imbalance (such as low potassium), serious allergic reactions including those needing treatment with epinephrine, a certain muscle/nerve disease (myasthenia gravis).

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.

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

This medication may reduce the potassium levels in your blood. Ask your doctor about adding potassium to your diet. Your doctor may prescribe a potassium supplement.

This product may prevent the fast/pounding heartbeat you would usually feel when your blood sugar level falls too low (hypoglycemia). The risk is higher if you have diabetes, or are vomiting, fasting, or not eating regularly. Other symptoms of low blood sugar level, such as dizziness and sweating, are not affected by this drug.

If you have diabetes, this product may make it harder to control your blood sugar levels. Check your blood sugar levels regularly as directed by your doctor. Tell your doctor right away if you have symptoms of high blood sugar such as increased thirst/urination. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

This medication may make you more sensitive to the sun. 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 or have skin blisters/redness.

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

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using this medication. Atenolol may harm an unborn baby. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

Atenolol and chlorthalidone pass into breast milk. Atenolol may harm a nursing infant. Consult your doctor before breastfeeding.