Beta blockers are medicines that lower blood pressure. They also may be called beta-adrenergic blocking agents. The medicines block the effects of the hormone epinephrine, also known as adrenaline.

Beta blockers cause the heart to beat more slowly and with less force. This lowers blood pressure. Beta blockers also help widen veins and arteries to improve blood flow.

Some beta blockers mainly affect the heart. Other beta blockers affect both the heart and blood vessels. Several beta blockers are available. The best one for you depends on your health conditions.

Examples of beta blockers taken by mouth include:

• Acebutolol.
• Atenolol (Tenormin).
• Bisoprolol.
• Metoprolol (Lopressor, Toprol XL).
• Nadolol (Corgard).
• Nebivolol (Bystolic).
• Propranolol (Inderal LA, InnoPran XL).

Beta blockers are not recommended as a first treatment if you have only high blood pressure. Beta blockers are not usually used for high blood pressure unless other medicines, such as diuretics, have not worked well. A beta blocker may be one of several medicines used to lower blood pressure.

Beta blockers are used to prevent, treat or improve symptoms in other conditions, such as:

• Irregular heart rhythms, called arrhythmias.
• Heart failure.
• Chest pain, called angina.
• Heart attacks.
• Migraine.
• Some types of tremors.

Common side effects of beta blockers can include:

• Cold hands or feet.
• Extreme tiredness.
• Weight gain.
• Dizziness or light-headedness.

Less common side effects include:

• Depression.
• Shortness of breath.
• Trouble sleeping.

Beta blockers, especially ones that affect both the heart and blood vessels, generally are not used if you have asthma. There are concerns that the medicine may trigger severe asthma attacks.

If you have diabetes, beta blockers may block signs of low blood sugar, such as a rapid heartbeat. It's important to check your blood sugar regularly if you have diabetes and you're taking a beta blocker.

Some beta blockers can affect cholesterol and triglyceride levels. They can cause a slight rise in triglycerides, a type of fat in the blood. Beta blockers also can cause a modest decrease in good cholesterol, called high-density lipoprotein (HDL) cholesterol. These changes may only last for a short time.

You should not suddenly stop taking a beta blocker. Doing so could increase your risk of a heart attack or other heart problem.

Talk to your health care team if you have any questions about the medicines you take.