Atenolol belongs to a group of medicines called beta blockers.

It's used to treat high blood pressure and irregular heartbeats (arrhythmia).

It can also be used to prevent chest pain caused by angina.

If you have high blood pressure, taking atenolol helps prevent future heart disease, heart attacks and strokes.

Atenolol is sometimes prescribed to prevent migraines and help with anxiety. But it's not officially approved to treat these conditions.

This medicine is only available on prescription.

It comes as tablets or as a liquid that you swallow. It can also be given as an injection, but this is usually done in hospital.

• Atenolol slows down your heart rate and makes it easier for your heart to pump blood around your body.
• It can make you feel dizzy, sick or tired, or give you constipation or diarrhoea. These side effects are usually mild and short-lived.
• Your very first dose of atenolol may make you feel dizzy, so take it at bedtime. After that, if you do not feel dizzy, you can take it in the morning.
• Do not stop taking atenolol suddenly, especially if you have heart disease. This can make your condition worse.
• Atenolol is known by the brand name Tenormin. Other brand names include Tenif (for atenolol mixed with nifedipine) and Co-tenidone (atenolol mixed with chlortalidone).

Atenolol can be taken by adults. It's sometimes also prescribed for babies and children.

It's not suitable for everyone. To make sure it's safe for you, tell your doctor before starting atenolol if you have:

• had an allergic reaction to atenolol or any other medicine in the past
• low blood pressure or a slow heart rate
• serious blood circulation problems in your limbs (such as Raynaud's phenomenon), which may make your fingers and toes tingle or turn pale or blue
• metabolic acidosis - when there's too much acid in your blood
• lung disease or asthma

Tell your doctor if you're trying to get pregnant, are already pregnant or breastfeeding.

You'll usually take atenolol once or twice a day.

When you start taking atenolol, your doctor may advise you to take your first dose before bedtime because it can make you feel dizzy.

After the first dose, if you do not feel dizzy, you can take your medicine in the morning.

If you're taking atenolol twice a day, you'll usually have 1 dose in the morning and 1 dose in the evening.

It's a good idea to leave 10 to 12 hours between doses if you can.

Do not stop taking atenolol suddenly, especially if you have heart disease. This can make your condition worse.

If you want to stop taking your medicine, speak to your doctor. They may recommended reducing your dose gradually over a few weeks.

How much will I take?

How much you take depends on why you need atenolol.

• For high blood pressure - the usual dose is 25mg to 50mg taken once a day.
• For angina (chest pain) - the usual dose is 100mg taken once a day, or split into 2 50mg doses.
• For irregular heartbeats (arrhythmia) - the usual dose is 50mg to 100mg taken once a day.
• For migraine - the usual dose is 25mg to 100mg taken twice a day. Doctors sometimes prescribe atenolol for migraine, but it's not officially approved for preventing it.

For children taking atenolol, your child's doctor will work out the right dose by using their weight and age.

How to take it

Atenolol does not usually upset your tummy, so you can take it with or without food. It's best to do the same each day.

Swallow the tablets whole with a drink of water.

If you find them difficult to swallow, some brands have a score line to help you break the tablet in half. Check the information leaflet for your brand to see if you can do this.

If you're taking atenolol as a liquid, it'll come with a plastic syringe or spoon to help you measure out the right dose.

If you do not have one, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not give you the right amount of medicine.

What if I forget to take it?

If you forget to take a dose of atenolol, take it as soon as you remember, unless it's nearly time for your next dose. In this case, just leave out the missed dose and take your next dose as normal.

Never take 2 doses at the same time. Do not take an extra dose to make up for a forgotten one.

If you often forget doses, it may help to set an alarm to remind you.

You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

The amount of atenolol that can lead to an overdose varies from person to person.

Like all medicines, atenolol can cause side effects in some people, but many people have no side effects or only minor ones.

Side effects often improve as your body gets used to the medicine.

Common side effects

These common side effects happen in more than 1 in 100 people. They're usually mild and short-lived.

Talk to your doctor or pharmacist if these side effects bother you or last more than a few days:

• feeling sleepy, tired or dizzy
• cold fingers or toes
• feeling sick (nausea)
• diarrhoea
• constipation

Serious side effects

It happens rarely, but some people have serious side effects when taking atenolol.

Tell a doctor straight away if you have:

• shortness of breath with a cough that gets worse when you exercise (like walking up stairs), swollen ankles or legs, chest pain, or an irregular heartbeat - these can be signs of heart problems
• trouble breathing, cold sweats and sudden, sharp chest pain that gets worse when you cough or take deep breaths - these can be signs of lung problems
• a fast heart rate, a high temperature, trembling and confusion - these can be signs of a thyroid problem

Serious allergic reaction

In rare cases, atenolol may cause a serious allergic reaction (anaphylaxis).

These are not all the side effects of atenolol.

For a full list, see the leaflet inside your medicine packet.

What to do about:

• feeling sleepy, tired or dizzy - as your body gets used to atenolol, these side effects should wear off. If atenolol makes you feel dizzy, sit or lie down until you feel better. Do not drive or operate machinery until you feel OK again. Try to avoid alcohol as it'll make you feel worse.
• cold fingers or toes - put your hands or feet under warm running water, massage them and wiggle your fingers and toes. Do not smoke or have drinks with caffeine in - this can make your blood vessels narrower and further restrict blood flow to your hands and feet. Try wearing mittens (they're warmer than gloves) and warm socks. Do not wear tight watches or bracelets.
• feeling sick (nausea) - stick to simple meals and do not eat rich or spicy food. It might help to take your atenolol after a meal or snack.
• diarrhoea - drink lots of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
• constipation - eat more high-fibre foods, such as fresh fruit, vegetables and cereals, and drink plenty of water. Try to exercise more regularly by going for a daily walk, for example. If this does not help, talk to your pharmacist or doctor. Watch this short video about how to treat constipation

Atenolol is not usually recommended in pregnancy.

If you're trying to get pregnant or already pregnant, talk to your doctor about the benefits and possible harms of taking atenolol.

There may be other medicines that are safer for you. Labetalol is a similar medicine that's often recommended for high blood pressure in pregnancy.

For more information about how atenolol can affect you and your baby during pregnancy, visit the best use of medicines in pregnancy (BUMPS) website.

Atenolol and breastfeeding

If your doctor or health visitor says that your baby's healthy, it's OK to take atenolol while breastfeeding.

Atenolol passes into breast milk in small amounts, and it's unlikely to cause any side effects in your baby.

It's important to treat your high blood pressure to keep you well. Breastfeeding will also benefit both you and your baby.

If your baby's not feeding as well as usual or seems unusually sleepy, or you have any other concerns about them, talk to your doctor or health visitor.

They may recommend a different medicine for your blood pressure.

There are some medicines that may interfere with the way atenolol works.

Tell your doctor if you're taking:

• other medicines for high blood pressure - the combination with atenolol can sometimes lower your blood pressure too much, which may make you feel dizzy or faint; tell your doctor if this keeps happening to you, as they may change your dose
• other medicines for an irregular heartbeat, such as amiodarone or flecainide
• medicines for asthma or chronic obstructive pulmonary disease (COPD)
• medicines for diabetes, particularly insulin - atenolol may make it more difficult to recognise the warning signs of low blood sugar; speak to your doctor if you have low blood sugar levels without getting any of the usual warning signs (you should check your blood sugar after exercise and follow the usual advice about checking it before driving or operating machinery)
• medicines to treat nose or sinus congestion, or other cold remedies (including those you can buy in a pharmacy)
• medicines for allergies, such as ephedrine, noradrenaline or adrenaline

Mixing atenolol with herbal remedies or supplements

There's very little information about taking herbal remedies and supplements with atenolol.