ACE inhibitors and angiotensin II receptor blockers

Expert reviewer Dr Tim Cripps, Consultant Cardiologist
Next review due May 2022

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) are medicines which widen your blood vessels and so lower your blood pressure. They’re often used to treat high blood pressure, and heart and kidney problems.

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Uses of ACE inhibitors and ARBs

Your doctor may recommend you take an ACE inhibitor or an ARB to lower your blood pressure if you have:

It’s important to be aware that these medicines aren’t suitable for everyone. You should discuss any other medical conditions or medicines that you take with your doctor. If you’re a woman and hoping to become pregnant or are breastfeeding, let your doctor know as they’ll need to take this into consideration.

It’s your choice whether to take a medicine or not. Before making a decision, make sure you have discussed your options and the pros and cons of taking the medicine with your doctor.

How ACE inhibitors and ARBs work

ACE inhibitors and ARBs lower your blood pressure and make it easier for your heart to pump blood round your body.

They do this by affecting one of the systems your body has for controlling your blood pressure. When your blood pressure drops too low, your body produces a chemical called angiotensin I. An enzyme called angiotensin-converting enzyme (ACE) converts (changes) this into angiotensin II. Angiotensin II narrows your blood vessels and triggers the release of a hormone which makes your body hold on to water. The extra volume of fluid in your blood and the narrowing of your blood vessels make your blood pressure rise again.

Here’s how ACE inhibitors and ARBs work on this system.

  • ACE inhibitors block the action of angiotensin-converting enzyme so that angiotensin I isn't converted to angiotensin II.
  • ARBs block the action of angiotensin II. You may also see these medicines called angiotensin II receptor ‘antagonists’.

If you have kidney disease, as well as lowering your blood pressure ACE inhibitors and ARBs can also help your kidneys work better for longer.

Types of ACE inhibitors and ARBs

There are lots of different ACE inhibitors (for example enalapril and ramipril) and ARBs (for example candesartan and losartan). They probably work as well as each other, with ARBs giving fewer side-effects. Your doctor will normally decide which is best for you after considering a number of factors. These include what condition you have, whether you have any other medical problems, and the cost. Most people will be offered an ACE inhibitor first. If this causes a troublesome cough, your doctor may offer you an ARB instead.

If you want to know more about why a particular medicine has been prescribed, ask your doctor.

Taking ACE inhibitors and ARBs

You’ll usually need to take ACE inhibitors or ARBs on a long-term basis, with on-going monitoring. Your doctor will ask you to have a blood test before you start taking these medicines. They’ll test you again a week or two after you first start taking the medicine, or if they increase your dose. After this, your doctor will test you every year. These tests are to check that your kidneys are healthy, and that your blood pressure is responding well to your medicine. It’s very important that you have these blood tests.

You take ACE inhibitors or ARBs as tablets, usually once a day. When you have your first dose, your doctor may advise you that it’s best to take it at night. If everything is well and you don’t get bad side-effects, you can take the tablets every morning. Your doctor may start you on a low dose, then increase this gradually over a few weeks or months to reach the most effective dose.

The patient information leaflet that comes with your medicine will tell you more about how to take your tablets. You should read it carefully. With some tablets it’s important not to crush or chew them, just swallow them whole with a drink of water. If you have any questions or concerns about taking your medicine, ask your pharmacist.

Interactions of ACE inhibitors and ARBs

ACE inhibitors and ARBs can interact with other medicines to cause unwanted effects. For instance, some medicines, when taken together with ACE inhibitors or ARBs can give you very low blood pressure (hypotension) or very high potassium levels in your blood. The same effect can happen if you take both ACE inhibitors and ARBs together, so this isn’t usually advised.

Check with your doctor or pharmacist before you take any other medicines or supplements at the same time as ACE inhibitors or ARBs.

For more information about drinking alcohol while taking ACE inhibitors or ARBs, see our FAQ: Can I drink alcohol with ACE inhibitors or ARBs?

Side-effects of ACE inhibitors and ARBs

Like all medicines, ACE inhibitors and ARBs can cause side-effects for some people. Possible side-effects include:

  • low blood pressure, which may cause dizziness
  • a persistent dry cough if you take ACE inhibitors (you don’t usually get this side-effect with ARBs)
  • your kidneys not working as well as they did before
  • headaches
  • abdominal (tummy) discomfort, diarrhoea, constipation, feeling sick or vomiting

We haven’t included all the possible side-effects here. Your patient information leaflet will have more information about side-effects and how common they are. ARBs usually have milder side-effects than ACE inhibitors.

If you get these or other side-effects with ACE inhibitors, contact your doctor. They may suggest reducing your dose or changing to another medicine.

Medicines checklist

Our handy medicines checklist helps you see what to check for before taking a medicine.

Bupa's medicines checklist PDF opens in a new window (0.8MB)

Bupa medicines checklist

Frequently asked questions

  • Low blood pressure is a common side-effect in people taking ACE inhibitors and ARBs and drinking alcohol makes this even more likely to happen. It can be dangerous if your blood pressure drops too much – you might feel dizzy and even fall. If you’re taking an ACE inhibitor or an ARB, check the patient leaflet to see if it gives advice about drinking alcohol. If you still have queries, ask a pharmacist or your doctor.

  • Having diabetes can damage your kidneys. If you have diabetes, and early signs of kidney problems, your doctor will probably recommend you take an ACE inhibitor or an ARB. That’s because these medicines can help protect your kidneys and keep them working as well as possible.

    ACE inhibitors or ARBs are also the usual first choice treatment if you have high blood pressure as well as diabetes. High blood pressure can cause further damage to your kidneys, so it’s especially important to keep your blood pressure under control if you have diabetes.

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  • Reviewed by Dr Kristina Routh, Freelance Health Editor, Bupa Health Content Team, May 2019
    Expert reviewer Dr Tim Cripps, Consultant Cardiologist
    Next review due May 2022