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Interaction scenario

Potassium-raising medicine combinations: ACE inhibitors, spironolactone and more

Potassium keeps the heart rhythm steady, so both too little and too much are dangerous. Several common medicines tend to raise it, and combining them, or adding a salt substitute, can tip some people into high potassium. This scenario guide lists the combinations named by the NHS and the symptoms to watch for.

Last checked: 2026-10-03

Key facts

At a glance.

  • Ramipril list

    The NHS ramipril page lists spironolactone, triamterene, amiloride and potassium, along with trimethoprim and heparin, among medicines to tell the doctor about.

  • Salt substitutes

    The NHS says salt substitutes such as Lo-Salt contain high potassium and should be avoided with ramipril and spironolactone.

  • Foods too

    The NHS spironolactone page says bananas and avocados as well as salt substitutes can raise potassium further.

  • Symptoms

    The NHS lists muscle weakness, tiredness, numbness and irregular heartbeat as symptoms of high potassium needing urgent attention.

  • Blood tests guide care

    Potassium is found by a blood test, so ask when your monitoring is due if you take several relevant medicines.

Why potassium needs balance

Potassium is controlled mainly by the kidneys and by a hormone system that ACE inhibitors, ARBs and spironolactone act on. When those medicines reduce the kidney's ability to get rid of potassium, levels can climb. In the opposite direction, some water tablets and vomiting or diarrhoea can lower potassium, which matters for heart rhythm, as our QT guide describes.

High potassium may cause no symptoms until it is quite high, so blood tests are the main safeguard for people on relevant medicines.

The medicine groups that raise potassium

The NHS ramipril page lists spironolactone, triamterene, amiloride and potassium among the medicines that need discussion with a doctor, together with trimethoprim and heparin. The NHS spironolactone page names digoxin, eplerenone, NSAIDs such as ibuprofen, aspirin and diclofenac, and potassium supplements among interacting medicines.

Our guide on ACE inhibitors and potassium covers the best-known pairing in detail. The point of this page is that the risks can stack: an ACE inhibitor plus spironolactone plus a short course of trimethoprim for a urine infection is a combination where a pharmacist or prescriber will think carefully.

  • ACE inhibitors such as ramipril, and related ARBs.

  • Potassium-sparing diuretics: spironolactone, amiloride, triamterene, eplerenone.

  • Trimethoprim and heparin.

  • NSAIDs.

  • Potassium supplements.

Salt substitutes and foods

The NHS ramipril page says to avoid salt substitutes such as Lo-Salt because they contain high levels of potassium, and the spironolactone page says foods such as bananas and avocados, and salt substitutes, can raise potassium further. It advises consulting a doctor or dietitian about dietary restrictions.

Low-sodium products sold as heart-healthy are an easy trap for someone advised to cut salt. Read labels and look for potassium chloride, and ask the pharmacist before using them.

Antibiotics and short courses

Trimethoprim is a common antibiotic for urinary infections, and the NHS ramipril page names it among medicines to check. Although the trimethoprim page we retrieved focuses on other interactions such as anticoagulants, digoxin and methotrexate, the ramipril warning means anyone on an ACE inhibitor should flag it when offered trimethoprim.

A pharmacist can often suggest checking a blood test after a course if several risk factors are present, particularly in older adults or those with kidney disease.

Symptoms and urgent help

The NHS spironolactone page lists muscle weakness, tiredness, numbness and an irregular heartbeat as symptoms of high potassium. Call NHS 111 for these, and call 999 for chest pain, collapse or a very slow or erratic pulse with faintness.

Do not take extra potassium supplements without a blood result. If you are vomiting or have diarrhoea while taking an ACE inhibitor or diuretic, ask for advice about whether to pause the tablets.

Monitoring and review

People starting ACE inhibitors, ARBs or spironolactone usually have kidney function and potassium checked soon after starting and after dose changes. When a new interacting medicine is added, ask whether an extra test is needed. Keep a list of all your medicines in one place so any new prescriber sees the full picture.

Frequently asked

Questions people ask.

Quick, plain-English answers to the questions we hear most.

  • Which medicines raise potassium?

    The NHS names spironolactone, triamterene, amiloride, potassium supplements and others alongside ramipril, including trimethoprim and heparin.

  • Are salt substitutes safe on an ACE inhibitor?

    The NHS says to avoid salt substitutes such as Lo-Salt with ramipril because they contain high levels of potassium.

  • Do bananas matter?

    The NHS spironolactone page says bananas and avocados can raise potassium further, so ask a dietitian or doctor how much is appropriate for you.

  • What are the symptoms of high potassium?

    The NHS lists muscle weakness, tiredness, numbness and irregular heartbeat. Seek urgent medical help for these.

  • Can trimethoprim raise potassium?

    The NHS ramipril page lists trimethoprim as a medicine to tell the doctor about, so mention your ACE inhibitor when offered it.

  • Do NSAIDs raise potassium?

    The NHS spironolactone page lists NSAIDs among interacting medicines. They can also affect the kidneys, as our triple whammy guide explains.

  • How do I know my potassium level?

    It is measured by a blood test. Ask your GP how often it should be checked while you take your medicines.

  • Should I stop my tablets if I think my potassium is high?

    Do not stop without advice. Seek urgent help if you have symptoms, and speak to the GP about a blood test.

  • Does low potassium also matter?

    Yes. The NHS says very low potassium can cause acquired long QT, so both extremes need attention.

Where this comes from

Sources and checking.

This guide is for information, not medical advice.

Your GP or consultant knows your history and can tell you which parts apply to you. If your symptoms are severe, rapidly worsening, or come with red-flag features, seek urgent medical care. Figures and availability change, so treat them as a guide and confirm with the provider.

Published 2026-10-03, next review 2027-10-03.

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