High Aldosterone Renin Ratio: What Does a Positive Screen Mean?

A high aldosterone renin ratio (ARR) means that aldosterone was high relative to renin in your blood sample. It is the usual screening test for primary aldosteronism, a condition in which the adrenal glands make too much aldosterone. A positive screen means further assessment is needed; it does not by itself confirm the diagnosis.

This guide is for adults with high blood pressure who have an ARR result. It explains the questions around the result. It cannot interpret your numbers, because cut-offs depend on the laboratory method and units used.

Primary aldosteronism can cause low potassium. MedlinePlus notes that a large fall in potassium can cause dangerous heart rhythm problems, and severe muscle weakness or paralysis in serious cases.

• Call local emergency services for chest pain that does not go away, fainting, or signs of a stroke such as face drooping, arm weakness or slurred speech.
• Seek same-day advice for new marked muscle weakness, a racing or irregular heartbeat, or lightheadedness, especially if you have been told your potassium is low.
• Contact your clinician promptly if you take a water tablet (diuretic) and develop symptoms of low potassium, or if you have had heavy vomiting or diarrhoea.

Aldosterone is a hormone that helps balance sodium and potassium and control blood pressure. Renin is part of the system that normally regulates it. In primary aldosteronism, aldosterone is made regardless of renin, so renin is pushed low while aldosterone stays relatively high. That is why the two are measured together.

The Endocrine Society's patient guide states that primary aldosteronism affects 5 to 14 percent of people with high blood pressure and is the most common hormonal cause of it. Most people with it have no specific symptoms. Its 2025 guideline suggests screening everyone with high blood pressure, while recognising that local resources vary.

Screening matters because the condition is linked to a higher risk of heart disease, stroke, atrial fibrillation and kidney damage, and specific treatment can reduce these risks.

Many blood pressure medicines change renin or aldosterone, so the clinician reading your result needs to know exactly what you take. The 2025 guideline describes these effects.

• Medicines that can make a screen falsely negative: aldosterone-blocking medicines (mineralocorticoid receptor antagonists), other diuretics, ACE inhibitors and angiotensin receptor blockers.
• Medicines that can make a screen falsely positive: beta blockers and some centrally acting blood pressure medicines.
• Natural black liquorice can also affect results, according to MedlinePlus.
• Some services test without changing medicines; others adjust them first. Only change or stop a medicine on your clinician's instructions, because stopping blood pressure treatment can be unsafe.

Low potassium can falsely lower aldosterone and hide the condition. The guideline recommends measuring potassium at the same time and, if a screen is negative while potassium is low, correcting potassium and repeating the test. Low potassium supports suspicion of primary aldosteronism, but a normal level does not rule it out. Our guide on low potassium blood tests covers the result itself.

Sampling conditions matter too. The guideline recommends a morning sample taken while seated, and advises against cutting down on salt in the days before. MedlinePlus notes that aldosterone changes with posture, and some services give their own instructions about salt, so follow the preparation advice from the service doing your test.

A ratio is not the whole story. The American Family Physician review notes that the ratio can look exaggerated when renin is very low, so clinicians also look at the actual aldosterone and renin values, not just the calculated figure. The guideline also asks laboratories and clinicians to use local cut-offs and to consider how likely the condition was before the test.

The next step depends on how clear the result is, your potassium, your blood pressure and whether surgery would be an option for you. Possible next steps include:

• Repeating the screen after a medicine review if a medicine may have affected the result.
• A confirmatory (suppression) test, which checks whether aldosterone stays high when it should fall. Examples include a saline infusion test, an oral salt-loading test and a captopril challenge. The 2025 guideline no longer suggests one for everyone, mainly when the result would change a surgical decision.
• Adrenal CT imaging. A scan may show a nodule, but it cannot reliably tell whether the nodule is making the hormone.
• Adrenal vein sampling, done in specialist centres, for people considering surgery, to find out whether one or both glands are the source.
• Referral to an endocrinologist.

If the condition is confirmed, the Endocrine Society describes two main approaches. When one adrenal gland is the source, removing it with keyhole surgery may cure the condition. When both glands are involved, or surgery is not chosen, aldosterone-blocking medicines are used, with follow-up blood tests and blood pressure checks.

If a nodule was found on a scan for another reason, our guide on incidental adrenal nodules explains why hormone testing is part of that assessment. Accurate blood pressure readings also matter during follow-up; see our guide on readings that differ at home and in the clinic.

Bring your report and a full list of your medicines and supplements.

• What were my aldosterone, renin and potassium values, and what cut-off does this laboratory use?
• Could any of my medicines have affected the result, and do I need a repeat test?
• Was my potassium low, and does it need treating before any repeat test?
• Do I need a confirmatory test, a scan or adrenal vein sampling, and why?
• Should I be referred to an endocrinologist, and how long is the wait?
• If this is confirmed, how might treatment change my current medicines?

On SameCase, patients and verified doctors share de-identified cases. Seeing how other people's positive ARR screens were followed up, such as which were repeated after a medicine review or went on to adrenal vein sampling, can help you prepare questions for your own appointment.

Other cases cannot tell you whether you have primary aldosteronism. We do not diagnose, and your clinicians decide which tests and treatment suit you.