Aldosterone / Renin Activity Ratio (ARR)
A calculated ratio of aldosterone to plasma renin activity. Clinicians use it as a first step when looking into primary aldosteronism in people with high blood pressure.
AI-drafted. Awaiting verificationAlso called ARR, A/RA, PAC/PRALOINC 30894-0
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What it is
Aldosterone and renin normally move in step: when renin falls, aldosterone should fall too. The ratio compares the two. A high ratio means aldosterone is high compared with renin, which can happen when the adrenal glands make aldosterone on their own. Labs get the ratio by dividing your aldosterone (in ng/dL) by your plasma renin activity (in ng/mL per hour), so it depends on both measurements.
Why it matters
The ratio is a first-step test, not a diagnosis. A result above the cut point is a reason for more testing. The Endocrine Society's 2025 guideline suggests testing aldosterone and renin in everyone with high blood pressure, because primary aldosteronism is often missed. The ratio can mislead, though. Medicines, potassium, salt intake and age can all push it up or down, so both false alarms and missed cases happen, and your own lab's cut point matters.
If it’s low
A low ratio is usually not a concern. It often reflects a high renin level, which low salt intake, dehydration, water pills, ACE inhibitors and angiotensin receptor blockers can cause. It can also be falsely reassuring. Low potassium or some medicines can hide a high ratio. A clinician may repeat the test on another day if there is a strong reason to suspect primary aldosteronism.
Common causes
- ACE inhibitors or angiotensin receptor blockers
- Water pills (diuretics) or aldosterone-blocking medicines
- Low potassium
- Low salt intake or dehydration
- Pregnancy
- Narrowed kidney arteries or very high blood pressure
What can help
- Ask whether your medicines or your potassium level could have affected the result
- Ask whether the test should be repeated if your clinician still has concerns
If it’s high
A high ratio means aldosterone is high compared with renin. Several everyday things can push it up, such as beta-blockers, clonidine, anti-inflammatory pain medicines (NSAIDs), older age, kidney problems and a high-salt diet. A high ratio is a reason for more testing, not a diagnosis. If aldosterone is also high and renin is low, a clinician may suggest confirmation tests.
Common causes
- Beta-blockers, clonidine or NSAIDs
- Age 65 or older
- Reduced kidney function
- A high-salt diet
- A very low renin reading
- Primary aldosteronism, where the adrenal glands make too much aldosterone on their own
What can help
- Ask whether your medicines could have changed the ratio, and don't stop any on your own
- Ask whether your potassium was normal on the day of the test
- Ask whether a repeat test or a confirmation test makes sense
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: 0–30 ng/dL per ng/mL/h. Source: Labcorp, ARUP Laboratories, ARUP Consult.
- Adults (this one applies)0–30 ng/dL per ng/mL/h
Sources: Labcorp, ARUP Laboratories, ARUP Consult
Endocrine Society 2025 first-step cut point, aldosterone by immunoassay (a positive result also needs aldosterone of 10 ng/dL or more and PRA of 1 ng/mL/h or less)
- 20 or lowerbelow 20 ng/dL per ng/mL/h
- Above 2020 and above ng/dL per ng/mL/h
Endocrine Society 2025 first-step cut point, aldosterone by LC-MS/MS (a positive result also needs aldosterone of 7.5 ng/dL or more and PRA of 1 ng/mL/h or less)
- 15 or lowerbelow 15 ng/dL per ng/mL/h
- Above 1515 and above ng/dL per ng/mL/h
What can affect your result
- Medicines that raise or lower aldosterone or renin
- Potassium level: low potassium can hide a high ratio
- Salt intake: restriction can hide a high ratio, and extra salt can inflate it
- Age, kidney function and pregnancy
- Posture, time of day and sample handling (the renin tube should not be chilled)
- The assay used for aldosterone (immunoassay or LC-MS/MS)
- Medicines change the ratio. Beta-blockers, clonidine and NSAID pain relievers can raise it (a false positive). ACE inhibitors, angiotensin receptor blockers, water pills, aldosterone-blocking medicines and dihydropyridine calcium blockers can lower it (a false negative). Never stop a medicine on your own: your clinician decides whether to test as you are or to adjust some medicines first.
- Low potassium can lower the ratio, so potassium is measured with it and corrected before a negative result is trusted.
- A low-salt diet can hide a high ratio, and a high-salt diet can inflate it.
- Age 65 or older and reduced kidney function tend to raise the ratio. Pregnancy tends to lower it.
- Chilling the renin tube can activate prorenin and falsely raise renin, which lowers the ratio, so labs ask for room-temperature handling and prompt freezing of the plasma.
- Estrogen-containing birth control or hormone therapy can distort ratios built on direct renin, so ARUP prefers this renin-activity version for menstruating women and people taking estrogen.
Mid-morning, after being up (sitting, standing or walking) for at least 2 hours and then seated for 5 to 15 minutes (Labcorp). The Endocrine Society (2025) says morning, seated, without dietary salt restriction in the days before. Shows the moment of the draw. Medicines that interfere with the test can take 2 to 4 weeks to clear.
When to talk to a clinician
Contact the clinician who ordered the test if your lab flagged the result. Seek urgent care for severe muscle weakness, fainting, a racing or uneven heartbeat or confusion. If your blood pressure is very high and you have chest pain, trouble breathing, vision changes or a severe headache, call 911 or your local emergency number.
Questions you could ask
- Which renin test did my lab use, and does my lab use its own cut point?
- Do my medicines, my potassium level or my age change how to read this ratio?
- Is it worth repeating, or should we look at aldosterone and renin separately?
- Could my medicines or a low potassium level have hidden a high ratio?
Questions people ask
Why does my lab's range differ from the guideline's cut point?
A lab range describes where results from a group of people fall. A guideline cut point is chosen to balance missed cases against false alarms, and a positive first-step result also needs aldosterone to be high enough and renin to be low. The Endocrine Society says to use your own lab's cut points where possible. Neither one is a diagnosis.
Should I stop my blood pressure medicine before this test?
Please don't stop any medicine on your own. Some medicines change aldosterone and renin, and your clinician decides whether to test as you are, adjust a few medicines for a short time, or repeat the test later. The Endocrine Society describes all three options.
Why does the ratio have units?
The ratio divides aldosterone in ng/dL by renin activity in ng/mL per hour, so it keeps both units, even though many reports print only a number. A ratio made with a different renin test (direct renin) or different units is on a different scale, so cut points don't carry over.
Show the science and sources
Units
- 1 ng/dL per ng/mL/h = 1 ng/dL per ng/mL/h
- 1 ng/dL per ng/mL/h = 27.75 pmol/L per ng/mL/h
For clinicians and researchers
ARR = aldosterone (ng/dL) ÷ plasma renin activity (ng/mL/h). The Endocrine Society's 2025 guideline suggests measuring aldosterone and renin (with potassium) in all people with hypertension. In most circumstances a positive screen needs low renin (PRA 1 ng/mL/h or less) and aldosterone of 10 ng/dL or more by immunoassay or 7.5 ng/dL or more by LC-MS/MS, with an ARR above 20 ng/dL per ng/mL/h (immunoassay) or above 15 (LC-MS/MS); in pmol/L per ng/mL/h these are above 555 and above 416. Its Table 5 also gives cut points for PRA in pmol/L/min or ng/L/s and for direct renin. The guideline says to rely on local laboratory cut points where possible, because every cut point trades false positives against false negatives. Lab-printed intervals differ from these cut points: Labcorp (LC-MS/MS aldosterone with PRA) prints 0.0 to 30.0 and ARUP prints 20 or less, while the ARUP Consult fact sheet (updated January 2026) still lists 25. The ratio is a detection test. False positives are described with beta-blockers, central alpha-2 agonists, NSAIDs, age over 65, renal impairment and sodium loading, and false negatives with ACE inhibitors, ARBs, diuretics, MRAs, dihydropyridine calcium blockers, hypokalemia, sodium restriction, pregnancy and renovascular or malignant hypertension. A PRA-based ratio is preferred over a direct-renin ratio in menstruating or estrogen-treated patients. Conversion: ARR in pmol/L per ng/mL/h × 0.03604 = ARR in ng/dL per ng/mL/h.
LOINC 30894-0 (primary), 103560-9. Specimen: calculated.
Sources
- Aldosterone:Renin Ratio (test 004354), Labcorp
- Aldosterone/Renin Activity Ratio (test 0070073), ARUP Laboratories
- Aldosterone-Renin Ratio (Test Fact Sheet), ARUP Consult (2026)
- Primary Aldosteronism: An Endocrine Society Clinical Practice Guideline, Journal of Clinical Endocrinology & Metabolism (2025)
- Aldosterone (PubChem CID 5839), NCBI PubChem
AI-drafted. Awaiting verification. Last reviewed 2026-10-03. How we build and check these pages.