Aldosterone-to-renin ratio test: what it is, who gets it and how to prepare

The aldosterone-to-renin ratio (ARR) test compares two hormones that work as a pair: aldosterone, made by your adrenal glands, and renin, made by your kidneys. Together they help control blood pressure and the balance of sodium and potassium in your blood. The test is mostly used when a clinician wants to know whether an adrenal hormone is contributing to high blood pressure.

If you came here from a diagram of the “renin-angiotensin-aldosterone system”, the plain-language version is below, followed by what the test is, how to prepare and what to check before you order.

Aldosterone-to-renin ratio

Sold as an aldosterone-to-renin ratio test. Check what it reports on the seller’s page before you order.

$149

The seller's product page describes an aldosterone blood test and does not say renin is included. Check that before you order. Never stop or change a blood pressure medicine for a test unless your prescriber tells you to.

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How the renin and aldosterone system works

MedlinePlus says your kidneys release renin when your blood pressure or sodium decreases or your potassium increases. Renin controls the production of aldosterone, which your adrenal glands make. Aldosterone helps keep blood pressure stable by balancing sodium and potassium. Usually, if renin goes up or down, aldosterone does the same.

A medical-education review adds the middle step. Renin is an enzyme that converts a protein called angiotensinogen to angiotensin I, which is converted to angiotensin II. Angiotensin II prompts the outer layer of the adrenal glands to release aldosterone, which increases sodium reabsorption in the kidneys. Water follows the sodium, and blood pressure rises.

In order:

1. Blood pressure or sodium falls, or potassium rises.
2. The kidneys release renin.
3. Renin starts the conversion to angiotensin I, then angiotensin II.
4. Angiotensin II tells the adrenal glands to release aldosterone.
5. Aldosterone makes the kidneys hold on to sodium and remove potassium, which raises blood pressure.
6. When blood pressure returns to normal, aldosterone levels decrease.

MedlinePlus says the levels of both hormones are highest in the morning and change through the day.

What the ratio test is and why it is done

MedlinePlus says an aldosterone test is commonly combined with a renin test, which is called an aldosterone-renin ratio test. It is mainly used to help diagnose two kinds of adrenal gland disorders. One is primary aldosteronism (also called Conn syndrome), usually caused by a benign tumor on an adrenal gland that makes extra aldosterone. The other is adrenal insufficiency, including Addison disease.

A 2022 paper says the ARR is the currently recommended screening test for primary aldosteronism, and that primary aldosteronism affects 5 to 10 percent of primary care patients with high blood pressure. “Screening” matters. A positive ARR leads to confirmatory testing, not to a diagnosis. The paper says people with an abnormally elevated ARR should be referred to a specialist for that.

The test can also help find the reason for abnormal sodium or potassium results and the cause of a sudden drop in blood pressure on standing, according to MedlinePlus.

Who gets tested

MedlinePlus says you may need this test if you have signs or symptoms of high or low aldosterone, or high blood pressure that:

• happens with low potassium,
• doesn’t improve with the usual blood pressure medicines, or
• develops at a young age.

Symptoms linked to too much aldosterone include high blood pressure, muscle weakness or cramps, fatigue, headache, thirst and frequent urination. Symptoms linked to too little include low blood pressure, fatigue, muscle weakness, loss of appetite and weight loss. All of these have many other causes.

How to prepare

This is a test where preparation changes the result. MedlinePlus gives these points:

• Body position. Aldosterone changes depending on whether you are standing or lying down. You may be asked to lie down or stand for a set time before the sample, or be tested in both positions.
• Medicines. Some medicines can affect results, including birth control pills, blood pressure medicines and diuretics (water pills). Your provider may give instructions about certain ones, including some over-the-counter medicines. Don’t stop or change any prescribed medicine unless your provider tells you to.
• Salt. You may be asked to limit salt for about two weeks before the test. Your provider explains how.
• Natural black licorice. Avoid it for at least two weeks before the test, because it can affect results. Most licorice products in the United States don’t contain natural licorice, so check the label.

A 2022 paper says common blood pressure medicines can influence the ratio, and that careful patient preparation, including adjusting existing medicines, is needed to avoid errors. That adjustment is the prescriber’s job, not something to do alone for an online order.

Why ratio cut-offs and sample handling vary

Two things make the ARR less tidy than a single number suggests.

• Cut-offs depend on the lab. The 2022 paper says the ARR threshold considered abnormal depends heavily on the assays used to measure aldosterone and renin, and that thresholds vary widely between studies. There is no one ratio to compare against, so this page doesn’t give one. Your clinician uses the method and cut-off of the lab that ran your sample.
• Renin is sensitive to storage. A 2024 paper in the Journal of Clinical Endocrinology and Metabolism says storing renin plasma at temperatures between about +4 and -5 degrees Celsius, and also at -20, can cause falsely high renin results, which can distort the ratio. This is a laboratory matter. It is one reason repeat results can differ.

A medical-education review says renin interpretation depends on salt intake, posture, time of day and medicines. Your lab’s own ranges apply.

What the seller’s page says

The seller’s page for this test carries “aldosterone-to-renin ratio” in its title. Its body text describes an aldosterone blood test, says the test measures the concentration of aldosterone in your blood, and doesn’t mention renin or a ratio. It also doesn’t give instructions about time of day, posture, salt or medicines. It says fasting is not required and that you can eat and drink normally unless your doctor has given you other instructions. The sample is a simple blood draw, and results are shown in your account within one to three business days. The page presents the test for hard-to-control high blood pressure and low potassium.

What to do with that:

1. Check what the order reports. A ratio needs both numbers. If a clinician asked for an ARR, confirm that your order includes renin, not only aldosterone. If the page doesn’t say, ask the seller before you buy.
2. Ask your clinician about preparation. Position, salt, licorice and medicines all matter, and the seller’s page doesn’t cover them.
3. Compare sellers. Prices for the same type of test vary widely, and it is worth comparing. See cost and where to buy.

What the test can’t show

• It can’t diagnose primary aldosteronism on its own. It is a screening step. Confirmatory testing follows an abnormal screen.
• It isn’t a cortisol test. Aldosterone and cortisol are both adrenal hormones, but they are controlled differently. For cortisol, see the cortisol test guide.
• It can’t explain high blood pressure by itself. MedlinePlus says to understand your results, your provider considers aldosterone along with other tests. See cortisol and blood pressure.
• It isn’t a test for “adrenal fatigue”. That is not a recognized diagnosis. See adrenal tests.

Blood sodium and potassium are often looked at alongside this test. See sodium and potassium in adrenal work-ups.

When to see a clinician

Talk to your clinician if you have high blood pressure that isn’t responding to treatment, high blood pressure with low potassium, or high blood pressure that began at a young age. Take your medicine list with you. If a clinician has ordered an ARR, ask exactly how to prepare, and don’t stop or adjust a blood pressure medicine without their instruction.

If you have repeated vomiting, severe weakness or fainting, don’t wait for a test. Call 911 or go to the nearest emergency room. See adrenal crisis.

Questions people ask

Is aldosterone made by the adrenal glands?

Yes. MedlinePlus says aldosterone is a hormone made by the adrenal glands. Renin is made by the kidneys.

What is the difference between renin and aldosterone?

Renin comes from the kidneys and acts first. Aldosterone comes from the adrenal glands and acts on the kidneys in response. See the steps above.

Do I need to fast for an ARR test?

The seller’s page says fasting is not required. MedlinePlus says to follow the instructions your provider gives you, which can include body position, salt and medicines.

Keep reading

• Adrenal tests

  Every adrenal blood test and what it answers.

• Cortisol and blood pressure

  How adrenal hormones relate to blood pressure.

• Sodium and potassium

  Electrolytes in an adrenal work-up.

• ACTH blood test

  The pituitary signal to the adrenal glands.