Also Known As
Aldosterone and Plasma Renin Activity
PRA
Formal Name
Aldosterone, serum; Aldosterone, urine; Renin
This article was last reviewed on
This article waslast modified on
25 May 2018.
At a Glance
Why Get Tested?

To see if your aldosterone or renin levels are abnormal; to detect hyperaldosteronism (overproduction of aldosterone) or hypoaldosteronism (underproduction of aldosterone)

When To Get Tested?

If your doctor finds an electrolyte imbalance or you develop symptoms of hyperaldosteronism, such as high blood pressure or muscle weakness

Sample Required?

A blood sample taken from a vein in your arm or a 24-hour urine sample

Test Preparation Needed?

You may be asked to adhere to an unrestricted salt diet prior to the test or to temporarily discontinue one or more medications. Please follow any instructions you are given, as this is important to ensure the validity of test results.

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you will be able to access your results online.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, gender, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

Aldosterone is a hormone which regulates the retention of sodium (salt) and water by the kidney and also regulates the removal of potassium. It plays an important role in the control of blood pressure.
Aldosterone is produced by the adrenal glands which are located at the top of each kidney. Its production is stimulated by a complex process that includes several other "hormones", the most important of these being renin and angiotensin II. Renin, produced by the kidney, stimulates production of angiotensin II in the bloodstream. Angiotensin II then regulates the release of aldosterone. Normally when renin increases, aldosterone increases; when renin is low, aldosterone decreases.

How is the sample collected for testing?

A blood sample required for measurement of plasma aldosterone and/or renin levels is taken by needle from a vein in the arm. One sample, collected in the morning, usually arround 9am, is usually sufficient for the initial investigation of aldosterone and renin disorders. However, because the levels of aldosterone and renin change when a person moves from lying down to standing up, your doctor may collect one sample whilst you are lying down and another after you have been upright for a few hours.

Is any test preparation needed to ensure the quality of the sample?

You may be asked to adhere to an unrestricted salt diet prior to the test or to temporarily discontinue one or more medications. Please follow any instructions you are given, as this is important to ensure the validity of test results.

Accordion Title
Common Questions
  • How is it used?

    The ratio between these two hormones compared with the aldosterone concentration within the bloodstream can be a very helpful investigation. These results together with the cortisol concentration, can give important information about some of the hormone disorders associated with the adrenals and kidneys indicated in the table below

    Disease Aldosterone Renin Cortisol
    Primary hyperaldosteronism (Conn’s syndrome) High Low Normal
    Secondary hyperaldosteronism High High Normal
    Cushing’s syndrome Low-normal Low High
    Adrenal insufficiency (Addison's disease) Low High Low

    Primary hyperaldosteronism (Conn's syndrome) is caused by the overproduction of aldosterone in the adrenal glands, usually by a benign tumour of one of the glands. The high aldosterone level increases reabsorption of sodium (salt) and water and the loss of potassium by the kidneys, resulting in high blood pressure (also called 'hypertension'). Also muscle weakness can occur if potassium levels are very low.

    Secondary hyperaldosteronism is more common and can occur as a result of anything that decreases blood flow to the kidneys, decreases blood pressure, or lowers sodium levels within the bloodstream. The most important cause is narrowing of the blood vessels that supply the kidney, called 'renal artery stenosis'. This stimulates production of renin and aldosterone, which in turn leads to raised blood pressure. Sometimes, to see if only one kidney is affected, a catheter is inserted through the groin and blood is collected directly from the veins draining the kidney. Renin is then measured in these blood samples. If the value is significantly higher in one side, this indicates the site of the narrow artery. Other causes of secondary hyperaldosteronism include congestive heart failure, cirrhosis of the liver, kidney disease, and pre-eclampsia in pregnancy.

    Hypoaldosteronism (i.e. a lack of aldosterone) usually occurs as part of adrenal insufficiency (Addison's disease). It causes dehydration, low blood pressure, high potassium (hyperkalaemia) and low sodium (hyponatraemia) in the blood.

  • When is it requested?

    Aldosterone and renin tests are usually requested together. High blood pressure together with a low potassium concentration within the bloodstream usually leads the doctor to request these two tests. Aldosterone levels are sometimes used in people suspected of having poor adrenal function. Some doctors use aldosterone and renin levels to point to the likely treatments that will be effective in persons with high blood pressure.

  • What does the test result mean?

    The changes in plasma aldosterone, cortisol, and renin are summarised in the table earlier. High levels of serum and urine aldosterone, along with a low plasma renin, indicate primary hyperaldosteronism (Conn's syndrome). Secondary hyperaldosteronism, on the other hand, is indicated by an increase in both aldosterone and renin.

    A low aldosterone concentration is usually part of adrenal insufficiency (Addison's disease). In infants with a condition called congenital adrenal hyperplasia (CAH), the infant lacks an enzyme needed to make cortisol; in some cases, this also decreases production of aldosterone which is a rare cause of low aldosterone.

  • Is there anything else I should know?

    The amount of salt in the diet and medicines, such as over-the-counter pain relievers of the non-steroid class (such as Nurofen and Hedexl), diuretics (water pills), beta blockers, steroids, angiotensin-converting enzyme (ACE) inhibitors, and oral contraceptives can affect the test results. Many of these drugs are used to treat high blood pressure. Your doctor will tell you if you should change the amount of sodium (salt) you ingest in your diet, your use of diuretics or other medications, or your exercise routine before aldosterone and renin are tested.

    Aldosterone concentrations within the blood can fall to very low levels with severe illness, so testing should be done after recovery.

  • Are there any other precautions I should take before the test?

    Liquorice can mimic aldosterone properties and should be avoided for at least two weeks before the test. This refers only to the actual products of the liquorice plant (hard liquorice); most soft liquorice and other forms of liquorice confectionary sold in the UK do not actually contain the plant extract. Check the packages label if you are not certain, or bring a package with you to ask your doctor. Stress and strenuous exercise may also alter the results.

  • If my posture is important in the outcome of the results, how can I control it?

    This is not necessary if a blood sample is taken for both renin and aldosterone measurement, as the ratio between the two hormones will be calculated (aldosterone/renin).

  • Are there any other conditions associated with abnormal aldosterone levels?

    Prolonged use of steroids, a diet high in salt, some blood pressure medications, and Addison’s disease can lower aldosterone levels.