Version July 2025
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What is an aldosterone test? —
This test measures the amount of aldosterone in the body. Aldosterone is a hormone that helps control the amount of salt and fluid in the body. It is made in the "adrenal glands," which are small organs located on top of each kidney.
Aldosterone is important for keeping blood pressure in the right range. Having too much or too little aldosterone can lead to health problems.
The aldosterone level can be measured using a sample of blood or urine. For the blood test, it is often measured along with another hormone called "renin."
Why might I get an aldosterone test? —
Your doctor might want you to have an aldosterone blood test:
●To help find the cause of high or low blood pressure
●If you have symptoms of "adrenal insufficiency" – This is a disorder in which the adrenal glands can't make enough aldosterone or other hormones like cortisol.
●If you have a growth on the adrenal gland – Sometimes, these growths can make hormones like aldosterone.
●To learn more if you have abnormal levels of sodium or potassium – Aldosterone helps balance the levels of these substances in the body.
The urine test is most often done if a blood test shows a high aldosterone level. Testing the urine can confirm this.
How do I prepare for an aldosterone test? —
You need to give a sample of blood or urine. Which sample you give depends on what problems you are being tested for.
The sample is then tested in a lab to measure the amount of aldosterone. Your doctor or nurse will tell you which test you are having, and exactly what you need to do to prepare for it. For example, they will tell you if you need to change your diet before the test.
You might also be asked to stop taking certain medicines a few weeks before the test.
What happens during an aldosterone test? —
It depends on whether you are testing a sample of blood or urine.
If your blood is being tested:
●You need to get a "blood draw." Your doctor or nurse will tell you where to go for this.
●It might help to wear a short-sleeve shirt to your blood draw appointment. This makes it easier for the person drawing your blood to get to your arm.
●A needle is used to take a small amount of blood from your arm (figure 1). Collecting the blood only takes a few minutes. The blood is then tested in a lab.
●Make sure to tell the person who takes your blood:
•If you take "blood thinner" medicines or have a bleeding problem – They will make sure your bleeding is under control before you leave.
•If you have a latex allergy – Some of the supplies used for blood draws might contain latex.
•If you have a preferred arm to use
●Most of the time, getting blood taken does not cause problems. You might have a little soreness or bruising where the needle went in.
If your urine is being tested:
●You might be asked to increase your salt intake for 3 days. You might do this through your diet, or with salt pills. This is to see how increased salt in your body affects the level of aldosterone in your urine.
●On the third day, you will do a "24-hour urine collection." This is when you collect all the urine you make in a 24-hour period. Your doctor or nurse will give you instructions for exactly how to do this. Usually, you do it at home. You might need to do it more than once so your doctor can compare your results.
What do my results mean? —
Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.
If your aldosterone test shows any abnormal results, your doctor or nurse will talk to you about what to do next. They might need to do more tests to figure out the cause.
If you do have a health problem, your doctor will work with you to come up with a treatment plan.
Patient education: High blood pressure in adults (The Basics)
Patient education: High blood pressure in children (The Basics)
Patient education: Addison disease (The Basics)
Patient education: Adrenal crisis (The Basics)
Patient education: 24-hour urine collection (The Basics)
Patient education: High blood pressure in adults (Beyond the Basics)
Patient education: High blood pressure in children (Beyond the Basics)
Patient education: Adrenal insufficiency (Beyond the Basics)
Patient education: Collection of a 24-hour urine specimen (Beyond the Basics)
