Blood test
Aldosterone and Renin Test
This blood test measures the hormones aldosterone and renin, which control salt, water and blood pressure, mainly to investigate certain causes of high blood pressure.
Quick answer
Aldosterone and Renin Test: what it is and what the results mean
Aldosterone and renin are hormones that regulate sodium, potassium and blood pressure. Measuring them, often as a ratio (the aldosterone-to-renin ratio), helps identify hormone-driven causes of high blood pressure.
- Why it is done: It is used to investigate high blood pressure that is difficult to control, occurs at a young age, or is associated with low potassium, to look for conditions such as primary aldosteronism (Conn’s syndrome).
- Understanding results: A high aldosterone with a suppressed renin suggests the adrenal glands are producing too much aldosterone.
What it is
Aldosterone and renin are hormones that regulate sodium, potassium and blood pressure. Measuring them, often as a ratio (the aldosterone-to-renin ratio), helps identify hormone-driven causes of high blood pressure.
Why it is done
It is used to investigate high blood pressure that is difficult to control, occurs at a young age, or is associated with low potassium, to look for conditions such as primary aldosteronism (Conn’s syndrome).
What to expect
It is a blood test from a vein in the arm, but preparation matters: certain blood pressure medicines may need to be changed beforehand, salt intake and timing can affect results, and posture before the test is sometimes controlled.
Understanding the results
A high aldosterone with a suppressed renin suggests the adrenal glands are producing too much aldosterone. Abnormal results usually lead to confirmatory tests and imaging under specialist care.
Good to know
Risks and limitations
The blood test is safe, but results are easily affected by medicines, salt intake, potassium levels and posture, so careful preparation and specialist interpretation are essential.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Aldosterone and Renin Test: frequently asked questions
Why might I need to change my blood pressure tablets before this test?
Some blood pressure medicines interfere with aldosterone and renin levels and can make the result misleading, so your doctor may adjust them beforehand under supervision.
What condition is this test looking for?
It is mainly used to detect primary aldosteronism (Conn’s syndrome), where the adrenal glands make too much aldosterone, causing high blood pressure and sometimes low potassium.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- Association for Laboratory Medicine / relevant professional body
Building patient-education content for tests or procedures?
We create clear, accurate, referenced medical explainers and decision aids for teams.