Hypertension with an endocrine cause

Requires a medical indication

Blood test to investigate a possible endocrine cause of hypertension: primary aldosteronism. It includes aldosterone, renin, the aldosterone/renin ratio, sodium, potassium and kidney function. The preparation should be coordinated by the doctor who manages your blood pressure, because several antihypertensive medicines and low potassium can alter the result.

Requires a medical prescription

Results in 1-2 working days

Includes: Aldosterone · Renin · Aldosterone/renin ratio · Sodium and potassium · Creatinine and eGFR. See what each one measures

This test can only be interpreted properly if a doctor has prepared the conditions beforehand: some medicines have to be stopped weeks in advance, potassium has to be corrected, and the sample has to be taken in a specific posture and at a specific time. Without that, the result means nothing. Talk to your doctor before ordering it.

What it is for

It is used to look for primary aldosteronism, a cause of hypertension in which the adrenal glands produce aldosterone inappropriately. Identifying it matters because it requires a specific investigation and can change blood pressure treatment.

This profile carries out the initial screening. If the ratio is abnormal, the diagnosis usually needs confirmation and, depending on the case, further tests to establish the origin. It is not a blood test to have without medical preparation.

When it is recommended

Resistant hypertension, or hypertension that is hard to control with several medicines
Hypertension with low potassium, whether spontaneous or related to diuretics
Early-onset or particularly severe hypertension
Hypertension together with an incidentally discovered adrenal nodule
A family history of primary aldosteronism or early hypertension
Screening of a person with hypertension when their doctor considers it appropriate to follow the broader recommendation of the 2025 guideline

Clinical comment

Primary aldosteronism is more common than was thought some years ago, and its consequences go beyond the blood pressure reading. The Endocrine Society's 2025 guideline suggests extending screening to everyone with hypertension, although the practical decision depends on the context and on whether the follow-up tests can be carried out properly.

Here the preparation is part of the test. Mineralocorticoid receptor antagonists, diuretics, beta blockers, ACE inhibitors and angiotensin II receptor blockers can change aldosterone, renin or their ratio. That does not mean they all have to be withdrawn in everyone. Only the doctor in charge can decide which medication is continued, replaced or stopped, and for how long.

In addition, potassium has to be corrected and the sample requires specific conditions of time and posture. Without these precautions, false positives or false negatives can occur. Bear in mind that an abnormal ratio opens the investigation, but does not establish the diagnosis on its own.

Dr. Antonio Mas

What is tested

Aldosterone: An adrenal hormone that regulates sodium, potassium and blood pressure.
Renin (plasma renin activity): Reflects the activity of the system that stimulates aldosterone production and has to be interpreted together with it.
Aldosterone/renin ratio: The screening test for primary aldosteronism. A high result guides the investigation, but it does not confirm the diagnosis on its own.
Sodium and potassium: Help interpret the aldosterone-renin system. Low potassium can reduce aldosterone and produce a misleading result.
Creatinine and eGFR: Assess kidney function, which influences blood pressure and the interpretation of the test.

How to prepare

Talk first to the doctor who manages your hypertension. Do not change or stop any medicine on your own. The sample is taken while fasting, in the morning, after you have been up and about for at least two hours and seated for 5 to 15 minutes. Do not restrict salt in the days before unless a doctor tells you to, and make sure your potassium has been checked.

You can add

Without another needle. It is offered when you order, so you do not have to decide now.

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Related blood tests

We have other profiles in Heart and diabetes with more or fewer tests:

The most comprehensive is not always the most useful. If you are not sure, the one we recommend to start with is Cardiovascular risk blood test with ApoB and Lp(a).

What it is based on

Adler GK, et al. · The Journal of Clinical Endocrinology & Metabolism 110(9):2453-2495
Primary Aldosteronism: An Endocrine Society Clinical Practice Guideline
Proposes screening for primary aldosteronism in everyone with hypertension, by measuring aldosterone and renin and calculating the ratio between them. It also sets out the conditions without which the result cannot be read: a morning sample taken while seated, potassium measured at the same time and prior withdrawal of interfering medicines. That is why this blood test has to be prepared with the doctor who manages your blood pressure.

Protocol designed by Dr. Antonio Mas, specialist in Endocrinology and Nutrition, Spanish medical licence no. 080846289, and reviewed in September 2026.

This blood test is a standardised protocol and does not replace a medical consultation. If you have symptoms, a known condition or a complex clinical situation, speak to your doctor.