Recumbent renin and aldosterone

Investigation Protocol


Investigation of suspected Conn’s syndrome and of unexplained hypokalaemia.


The patient can eat and drink normally prior to this test and take their medication as usual. Multiple medications interfere with this test and so it is essential that patients bring their medication with them to be documented.

The finding of an elevated aldosterone:renin ratio requires the medication to be reviewed, altered if necessary, and the test repeated.


Patients should have a blood test for serum potassium 10-14 days prior to the test. Low results must be discussed with referring clinician or registrar so potassium levels can be corrected prior to the test date.

The patient should lie recumbent for 30 minutes prior to performing the test. 

Take two plain clotted bottles, and one lithium heparin bottle of blood. The A lithium heparin bottle is taken for renin, and should be centrifuged, separated and the plasma frozen, labelled with patient details, date and time. The two plain bottles should also be labelled, and sent for urea and electrolytes, and for aldosterone but do not need to be centrifuged.

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Patient information sheet

Recumbent renin and aldosterone

Your doctor has asked us to coordinate a blood test to measure some very specialised hormones, which are produced in the adrenal gland. Unfortunately the samples must be taken when you have been lying down for 30 minutes, and into specially prepared bottles and then handled in a specific way after they are taken. This means that you cannot have them done at your GP surgery.

You can eat and drink and take your medication as normal before this test, although your doctor may have already altered your medication specially in advance of this. Please bring in all your medication with you so these can be documented on the day of this test.

You should expect your stay at the hospital to be about 45 minutes. You may bring someone to stay with you during the test but there is not enough space for more than one person. Children are discouraged, as this can be disruptive to other patients. However, if this poses a particular problem for you please discuss this with the senior nurse in the unit. You should be able to undertake normal activities after the test is finished and it should not interfere with your ability to drive home. 

If you have any queries about the test, please contact:

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