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.