Lab Test

Aldosterone, Serum

Test Codes



Send Outs


If an upright sample is requested, the patient should be upright (seated or standing) for at least 2 hours prior to specimen collection.

Specimen Collection Criteria

Collect (preferred specimen): One Gold-top SST tube.
Also Acceptable: One plain Red-top tube.

Send specimen for processing immediately after collection.

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transport serum to a plastic transport tube and freeze (-20°C/-4°F or below) immediately.

Preparation for Courier Transport

Transport: 1.0 mL serum, frozen (-20°C/-4°F or below). (Minimum: 0.6 mL)

Rejection Criteria

  • Grossly hemolyzed specimens.
  • Grossly lipemic specimens.
  • Specimens not collected and processed as indicated.
  • Heparin plasma.

In-Lab Processing

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transport serum to a plastic transport tube and freeze (-20°C/-4°F or below) immediately.

Transport: 1.0 mL serum, frozen (-20°C/-4°F or below). (Minimum: 0.6 mL)


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 5 days
Frozen (-20°C/-4°F or below): 1 month

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.


Sent to Warde Medical Laboratory, Ann Arbor, MI.


Monday, Wednesday, Thursday.
Results available in 1-4 days.

Reference Range

By report.

Test Methodology

Quantitative Chemiluminescent Immunoassay.


  • Normal serum levels of aldosterone are dependent on their sodium intake and whether the patient is standing or lying down.
  • High sodium intake will tend to decrease serum aldosterone levels. Low sodium intake will elevate serum aldosterone.
  • A high ratio of serum aldosterone (SA) in ng/dL to plasma renin activity (PRA) in ng/mL per hour, is a positive screening test result, a finding that warrants further testing. A SA/PRA ratio - 20 and SA - 15 ng/dL indicates probable primary aldosteronism. Renal disease, such as unilateral renal artery stenosis, results in elevated renin and aldosterone levels. Renal venous catheterization may be helpful. A positive test is a renal venous renin ratio (affected/normal) greater than 1.5.
  • Cautions: The plasma renin activity cannot be interpreted if the patient is being treated with spironolactone (Aldactone). Spironolactone (Aldactone) should be discontinued for 4-6 weeks before testing. Angiotensin converting enzyme (ACE) inhibitors have the potential to "falsely elevate" PRA. Therefore, in a patient treated with an ACE-inhibitor, the findings of a detectable PRA level or a low SA/PRA ratio do not exclude the diagnosis of primary aldosteronism. In addition, a strong predictor for primary aldosteronism is a PRA level undetectably low in a patient taking an ACE-inhibitor.

Clinical Utility

  • Aldosterone assays are useful in the diagnosis and treatment of aldosteronism, evaluation of adrenal function in non-edematous, hypertensive patient with alkalosis and hypokalemia, and in patients with adrenal hyperplasia accompanied by decreased renin.
  • The principal reason for the measurement of serum aldosterone is for the diagnosis of primary hyperaldosteronism which is most commonly caused by an aldosterone-secreting adrenal adenoma (rarely a carcinoma). About 10-15% of patients have bilateral adrenal hyperplasia and will not respond to unilateral adrenalectomy. This can be determined by measurement of differential adrenal vein aldosterone levels. This rare condition must be distinguished from secondary hyperaldosteronism, which is common, and may be found in association with cirrhosis, renal artery stenosis, renal cysts, nephrotic syndrome, or congestive heart failure.
  • Primary hyperaldosteronism should be suspected in patients who are hypertensive and hypokalemic. Urine potassium of less than 30 mmol/day essentially excludes the diagnosis.

CPT Codes

LOINC:  1763-2


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