Plasma renin activity (PRA), angiotensinogenase.

Common Use:
To assist in evaluating for a possible cause of hypertension.

Plasma collected in a lavender-top (EDTA) or pink-top (K2EDTA) tube.

Normal Findings:
(Method: Radioimmunoassay)

Age and PositionConventional UnitsSI Units (Conventional Units × 1)
Newborn–12 mo2–35 ng/mL/hr2–35 mcg/L/hr
Supine, normal sodium diet
 1–3 yr1.7–11.2 ng/mL/hr1.7–11.2 mcg/L/hr
 4–5 yr1–6.5 ng/mL/hr1.0–6.5 mcg/L/hr
 6–10 yr0.5–5.9 ng/mL/hr0.5–5.9 mcg/L/hr
 11–15 yr0.5–3.3 ng/mL/hr0.5–3.3 mcg/L/hr
 Adult0.2–2.3 ng/mL/hr0.2–2.3 mcg/L/hr
Upright, normal sodium diet
 Adult–older adult1.3–4 ng/mL/hr1.3–4 mcg/L/hr
Values vary according to the laboratory performing the test, as well as the patient’s age, gender, dietary pattern, state of hydration, posture, and physical activity.


Renin is an enzymatic peptide hormone secreted by the granular cells of the juxtaglomerular apparatus in the kidney in response to sodium depletion and hypovolemia. Renin activates the renin-angiotensin system through the conversion of angiotensinogen to angiotensin I. Angiotensin I is converted to the biologically active angiotensin II by angiotensin-converting enzyme primarily within the capillaries of the lungs. Angiotensin II is a powerful vasoconstrictor that ultimately maintains the appropriate perfusion pressure in the kidneys. Angiotensin II stimulates aldosterone production in the adrenal cortex, secretion of antidiuretic hormone from the pituitary, and stimulates the thirst reflex from the hypothalmus. The net effect is regulation of blood pressure by regulating arterial vasoconstriction and the movement of extracellular fluids such as plasma, lymphatic fluid, and interstitial fluid. Excessive amounts of angiotensin II cause renal hypertension. The random collection of specimens without prior dietary preparations does not provide clinically significant information. Values should also be evaluated along with simultaneously collected aldosterone levels (see studies titled “Aldosterone” and “Angiotensin-Converting Enzyme”).

This procedure is contraindicated for



  • Assist in the identification of primary hyperaldosteronism resulting from aldosterone-secreting adrenal adenoma.
  • Assist in monitoring patients on mineralocorticoid therapy.
  • Assist in the screening of the origin of essential, renal, or renovascular hypertension.

Potential Diagnosis

Increased In:

  • Addison’s disease (related to hyponatremia, which stimulates production of renin)
  • Bartter’s syndrome (related to hereditary defect in loop of Henle that affects sodium resorption; hyponatremia stimulates renin production)
  • Cirrhosis (related to fluid buildup, which dilutes sodium concentration; hyponatremia is a strong stimulus for production of renin)
  • Gastrointestinal disorders with electrolyte loss (related to hyponatremia, which stimulates production of renin)
  • Heart failure (related to fluid buildup, which dilutes sodium concentration; hyponatremia is a strong stimulus for production of renin)
  • Hepatitis (related to fluid buildup, which dilutes sodium concentration; hyponatremia is a strong stimulus for production of renin)
  • Hypokalemia (related to decreased potassium levels, which stimulate renin production)
  • Malignant hypertension (related to secondary hyperaldosteronism that constricts the blood vessels and results in hypertension)
  • Nephritis (the kidneys can produce renin in response to inflammation or disease)
  • Nephropathies with sodium or potassium wasting (related to hyponatremia, which stimulates production of renin)
  • Pheochromocytoma (related to renin production in response to hypertension)
  • Pregnancy (related to retention of fluid and hyponatremia that stimulates renin production; normal pregnancy is associated with changes in the balance between renin and angiotensin)
  • Renin-producing kidney tumors
  • Renovascular hypertension (related to decreased renal blood flow, which stimulates release of renin)

Decreased In:

  • Cushing’s syndrome (related to excessive production of glucocorticoids, which increase sodium levels and decrease potassium levels, inhibiting renin production)
  • Primary hyperaldosteronism (related to aldosterone-secreting adrenal tumor; aldosterone inhibits renin production)

Critical Findings


Interfering Factors

  • Drugs and other substances that may increase renin levels include albuterol, amiloride, azosemide, benazepril, bendroflumethiazide, captopril, chlorthalidone, cilazapril, desmopressin, diazoxide, dihydralazine, doxazosin, enalapril, endralazine, felodipine, fenoldopam, fosinopril, furosemide, hydralazine, hydrochlorothiazide, laxatives, lisinopril, lithium, methyclothiazide, metolazone, muzolimine, nicardipine, nifedipine, opiates, oral contraceptives, perindopril, ramipril, spironolactone, triamterene, and xipamide
  • Drugs and other substances that may decrease renin levels include acetylsalicylic acid, angiotensin, angiotensin II, atenolol, bopindolol, bucindolol, carbenoxolone, carvedilol, clonidine, cyclosporin A, glycyrrhiza, ibuprofen, indomethacin, levodopa, metoprolol, naproxen, nicardipine, NSAIDs, oral contraceptives, oxprenolol, propranolol, sulindac, and vasopressin
  • Upright body posture, stress, and strenuous exercise can increase renin levels.
  • Recent radioactive scans or radiation can interfere with test results when radioimmunoassay is the test method.
  • Diet can significantly affect results (e.g., low-sodium diets stimulate the release of renin).
  • Hyperkalemia, acute increase in blood pressure, and increased blood volume may suppress renin secretion.
  • Failure to follow dietary restrictions before the procedure may cause the procedure to be canceled or repeated.

Nursing Implications Procedure

Related Studies


  • Positively identify the patient using at least two person-specific identifiers before services, treatments, or procedures are performed.
  • Patient Teaching: Inform the patient this test can assist in evaluating for high blood pressure.
  • Obtain a history of the patient’s health concerns, symptoms, surgical procedures, and results of previously performed laboratory and diagnostic studies. Include a list of known allergens, especially allergies or sensitivities to latex.
  • Note any recent procedures that can interfere with test results.
  • Obtain a list of the patient’s current medications, including over-the-counter medications and dietary supplements (see Effects of Dietary Supplements online at DavisPlus).
  • Review the procedure with the patient. Inform the patient or family member that the position required (supine or upright) must be maintained for 2 hr before specimen collection. Inform the patient that multiple specimens may be required. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • The patient should be on a normal sodium diet (1 to 2 g sodium per day) for 2 to 4 wk before the test. Protocols may vary among facilities.
  • By medical direction, the patient should avoid diuretics, antihypertensive drugs, herbals, cyclic progestogens, and estrogens for 2 to 4 wk before the test.
  • Prepare an ice slurry in a cup or plastic bag to have ready for immediate transport of the specimen to the laboratory.


Potential Complications:

  • Ensure that the patient has complied with diet and medication restrictions prior to the study, as instructed.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection online at DavisPlus. Positively identify the patient, and label the appropriate tubes with the corresponding patient demographics, date, and time of collection. Specify patient position (upright or supine) and exact source of specimen (peripheral vs. arterial). Perform a venipuncture after the patient has been in the upright (sitting or standing) position for 2 hr. If a supine specimen is requested on an inpatient, the specimen should be collected early in the morning before the patient rises.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • The sample should be placed in an ice slurry immediately after collection. Information on the specimen label should be protected from water in the ice slurry by first placing the specimen in a protective plastic bag. Promptly transport the specimen to the laboratory for processing and analysis.

Post Test

  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Instruct the patient to resume usual medications, as directed by the HCP.
  • Nutritional Considerations: Instruct the patient to notify the requesting HCP of any signs and symptoms of dehydration or fluid overload related to abnormal renin levels or compromised sodium regulatory mechanisms. Fluid loss or dehydration is signaled by the thirst response. Decreased skin turgor, dry mouth, and multiple longitudinal furrows in the tongue are symptoms of dehydration. Fluid overload may be signaled by a loss of appetite and nausea. Excessive fluid also causes pitting edema: When firm pressure is placed on the skin over a bone (e.g., the ankle), the indentation will remain after 5 sec.
  • Nutritional Considerations: Educate patients of the importance of proper water balance. In buildings with hard water, untreated tap water contains minerals such as calcium, magnesium, and iron. Water-softening systems replace these minerals with sodium, and therefore patients on a low-sodium diet should avoid drinking treated tap water and drink bottled water instead.
  • Nutritional Considerations: Renin levels affect the regulation of fluid balance and electrolytes. If appropriate, educate patients with low sodium levels that the major source of dietary sodium is found in table salt. Many foods, such as milk and other dairy products, are also good sources of dietary sodium. Most other dietary sodium is available through the consumption of processed foods. Patients on low-sodium diets should be advised to avoid beverages such as colas, ginger ale, sports drinks, lemon-lime sodas, and root beer. Many over-the-counter medications, including antacids, laxatives, analgesics, sedatives, and antitussives, contain significant amounts of sodium. The best advice is to emphasize the importance of reading all food, beverage, and medicine labels. The requesting HCP or nutritionist should be consulted before the patient on a low-sodium diet begins using salt substitutes. Potassium is present in all plant and animal cells, making dietary replacement fairly simple to achieve.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.
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