Serum or Plasma Renin Activity (measured as renin concentration)

What Renin Activity Measures

Renin is a key hormone in the **renin-angiotensin-aldosterone system (RAAS)**, which helps control blood pressure and fluid retention. This test checks how much renin your kidneys produce in response to certain conditions, such as low blood pressure or kidney issues. High or low renin levels may indicate problems with kidney function, blood pressure control, or other health conditions.

Why It’s Ordered

Your doctor may order this test if you have symptoms like high blood pressure, kidney problems, or conditions affecting fluid balance (e.g., heart failure, diabetes). It may also be used to diagnose or monitor certain kidney-related disorders or to evaluate responses to medications that affect blood pressure or fluid levels.

Common Reasons for Testing

Common reasons include evaluating kidney function, assessing blood pressure disorders (like primary aldosteronism), or checking for conditions like **pseudoaldosteronism** or **renovascular hypertension**. It may also be part of a broader evaluation for chronic kidney disease or other endocrine-related issues.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The sample is collected in a tube that separates serum or plasma from blood cells. This test does not require fasting, but timing of results may depend on your medical condition.