Renin is an enzyme made by your kidneys that kicks off a hormone cascade to raise blood pressure and balance salt and water in your body.

Quick Scoop: What does renin do?

  • Renin is released by special cells in the kidney (juxtaglomerular cells) when:
    • Blood pressure drops.
    • Blood flow to the kidney decreases.
    • Sodium (salt) levels reaching the kidney tubules are low.
  • Once released, renin:
    • Cuts a protein from the liver called angiotensinogen into angiotensin I.
* Angiotensin I is then converted (mainly in the lungs) into angiotensin II by ACE (angiotensin‑converting enzyme).
  • Angiotensin II then:
    • Constricts blood vessels (vasoconstriction), increasing blood pressure.
* Stimulates the adrenal glands to release aldosterone, which makes the kidneys retain sodium and water and excrete potassium.

* Stimulates release of ADH (vasopressin) and triggers thirst, helping the body hold onto more water.
  • Overall effect:
    • Raises blood pressure.
    • Increases blood volume.
    • Helps keep sodium, potassium, and fluid levels in balance (the renin–angiotensin–aldosterone system, or RAAS).

In simple terms: renin is the “starter switch” of a hormone system that tightens vessels and saves salt and water so your blood pressure and kidney perfusion don’t fall too low.

TL;DR: Renin itself doesn’t directly squeeze vessels, but by activating the RAAS chain (angiotensin and aldosterone), it helps your body correct low blood pressure and low blood volume.

Information gathered from public forums or data available on the internet and portrayed here.