The aldosterone to renin ratio test, a blood test, measures the amount of aldosterone divided by the amount of renin in the blood plasma. The ratio is used as a way to determine whether or not primary hyperaldosteronism is occurring.

Aldosterone is one of the hormones that helps keep your sodium and potassium levels normal in the blood. It controls how much blood you have in the bloodstream, and thus your blood pressure. Aldosterone is created in the body by your adrenal glands. 

Renin is an enzyme created in the kidneys to control the production of aldosterone. Thus, it controls blood pressure levels indirectly through the activation of angiotensin hormones. The overall effect of renin is to increase the blood pressure.

Both aldosterone and renin levels vary during the day but their levels are at a peak in the morning. When aldosterone levels are increased higher than normal, the blood pressure increases and you will have low levels of potassium, headache and muscle weakness. Blood pressure that goes too high can cause a heart attack or stroke. 

This blood test may be ordered if high blood pressure medications are not working.

Normal Ranges for Aldosterone/Renin in ng/mL/hour:

Normal levels are dependent on how the test is performed and the time of the day. 

Generally speaking, the normal range is up to 23.6 ng/dL per ng/hour.

Critical range:  >23.6 ng/dL per ng/hour

Sources:

1. https://emedicine.medscape.com/article/920713-workup
2. https://labtestsonline.org/tests/aldosterone-and-renin