A Renin blood test or Renin assay is a diagnostic process to find the exact causative factor of hypertension to module a correct treatment plan. Also known as plasma renin activity (PRA) or aldosterone-renin ratio (ARR), it mainly helps to find out what is happening within the body.

What Is Hypertension?

Hypertension or High Blood Pressure is quite a common heart anomaly tormenting almost 26% of the world’s populace wherein the arterial blood pressure increases to higher levels ultimately leading to heart attacks, strokes, and sometimes even death. Although there can be plenty of factors that contribute towards high blood pressure, the most common ones include sedentary lifestyle, excessive intake of sodium, smoking, alcohol consumption, insomnia, stress, obesity, age, family history, lifestyle habits etc.

Also Read: Hypertension: Am I At Risk?
aldosterone test

What Is Renin?

Renin is an enzyme produced by specialized cells within the kidney that chiefly works by controlling the blood pressure. It primarily works with aldosterone (a hormone made by the adrenal glands) and several other substances to help bring a balance of the sodium and potassium levels and other fluid levels within the blood, which affect the blood pressure.

How Does Renin Work?

When there is a drop in the blood pressure or the body doesn’t have enough salt, the body sends renin into the bloodstream. This action triggers a chain reaction that creates a hormone called angiotensin which signals the adrenal glands to release another hormone called aldosterone. While angiotensin makes the tiny blood vessels narrower, aldosterone mainly functions by telling the kidneys to hold on to salt and fluid. Both aldosterone and renin can raise the blood pressure. If this process gets out of balance, the blood pressure can get too high.

What Is The Significance Of A Renin Test?

The Renin test mainly helps to analyse if the adrenal glands are making too much or too little of aldosterone. The test is especially useful in diagnosing Primary Aldosteronism (PA), a disease that chiefly stems from having too much aldosterone in the blood. PA, also known as primary hyperaldosteronism or Conn syndrome, causes high blood pressure. If not treated on time, high blood pressure increases the risk of stroke, heart attack, and kidney failure.

The doctor mostly does the renin and aldosterone test at the same time to find the renin to aldosterone level calling it plasma renin activity test or an aldosterone-renin ratio. In some people, it may be normal to have high blood levels of both renin and aldosterone. But if renin levels are low and aldosterone levels are high, it usually indicates the presence of a tumor in the adrenal glands.

Why Does A Person Need A Renin Test?

The doctor usually suggests for a renin test if the patient is already diagnosed with high blood pressure, but the treatment plan chalked up or the medicines prescribed isn’t working for him or her. The Renin test helps to detect the cause so that it can be treated effectively.

In some cases, due to Primary Aldosteronism, the potassium levels in the blood may depreciate. The doctor may suggest a renin test if you show the following symptoms of low potassium including:

  • Fatigue
  • Headache
  • Cramps
  • Weakness
  • Excessive thirst

How To Prepare For The Renin Test?

The doctor may suggest restricting the intake of certain medications 2-4 weeks before going for the test. These include:

  • Diuretics
  • Birth control pills (estrogens)
  • High blood pressure medicines (especially beta-blockers and ACE inhibitors)

In such cases the doctor may suggest an alternative medication that will not affect the test results.

The doctor also asks the patient to stop the consumption of natural black licorice for 2 weeks before the test and avoid eating or drinking foods that contain caffeine the day before the test. Additionally, he or she may ask the patient to opt for a low-sodium diet for 3 days before the renin test.

What Is The Procedure Of A Renin Test?

At first the health care professional or phlebotomist asks the patient to sit or lie down to relax for 1 to 2 hours before the blood is collected. He or she usually draws the blood sample from a vein in the arm, using a small, sterilized needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. It usually feels like a little sting when the needle goes in and out. In some cases, a second blood sample may be collected after you move around for 1-2 hours.

What Are The Risks Of A Renin Test?

There are usually no reported side effects from taking a renin test apart from slight pain and bruising at the puncture site that too only for some time after which it usually subsides on application of an ice pack or on its own. In very rare case scenarios, there were reports of infection at the puncture site, excessive bleeding, fainting or dizziness, multiple punctures to locate pain, hematoma or any infection.

How To Interpret The Results?

In case a person undergoes a normal sodium diet, the normal value range is 0.6 to 4.3 ng/mL/hour (0.6 to 4.3 µg/L/hour). For low sodium diet, normal value range is 2.9 to 24 ng/mL/hour (2.9 to 24 µg/L/hour).

The normal value ranges may slightly differ among various laboratories. It is necessary to consult the doctor regarding the test results to interpret it accurately.

If your results show a higher-than-normal amount of renin, it may indicate that you have:

  • Addison disease
  • Liver cirrhosis
  • Dehydration
  • Excessive bleeding (haemorrhage)

If your results show a lower-than-normal amount of renin, it may depict that you have:

In most cases, the doctor usually compares the renin test results with aldosterone test results. These results may show one of the following:

  • Lower than normal renin/Lower than normal aldosterone: Indicates you may have Cushing’s syndrome
  • Lower than normal renin/Higher than normal aldosterone: Means you may have Primary aldosteronism (PA)
  • Higher than normal renin/Lower than normal aldosterone: Signifies that you have Addison’s disease.
  • Higher than normal renin/Higher than normal aldosterone: This may mean you have Secondary aldosteronism.

Depending upon the results, the doctor then recommends necessary medications and devises an accurate treatment plan alongside proper diet and lifestyle changes to treat your condition effectively.

Also Read: Some effective home remedies to tackle Hypertension