High blood pressure and your kidneys

If you have pressure, this page is for you

Many people who are told they have high blood pressure (hypertension) think of it as a heart problem, or simply as "pressure" to be managed with tablets. That is partly right. But the kidneys and blood pressure are closely linked, and people with high blood pressure are often advised to have simple kidney tests, even when they feel completely well.

You do not need to have kidney symptoms to benefit from reading this. Early kidney changes linked to blood pressure usually cause no symptoms at all.

How blood pressure affects the kidneys

Each kidney contains around a million tiny filtering units. Each unit has a small knot of very fine blood vessels, called a glomerulus, that filters the blood. These vessels work best at a steady, moderate pressure.

When blood pressure stays high for months and years, it can damage and narrow these small vessels. Damaged filters may start to let albumin, a protein, leak into the urine, and over time they may filter less blood. Together, diabetes and high blood pressure are the two most common causes of chronic kidney disease (CKD) worldwide.

Kidney disease and high blood pressure

The link works in both directions. Healthy kidneys help control blood pressure by removing extra salt and water and by releasing hormones that affect the blood vessels. When the kidneys are damaged, the body can hold on to more salt and fluid, and blood pressure tends to rise. Higher pressure can then cause more kidney damage.

This is why most people with CKD also have high blood pressure, and why keeping blood pressure in the range agreed with a doctor is a central part of caring for the kidneys. See chronic kidney disease.

What kidney tests may be used

Guidance such as NICE NG136 advises that people newly found to have high blood pressure have tests that include their kidneys. Commonly used tests are:

• Urine ACR (albumin to creatinine ratio), which looks for albumin in the urine. About urine ACR.
• Blood creatinine with eGFR. The lab uses a validated equation to turn creatinine into an eGFR, an estimate of how well the kidneys filter. About eGFR.
• A urine test for blood, often as part of a urinalysis.

Creatinine alone does not tell the whole story. Reference ranges vary by lab, age, sex and muscle mass. Doctors look at eGFR and urine ACR together, and repeat them over time, before deciding whether there is kidney disease. See kidney function tests.

Why monitoring matters

High blood pressure and early kidney disease are both usually silent. Regular checks help in three ways:

• Blood pressure readings show whether pressure is staying in the range agreed with your doctor. Some people are asked to check at home or at a pharmacy and write the readings down.
• Kidney tests over time show whether kidney function is stable. A single result is less useful than the trend.
• Medicine reviews make sure your treatment still suits your kidney function. Some blood pressure medicines can change creatinine or potassium levels, so doctors often check blood tests after starting or changing them.

Please do not stop or change blood pressure medicine on your own because of a test result. Discuss it with your doctor first.

Questions to discuss with a clinician

• Have my kidneys been checked, and which tests were done?
• What were my eGFR and urine ACR results?
• What blood pressure range should I aim for?
• Should I check my blood pressure at home, and how often?
• Could any of my medicines affect my kidneys?
• How often should my kidney tests be repeated?
• Would it help to see a kidney specialist?

More ideas are on our questions to ask your doctor page.

Finding kidney or internal medicine care in Mombasa

For most people with high blood pressure, the first point of care is a general doctor or a physician (a specialist in internal medicine). They can arrange kidney tests at a lab or hospital outpatient clinic and explain the printed results. A nephrologist, a doctor who specialises in the kidneys, may become involved if kidney results are abnormal, are changing quickly, or if blood pressure stays high despite several medicines. See when to see a nephrologist and kidney care in Mombasa.

Frequently asked questions

I have high blood pressure but feel fine. Do I need kidney tests?

Many guidelines advise kidney tests for people with high blood pressure, because early kidney changes usually cause no symptoms. Ask your doctor whether you have had a urine ACR and a creatinine with eGFR, and when they should be repeated.

Can kidney problems cause high blood pressure?

Yes. Damaged kidneys can hold on to more salt and water and change hormone signals that control blood vessels, which can raise blood pressure. This is one reason doctors check the kidneys when someone has high blood pressure.

Can my blood pressure tablets harm my kidneys?

Some blood pressure medicines can change creatinine or potassium levels, which is why doctors often repeat blood tests after starting or changing them. Many of these medicines are also used to help protect the kidneys. Do not stop any medicine without talking to your doctor.

This page explains what a test or condition involves. It is not a diagnosis and does not replace advice from a doctor who knows your history. Your results should be interpreted together with your symptoms, other tests and a clinical assessment. Medical disclaimer.