Even mild kidney damage increases your chances of having a heart attack or stroke, or dying from one of these. And heart disease may be a warning sign that you have problems with your kidneys. A big reason for this correlation is that both conditions often stem from the same sinister sources—high blood pressure, cholesterol- clogged arteries, inflammation, and high blood sugar.

In a way, that’s good news, because it means that treating heart disease often helps the kidneys, and vice versa. If the heart is the body’s engine, the fist-sized kidneys are part of its cleanup crew. They chemically filter the blood to remove waste products, toxins, and excess fluid.

They regulate blood pressure and oversee the crucial balance of nutrients such as sodium, potassium, and calcium. And they make several vitamins and hormones. Although the kidneys are tough, resilient workers, they aren’t indestructible. Years of elevated blood pressure can damage them.

Blood flow impeded by cholesterol-narrowed arteries causes problems in the kidneys, as do the high blood sugar and artery damage that accompany diabetes. In fact, the duo of high blood pressure and diabetes causes almost two-thirds of cases of kidney damage. Infection and inflammation account for most of the rest.

Kidney damage usually goes unnoticed until it’s too late. By the time symptoms such as fatigue, poor appetite, weight loss, and itching appear, little healthy kidney remains. At this point, it may be necessary to start dialysis, essentially having a machine filter the blood three times a week.

Doctors use several yardsticks to measure kidney health. If you have heart disease, don’t be surprised if your doctor asks you to get these tests. If he or she doesn’t bring it up, you should.

• Creatinine level. Creatinine is a waste product that comes from the normal wear and tear of muscles. Healthy kidneys filter most of it out of the blood; weakened ones don’t. So a simple blood test for creatinine offers a snapshot of your kidneys’ health.

• Glomerular filtration rate (GFR). This measure—a calculation based on your creatinine level—estimates how well your kidneys remove wastes and fluids from your bloodstream. The higher the GFR, the better the filtration.

• Protein level. Most proteins in the bloodstream are too large to pass into the kidneys’ millions of tiny filters (glomeruli). Damaged kidneys, though, let proteins pass into the urine. Checking the urine for protein, even at low levels, can serve as an early warning sign of kidney disease.

The following steps will help control damage to your kidney and heart.

• Control your blood pressure.

• Go easy on protein. There’s some evidence that a highprotein diet can further weaken borderline or damaged kidneys by boosting blood pressure inside of them. If you eat a lot of protein, think about cutting back.

• Ask your doctor if you’re on all the appropriate heartprotecting medicine. People who have both kidney disease and heart disease are less likely to get aspirin, beta-blockers, and statins than those who have just heart disease. Some doctors worry that these drugs may further damage the kidneys.

But a growing body of evidence indicates that the ability of these drugs to prevent heart attacks and strokes outweighs the possible negative effects they may have on the kidneys. However, this decision depends on a lot of individual factors, so talk with your kidney specialist.

• Check with your doctor before taking yellow-light drugs. Routine use of painkillers such as full-dose aspirin, ibuprofen, COX-2 inhibitors, and other nonsteroidal antiinflammatory drugs can be hard on the kidneys. Acetaminophen is a good alternative.