The kidneys are vital to our health. They filter out toxins and deliver important nutrients to the bloodstream. However, when people develop chronic kidney disease (CKD), their kidneys become damaged and over time may not clean the blood as well as healthy kidneys. According to the Centers for Disease  Control and Prevention, CKD can lead to high blood pressure, heart disease, stroke and early death. Approximately 37 million Americans suffer from CKD and most don’t know it.

“There are a number of physical signs of kidney disease, but sometimes people attribute them to other conditions,” says Dr. Joseph Vassalotti, chief medical officer at the National Kidney Foundation. “Also, those with kidney disease tend not to experience symptoms until the very late stages, when the kidneys are failing or when there are large amounts of protein in the urine. This is one of the reasons why only 10% of people with CKD know they have it.”

Here are some signs to look for:

• Decreased need to urinate or difficulty urinating. “This sign could indicate a blockage somewhere in the urinary tract,” says Sean Marchese, a registered nurse with over 15 years of direct patient experience. “If left untreated, urinary waste can back up and create high levels of toxins within the kidneys. Kidney stones, blood clots and an enlarged prostate are common signs or urinary difficulty.”

• Increased need to urinate. On the other hand, if you feel the need to urinate more often, especially at night, this can also signal kidney disease. When the kidneys filters are damaged, it can cause an increase in the urge to urinate. Sometimes this can be a sign of a urinary infection or enlarged prostate in men, says the National Kidney Foundation.

• Retaining fluid in the extremities. According to Eat This, Not That!, a regular sign of kidney damage is retaining fluid in the legs, fingers, hands or abdomen. If you notice pressure marks that take time to fade, talk to your doctor about these potential signs of kidney damage.

• Chest pain, shortness of breath or irregular heartbeat. Marchese says that kidney damage can cause issues in the cardiac and respiratory systems when the organs cannot regulate blood pressure. “High blood pressure can make breathing difficult or cause the heart to work harder, leading to palpitations or an irregular heart rhythm,” she says.

• Blood in the urine. Healthy kidneys keep blood cells in place, but when they are damaged, these blood cells can start to “leak” out into the urine, says the National Kidney Foundation.

• Dry, itchy skin. Advanced kidney disease may involve mineral and bone disease because the kidneys are no longer able to keep the right balance of minerals and nutrients in the blood, resulting in skin changes.

To keep kidneys healthy, Marchese recommends avoiding high levels of over-the-counter medications such as aspirin, acetaminophen, ibuprofen, and other pain medications. “You should also undergo regular diabetes and blood pressure screenings with your primary care doctors and maintain a healthy lifestyle,” she adds.