Your kidneys play an essential role in your body. They filter your blood, removing waste and excess fluid. And they perform a host of other key functions, like balancing your electrolytes, regulating your blood pressure, activating vitamin D (to help you absorb calcium and keep your bones strong), and helping your body produce red blood cells. Kidney disease affects over 1 in 7 Americans—about 35.5 million people—but because its symptoms are so subtle, many people don’t realize they have it.
“Symptoms of kidney damage are typically very subtle, and by the time you notice them, there is usually already serious harm done,” says Jeremy Allen, D.O., a board-certified family practitioner. “It is possible to lose as much as 90% of kidney function without having any overt symptoms.”
One great way to protect yourself is to keep your blood sugar and blood pressure under control. “Hypertension and diabetes are the main culprits, responsible for at least two-thirds of renal failure,” says Jonathon Shaffer, M.D., an internist affiliated with Concierge Choice Physicians.
You can also ask for a full blood workup at your annual checkup—and review any medications you’re currently taking. If your bloodwork shows high levels of the waste product creatinine, your doctor might order additional blood tests, urine tests, or kidney scans. Likewise, Allen says your doctor can help you pinpoint medications that are toxic to your kidneys—“like some NSAIDs, certain antibiotics, or lithium or iodine-containing medications”—and suggest other treatments.
But if something seems amiss, don’t wait until your annual exam to bring it up. While kidney disease is often silent, there are some warning signs that can help you catch it early—as long as you know what to look for.
Swelling and Weight Gain
Your kidneys remove waste and excess fluid from your body by producing urine. “If the kidneys slow down or do not work well, then fluid can be retained,” says Mateo Ledezma, M.D., a nephrologist with Kaiser Permanente. “This can result in persistent swelling in tissue.” This type of swelling is called edema.
Infrequent Urination
When more fluid is stuck in your tissues, less is being flushed out—meaning you may be peeing less than usual. If you notice you’re drinking the same amount you normally do, but urinating less frequently, it may be worth bringing up with your doctor.
Fatigue
“Part of the function of the kidneys is to help regulate a person’s hemoglobin level,” says Ledezma. Hemoglobin is a protein in your red blood cells that helps circulate oxygen throughout the body. When something goes wrong with your kidneys, your hemoglobin levels can drop and you can become anemic—making you feel tired and weak.
Nausea or Loss of Appetite
When waste builds up in your system because your kidneys aren’t filtering it out, it can start to mess with other parts of your body. This can lead to nausea, vomiting, and loss of appetite and just generally make you feel sick.
Brain Fog
Waste build-up can also affect your brain, causing you to feel like you can’t think clearly. Pay attention to symptoms like forgetfulness, trouble concentrating, confusion, and brain fog, especially if they’re out of character for you.
High Blood Pressure
Once your kidneys are damaged, they can’t effectively regulate your blood pressure. And this causes an unfortunate cycle. The force of your blood pounding against your vessels stretches them, causing further damage by scarring and weakening the blood vessels in your kidneys.
Heart Palpitations
“If your kidney damage is causing a build-up of potassium, you might notice an abnormal heartbeat,” says Allen. Your heartbeat might seem fast or irregular, or you may feel like your heart is fluttering.