Your kidneys are on both sides of your body, not just one. Most people have two kidneys, one on the left and one on the right, positioned toward the back of the abdomen on either side of the spine. They sit higher than many people expect, tucked up beneath the lower ribs rather than down near the hips.
Exact Position of Each Kidney
Both kidneys sit behind the abdominal cavity in a space called the retroperitoneal area, between the spine and the back muscles. They’re located roughly between the bottom of the rib cage and the third lumbar vertebra, which is about the level of your waistline. If you place your hands on your lower back just above your hips with your thumbs pointing toward your spine, your kidneys are roughly under your thumbs, deeper inside the body than you might think.
The right kidney sits slightly lower than the left. This asymmetry exists because the liver, a large organ on your right side, takes up space and pushes the right kidney down. The left kidney, with no large organ pressing on it from above, rides a bit higher. Each kidney is roughly the size of a fist. Median length is about 11.2 cm on the left and 10.9 cm on the right, so the left kidney is also slightly larger.
What Surrounds and Protects Them
The kidneys are protected by the 11th and 12th ribs, often called “floating ribs” because they only attach to the spine and not to the breastbone. This rib coverage shields the upper portion of each kidney from impact. Beyond the ribs, each kidney is wrapped in a layer of fat and enclosed in a tough fibrous capsule, adding cushioning against everyday movement and minor trauma.
Sitting on top of each kidney is a small, triangular adrenal gland. These glands produce stress hormones and help regulate blood pressure, but they function independently from the kidneys despite sharing the same neighborhood.
How to Tell Kidney Pain From Back Pain
Knowing where your kidneys are matters most when you’re trying to figure out whether a pain is muscular or kidney-related. Kidney pain is felt in the flank, the area on either side of the spine just below the ribs and above the hips. The spot where the lowest rib meets the spine, sometimes called the costovertebral angle, is the landmark doctors tap on during a physical exam to check for kidney tenderness.
Kidney pain and back pain feel different in important ways:
- Kidney pain does not worsen or improve with movement. It stays constant, doesn’t respond to changing positions, and often won’t get better without treatment. It can spread to the lower abdomen or inner thighs.
- Back pain is typically a dull ache or stiffness that gets worse with certain movements and improves when you shift into a more comfortable position. If nerves are involved, it may radiate down the legs.
Kidney-related pain can come from infections, kidney stones, or other conditions affecting the urinary tract. If you feel a deep, steady ache in your flank that doesn’t change when you move, that’s more likely kidney pain than a muscle strain. Fever, painful urination, or blood in the urine alongside flank pain strengthens that suspicion.
Why People Think Kidneys Are on One Side
The search “what side is the kidneys on” often comes from someone feeling pain on one side and wondering if a kidney is there. The answer is yes, whichever side you’re feeling it on. Pain from a kidney stone or infection almost always affects one kidney at a time, which is why it shows up as one-sided flank pain rather than pain across the whole lower back. Left-sided flank pain points to the left kidney, right-sided to the right. Because the right kidney sits lower, right-sided kidney pain can sometimes be mistaken for appendicitis or a gallbladder issue, while left-sided kidney pain can be confused with problems in the spleen or colon.