Kidney pain is a deep, steady ache felt in your flank, the area on either side of your spine just below your rib cage and above your hips. Unlike lower back pain, it doesn’t get better or worse when you shift positions. Stopping it depends entirely on what’s causing it, but there are effective steps you can take right now to ease the discomfort while you figure out the source.
Make Sure It’s Actually Your Kidneys
The kidneys sit against the back muscles just below the rib cage, so kidney pain and back pain can feel like they’re coming from the same place. The key difference is movement. Lower back pain typically worsens with certain motions and improves when you find a comfortable position. Kidney pain does not change with movement. It stays constant whether you’re lying down, standing, or stretching.
Kidney pain also tends to feel deeper than muscle pain. It’s usually one-sided, though it can affect both flanks. If the pain radiates downward toward your groin or comes in intense waves, that pattern points strongly toward a kidney stone moving through your urinary tract. If the pain comes with fever, chills, or burning during urination, an infection is the more likely culprit.
The Two Most Common Causes
Kidney stones and urinary tract infections that have spread to the kidneys (kidney infections) account for the vast majority of kidney pain. These two conditions feel different, progress differently, and require different treatment.
Kidney stones form when minerals in your urine crystallize and clump together. The pain hits when a stone moves into your ureter, the narrow tube connecting your kidney to your bladder. This produces sudden, severe waves of pain that many people describe as the worst they’ve ever experienced. You may also notice pink, red, or brown urine, nausea, or a persistent urge to urinate.
Kidney infections usually start as a lower urinary tract infection that travels upward. The pain is more of a constant, deep ache in one flank, often accompanied by fever, chills, nausea, and painful urination. This is a condition that requires antibiotics. Without treatment, it can become serious quickly.
Immediate Steps to Ease the Pain
While you work on getting a diagnosis, a few things can help reduce the discomfort at home.
Apply heat to your flank. Place a heating pad or warm water bottle against the painful side of your back, between your ribs and hip. Heat soothes irritated nerves and relaxes the surrounding muscles. Cover the heating pad with a cloth to protect your skin, and limit each session to 10 to 15 minutes at a time.
Drink more water. Staying well hydrated helps flush bacteria out of your urinary tract if an infection is involved, and it keeps urine flowing around a stone. If you suspect a stone, steady water intake throughout the day is one of the most effective things you can do. Avoid coffee, other caffeinated drinks, and alcohol until you know what’s going on, as these can irritate your urinary system or contribute to dehydration.
Choose the right pain reliever. Acetaminophen (Tylenol) is generally safe for kidney pain and can help with both fever and discomfort. NSAIDs like ibuprofen (Advil, Motrin) and naproxen (Aleve) are effective pain relievers, but they can be harmful if you have any degree of kidney disease. People with reduced kidney function, heart failure, high blood pressure, or liver disease should avoid NSAIDs entirely. If you’re not sure about your kidney health, acetaminophen is the safer choice.
When the Cause Is a Kidney Stone
Small stones often pass on their own with time and hydration. The goal is to produce enough urine to keep things moving. Urologists recommend a fluid intake that produces at least 2.5 liters of urine per day, which typically means drinking about 3 liters of water. That’s roughly 12 to 13 cups spread throughout the day, not all at once.
Stones smaller than about 5 to 6 millimeters have a reasonable chance of passing without intervention, though the process can take days to weeks and the pain can come in unpredictable waves. Larger stones or stones that get stuck may need a procedure. The two most common options are shockwave therapy, which uses sound waves from outside the body to break the stone into smaller pieces, and ureteroscopy, where a thin scope is passed through the urinary tract to remove or break up the stone directly. Both are minimally invasive, and most people go home the same day.
A non-contrast CT scan is the gold standard for diagnosing kidney stones, with 95% or higher sensitivity and specificity. It shows the exact size and location of a stone, which helps determine whether it’s likely to pass or needs intervention. For pregnant patients, ultrasound is the preferred imaging tool because it avoids radiation exposure.
When the Cause Is a Kidney Infection
Kidney infections require antibiotics. There is no effective home remedy that replaces them. Symptoms typically begin to clear up within a few days of starting treatment, but you’ll usually need to complete a full course of antibiotics even after you feel better.
While the antibiotics take effect, you can manage the pain with heat applied to your back or side, acetaminophen for fever and discomfort, and plenty of water to help flush bacteria. The combination of these supportive measures with antibiotics resolves most kidney infections without complications.
Preventing Future Kidney Pain
If you’ve had kidney stones once, your risk of getting them again is significant. Dietary changes make a measurable difference in recurrence rates.
Stay on top of hydration permanently. The single most effective prevention strategy is drinking enough fluid every day to produce at least 2.5 liters of urine. This dilutes the minerals that form stones and keeps them from crystallizing. Water is the best choice. Make it a daily habit, not something you do only when you remember.
Cut back on sodium. High sodium intake increases the amount of calcium your kidneys filter, which raises stone risk. Adults should aim for less than 2,300 mg of sodium per day, roughly one teaspoon of table salt. Most of the sodium in American diets comes from processed and restaurant foods, not the salt shaker, so reading labels matters more than putting down the salt at dinner.
Watch high-oxalate foods if you form calcium oxalate stones. These include spinach, rhubarb, beets, nuts, and chocolate. You don’t necessarily need to eliminate them, but pairing them with calcium-rich foods (like dairy) at the same meal helps bind oxalate in the gut before it reaches your kidneys. A dietitian or your doctor can give you specific guidance based on your stone type.
For kidney infections, prevention centers on keeping bacteria out of your urinary tract. Staying hydrated, urinating when you feel the urge rather than holding it, and wiping front to back all reduce the chance of bacteria traveling upward to the kidneys.
Signs You Need Emergency Care
Most kidney pain can be evaluated during a regular medical visit, but certain symptoms signal that you need care right away. Seek emergency attention if you experience a fever above 101.3°F (38.5°C) alongside flank pain, if you notice a significant drop in how much you’re urinating or stop urinating altogether, or if you see blood in your urine combined with severe pain. Persistent vomiting that prevents you from keeping fluids down is another reason to go in, because dehydration can worsen both stones and infections.
If your abdomen feels swollen and tight, or you notice unusual swelling in your legs and feet alongside kidney pain, that can indicate fluid retention from impaired kidney function. These symptoms warrant immediate evaluation rather than a wait-and-see approach.