Kidney pain calls for a combination of hydration, careful pain relief, and knowing when the cause requires medical treatment. What you should do depends on whether the pain stems from a kidney stone, an infection, or something else entirely. The first step is confirming the pain is actually coming from your kidneys, since it’s easy to confuse with ordinary back pain.
How to Tell It’s Your Kidneys
Kidney pain is felt in the flank, the area on either side of your spine just below your rib cage and above your hips. Unlike muscular back pain, which tends to be a dull ache that shifts when you change position, kidney pain doesn’t improve or worsen with movement. It stays constant and can spread to your lower abdomen or inner thighs.
The clearest giveaway is what accompanies the pain. Kidney problems often come with urinary changes: cloudy, dark, or bloody urine, a frequent or urgent need to pee, or pain during urination. Nausea, vomiting, fever, fatigue, and a metallic taste in your mouth also point toward a kidney issue rather than a pulled muscle. If you’re experiencing flank pain that doesn’t budge when you shift positions and you notice any of these additional symptoms, your kidneys are the likely source.
Immediate Steps You Can Take at Home
Drink more water than you normally would. For kidney stones specifically, the NHS recommends up to 3 liters (roughly 12 cups) of fluid per day to help flush the stone through your urinary tract. Even if you’re not sure a stone is the cause, staying well hydrated reduces strain on your kidneys and helps them filter waste more effectively. Spread your intake throughout the day rather than gulping large amounts at once.
Apply a heating pad to the painful area. Heat relaxes the muscles surrounding the kidney and ureter, which can ease the cramping and spasming that often accompanies stone movement or infection-related inflammation. Keep a cloth between the pad and your skin, and limit sessions to about 20 minutes at a time.
For pain relief, acetaminophen (Tylenol) is generally the safest option for your kidneys at recommended doses. NSAIDs like ibuprofen and naproxen reduce blood flow to your kidneys, which can lead to acute kidney injury, especially at higher doses or with prolonged use. If you have any existing kidney disease, you should avoid NSAIDs entirely. Even without kidney disease, use them only at the lowest dose for the shortest time necessary. People with heart disease, high blood pressure, or liver disease should also steer clear of NSAIDs.
If You’re Passing a Kidney Stone
About 80% of kidney stones pass on their own without surgical intervention. The timeline depends on size. A stone smaller than 4 millimeters typically passes within one to two weeks. Larger stones can take two to three weeks. The passage rates are encouraging for smaller stones: around 90% of stones under 6 mm will eventually pass, while about 60% of stones larger than 6 mm will too.
During this waiting period, your job is to keep drinking fluids and managing pain. Some people find it helpful to stay mildly active, as gentle movement can encourage the stone to shift. Your doctor may prescribe medication to relax the ureter and make passage easier. You’ll likely be asked to strain your urine so the stone can be analyzed, which helps determine what dietary changes might prevent future stones.
If a Kidney Infection Is the Cause
Kidney infections (pyelonephritis) hit harder than a simple bladder infection. They typically come on suddenly with fever, chills, severe flank pain, nausea, and vomiting. You may also notice painful or frequent urination. A urine test and culture confirm the diagnosis and identify which bacteria are responsible, most commonly E. coli.
Antibiotics are essential for kidney infections. Current treatment guidelines recommend 5 to 7 days of antibiotics for most cases, though some people may need up to 7 days depending on the specific medication used. This is shorter than the 10-to-14-day courses that were standard in the past. The clock starts from the first day you’re on an antibiotic that works against your particular bacteria. You’ll typically start feeling better within 48 to 72 hours, but finishing the full course matters to prevent the infection from returning or becoming resistant.
What Happens at the Doctor’s Office
If you go in for kidney pain, expect a urine test first. This checks for blood, bacteria, and signs of infection. Imaging usually comes next. Ultrasound is the recommended starting point because it avoids radiation exposure and is just as effective as a CT scan for detecting kidney stones. A large study following nearly 2,800 patients found that outcomes were equally good whether doctors used ultrasound or CT as the initial test. If the ultrasound doesn’t give a clear answer, your doctor may then order a CT scan for a more detailed look.
Blood tests can reveal whether your kidneys are functioning properly and whether an infection has spread to your bloodstream. These results, combined with imaging, help your doctor determine whether you can manage the problem at home or need more aggressive treatment.
Dietary Changes That Reduce Kidney Stress
What you eat matters, especially if kidney pain is a recurring problem. Sodium is the biggest dietary factor. Too much salt causes your body to retain fluid, which raises blood pressure and puts extra strain on your kidneys. The recommended limit is no more than 2,300 milligrams per day, but most people consume significantly more through processed foods, canned goods, deli meats, snack foods, and condiments like soy sauce and ketchup.
If you have any degree of reduced kidney function, you’ll also want to watch phosphorus and potassium. Phosphorus hides in processed foods under ingredient names containing “PHOS” (phosphoric acid, disodium phosphate). High phosphorus levels can damage blood vessels and weaken bones over time. Potassium, while essential, can build to dangerous levels when kidneys aren’t filtering well. Salt substitutes are a common hidden source of potassium, so use herbs and spices for flavor instead. Draining the liquid from canned fruits and vegetables also reduces their potassium content significantly.
Limiting saturated and trans fats protects both your kidneys and cardiovascular system. Red meat, fried foods, and commercially baked goods are the primary offenders. This doesn’t mean eliminating protein, but shifting toward leaner sources and being mindful of portion sizes.
When Kidney Pain Is an Emergency
Some symptoms alongside kidney pain warrant an emergency room visit rather than a wait-and-see approach. Go to the ER if you experience:
- Pain you can’t control with over-the-counter medication
- Inability to urinate at all
- Fever or chills, which suggest infection may be spreading
- Severe nausea or vomiting that prevents you from keeping fluids down
- Blood in your urine
- A constant, urgent need to urinate that’s unusual for you
- Persistent fatigue or feeling of illness that doesn’t improve
The inability to keep fluids down is particularly important because dehydration makes every kidney problem worse. If vomiting prevents you from drinking, you may need IV fluids to stay hydrated and keep your kidneys functioning. Fever combined with flank pain strongly suggests a kidney infection that could become dangerous without prompt antibiotic treatment.