Yes, not drinking enough water can cause pain in your side. The most common reason is that dehydration concentrates your urine, which stresses your kidneys and can eventually lead to kidney stones or urinary tract infections, both of which produce noticeable side pain. But the connection isn’t always dramatic. Even mild, ongoing dehydration can create a dull ache in your flank area that you might not immediately link to your water intake.
Where Dehydration Pain Shows Up
Your kidneys sit behind your stomach, tucked under your rib cage on both sides of your spine. When dehydration affects them, you typically feel it as a deep ache in your side (what doctors call the “flank”), often under the ribs toward your back. This pain can stay in one spot or radiate toward your lower abdomen or groin. It’s usually deeper than a muscle cramp and harder to pinpoint with a finger.
The right side and left side are equally possible, since you have a kidney on each side. Some people notice the pain on just one side, while others feel it on both. If the discomfort comes and goes in waves or is sharp rather than dull, that’s more suggestive of a kidney stone moving through the urinary tract than simple dehydration strain.
How Low Water Intake Leads to Kidney Stones
When you consistently don’t drink enough, your body produces less urine, and the urine it does produce is more concentrated. That concentrated urine contains higher levels of dissolved minerals like calcium and oxalate. At a certain point, these minerals become supersaturated and begin to crystallize, forming kidney stones. This process is one of the single most common causes of kidney stone formation.
Small stones may pass without much trouble, but larger ones can get stuck in the ureter (the tube connecting your kidney to your bladder) and cause severe, wave-like pain in your side that ranks among the most intense pain people experience. The pain often shifts as the stone moves, starting high in the flank and migrating toward the groin. You may also notice pink or reddish urine, nausea, or a persistent urge to urinate.
Urinary Tract Infections and Side Pain
Low fluid intake is a recognized risk factor for urinary tract infections. When you drink enough water, your bladder flushes out bacteria regularly. When you don’t, bacteria have more time to multiply in stagnant, concentrated urine. Most UTIs start in the bladder, causing burning during urination and frequent bathroom trips. But if the infection climbs up to the kidneys, it produces back or side pain, often with fever, chills, and nausea.
A kidney infection is more serious than a bladder infection and needs prompt treatment. If you have side pain along with a fever above 102°F, confusion, blood in your urine, or a rapid heart rate, that combination points to something that needs medical attention quickly rather than just more water.
Constipation Can Cause Side Pain Too
Not all dehydration-related side pain comes from the kidneys. When you don’t drink enough water, your colon absorbs more fluid from the food passing through it, making stool harder and more difficult to move. The resulting backup can cause cramping and pressure that you feel in your sides or lower abdomen. Your large intestine wraps around your abdomen in a frame shape, so gas and stool trapped on the right side (near the ascending colon) or the left side (near the descending colon) can produce localized pain that mimics kidney problems.
This type of pain tends to feel more crampy than deep, and it often improves after a bowel movement. If you’ve been constipated and also drinking less than usual, increasing your water intake alone may resolve both the constipation and the side discomfort over a day or two.
How to Tell If You’re Dehydrated
The simplest check is your urine color. Pale yellow (like light straw) means you’re well hydrated. As you move toward darker yellow or amber, you’re progressively more dehydrated. Very dark urine with a strong smell, especially in small amounts, signals significant dehydration that needs attention. Other common signs include dry mouth, fatigue, headache, and dizziness when standing up quickly.
There’s no single water intake number that works for everyone. How much you need depends on your body size, activity level, climate, and whether you’re pregnant or breastfeeding. A practical approach: drink enough that your urine stays a light yellow color throughout the day. If you’re physically active, in hot weather, or recovering from an illness that causes vomiting or diarrhea, you’ll need more than usual.
When Side Pain Means Something Else
Dehydration is a real and common cause of side pain, but it’s not the only one. Muscle strains, rib injuries, and digestive issues like gas or inflammatory bowel conditions can all produce pain in the same area. Appendicitis causes right-side pain. Spleen problems cause left-side pain. Ovarian cysts can cause sharp pain on either side.
A few features help distinguish dehydration-related pain from something more urgent. Pain that responds to increasing your fluids over 24 to 48 hours and comes with dark urine is likely hydration-related. Pain that is sudden and severe, accompanied by fever, blood in your urine, vomiting, or that worsens when you press on the area suggests something beyond simple dehydration that warrants a closer look.