Pain on the left side of your abdomen can come from dozens of different causes, ranging from trapped gas to kidney stones to conditions that need urgent treatment. The left side of your belly houses parts of your stomach, pancreas, spleen, left kidney, and a long stretch of your large intestine, so pinpointing the cause often comes down to exactly where the pain is, how it feels, and what other symptoms come with it.
Upper Left Side: Stomach, Spleen, and Pancreas
Pain in the upper left area, roughly beneath your lower ribs, typically involves your stomach, spleen, or pancreas. The most common culprits are straightforward: gastritis (inflammation of the stomach lining), indigestion, or a stomach ulcer. These tend to cause a burning or gnawing ache that gets worse after eating, sometimes with nausea or a feeling of fullness that seems out of proportion to what you ate.
An enlarged spleen can produce a dull ache or feeling of fullness in the upper left that sometimes radiates to your left shoulder. You might notice you feel full quickly when eating because the swollen spleen presses against your stomach. Pancreatitis, inflammation of the pancreas, causes pain in the upper middle or upper left abdomen that can be severe and steady, often worse after meals and sometimes radiating straight through to your back. It frequently comes with nausea, vomiting, and a tender, swollen belly.
Trapped Gas and Splenic Flexure Syndrome
One of the most common and least serious causes of upper left abdominal pain is simply gas stuck in the wrong spot. Your large intestine makes a sharp bend near your spleen called the splenic flexure, and it’s the highest point in the colon. Gas naturally rises, so it tends to collect there. When it does, the colon stretches and triggers bloating, fullness, and a crampy or sharp pain in the upper left abdomen. This is sometimes called splenic flexure syndrome. The pain can feel alarming, but it usually eases once the gas moves through. It’s more common in people who already deal with bloating or irregular bowel habits.
Irritable Bowel Syndrome
IBS frequently causes pain on the left side because the descending colon, which runs down the left side of your abdomen, is often the most sensitive stretch of bowel. People with IBS have oversensitive nerve endings in the digestive tract, so small bubbles of gas that wouldn’t bother most people can be genuinely painful. The pain tends to come and go, often improves after a bowel movement, and travels alongside changes in stool consistency or frequency. Bloating and visible swelling of the belly are common companions.
Lower Left Side: Diverticulitis and Colon Issues
Pain specifically in the lower left abdomen, below your belly button and toward your hip, raises different possibilities. The most well-known is diverticulitis, an infection or inflammation of small pouches that form in the colon wall. It typically hits people over 40 and causes steady, persistent pain in the lower left that builds over a day or two, often with fever, nausea, and a change in bowel habits. A CT scan of the abdomen is the standard way to confirm the diagnosis.
Inflammatory bowel disease, particularly a form that affects the colon, can also cause recurring lower left pain along with diarrhea (sometimes bloody), urgency, and weight loss. Constipation alone is another frequent cause. Stool tends to accumulate in the descending and sigmoid colon on the left side, and when it backs up, the stretching and pressure can produce a deep, crampy ache that resolves once you have a bowel movement.
Kidney Stones
A stone in your left kidney or the tube connecting it to your bladder (the ureter) causes a distinctive kind of pain: sharp, severe, and located in the side and back below the ribs, often spreading toward the lower abdomen and groin. The pain comes in waves, surging and then easing before surging again. It’s frequently described as the worst pain a person has experienced. Other signs include pain or burning during urination, blood in the urine (which may look pink or red), nausea, and vomiting. A kidney infection on the left side can cause similar flank pain, usually with fever and chills.
Gynecological Causes
For people with ovaries, left-sided abdominal pain has a whole additional category of possibilities. An ovarian cyst on the left ovary can cause a dull ache or sharp pain below the belly button on that side, along with bloating, fullness, or pelvic pressure. Most ovarian cysts are small, cause no symptoms, and resolve on their own within a few menstrual cycles.
Larger cysts carry more risk. They can cause the ovary to twist on itself, a condition called ovarian torsion, which triggers sudden, severe pelvic pain with nausea and vomiting. A cyst that ruptures can cause intense pain and internal bleeding. Endometriosis, where tissue similar to the uterine lining grows outside the uterus, can form cysts on the ovary and cause chronic, recurring pelvic pain that often worsens around menstruation. An ectopic pregnancy, where a fertilized egg implants outside the uterus (usually in a fallopian tube), causes severe abdominal pain and vaginal bleeding and is a medical emergency.
Muscle Strain and Nerve Pain
Not all left-sided abdominal pain comes from an organ. The abdominal wall itself, meaning the layers of muscle, fat, and connective tissue covering your belly, can be the source. A pulled or strained muscle from exercise, heavy lifting, or even a hard cough produces localized soreness that worsens when you move, twist, or tense your core. You can usually point to the exact painful spot with one or two fingers.
Nerve entrapment is another possibility, particularly after abdominal surgery. A small nerve in the abdominal wall gets pinched or irritated, causing chronic, well-localized pain that flares when anything presses on that spot or when you tense your abdominal muscles. Lying on the affected side often makes it worse. One clue that the pain is coming from the wall rather than an organ: it gets worse, not better, when you tighten your abs (like doing a partial sit-up). Internal organ pain typically stays the same or decreases with that movement.
How the Cause Gets Identified
Figuring out what’s behind left-sided abdominal pain starts with the basics: where exactly it hurts, what it feels like, how long it’s been going on, and what makes it better or worse. Blood and urine tests can flag infection, inflammation, or kidney problems. For many people, imaging is the next step.
A CT scan of the abdomen and pelvis with contrast is the go-to for undifferentiated abdominal pain, offering the best combination of sensitivity and detail. It can identify diverticulitis, kidney stones, appendicitis, pancreatitis, and many other causes in a single scan. Ultrasound is preferred as the first imaging choice for suspected gynecological causes and is also the safer option during pregnancy and for children, since it avoids radiation. MRI provides excellent images but is less commonly used in urgent settings because of cost and availability.
Signs That Need Immediate Attention
Most left-sided abdominal pain turns out to be something manageable: gas, a stomach bug, constipation, or a muscle pull. But certain patterns signal something more serious. Sudden, severe pain that doesn’t ease within 30 minutes warrants emergency care. So does abdominal pain paired with continuous vomiting, fever with a rigid or extremely tender belly, signs of shock (cold and clammy skin, rapid breathing, lightheadedness), or vaginal bleeding during early pregnancy. Severe pain that comes in waves alongside bloody urine points toward a kidney stone that may need treatment to pass.