Pain on your left side can come from dozens of different structures, including your intestines, kidney, spleen, pancreas, ribs, and muscles. Where exactly you feel it, how it started, and what makes it worse are the biggest clues to narrowing down the cause. Most left-sided pain turns out to be something manageable, but a few causes need urgent attention.
Lower Left Abdomen
Diverticulitis
The most common cause of significant lower-left abdominal pain in adults over 40 is diverticulitis. Small pouches form along the wall of the large intestine, and when one becomes inflamed or infected, it produces pain that is usually sudden and intense. The lower left abdomen is the classic spot because that’s where the sigmoid colon sits.
The pain can start mild and build over hours, or hit sharply from the beginning. Fever, nausea, tenderness when you press on the area, and a sudden change in bowel habits (new diarrhea or constipation) often accompany it. If you have constant abdominal pain with fever and changes in your stool, that combination warrants medical evaluation.
Trapped Gas at the Splenic Flexure
Your colon makes a sharp bend near your spleen, called the splenic flexure. Gas traveling through the intestine can get stuck at this turn, producing bloating and surprisingly sharp pain in the upper-left or mid-left abdomen. Cleveland Clinic describes it like water rushing toward a sharp bend in a river: small amounts pass through fine, but a surge overwhelms the curve. This is sometimes called splenic flexure syndrome, and it can mimic more serious organ problems. It typically resolves on its own or with movement and passing gas, but because so many conditions share similar symptoms, providers sometimes need imaging to rule out other causes.
Inguinal Hernia
A left-sided inguinal hernia creates a visible or palpable bulge near your pubic bone. The bulge becomes more obvious when you stand up, cough, or strain. Pain tends to be a burning or aching sensation right at the bulge, and it flares with bending, lifting, or coughing. In men, the protruding tissue can descend toward the scrotum and cause swelling and pain there as well. Hernias don’t resolve on their own and typically require surgical repair.
Upper Left Abdomen
Pancreatitis
The pancreas sits behind the stomach, slightly left of center. When it becomes inflamed, it produces upper-belly pain that often radiates to the back or shoulders. A hallmark feature: the pain gets worse after eating. Acute pancreatitis comes on suddenly and can be severe. Chronic pancreatitis causes a more constant upper-belly ache that flares with meals. Gallstones and heavy alcohol use are the two most common triggers.
Enlarged Spleen
Your spleen sits tucked under your left rib cage. When it enlarges, it produces a vague discomfort in the left upper abdomen, sometimes with pain that refers to the left shoulder. You might also notice feeling full quickly when eating, bloating, or loss of appetite. An enlarged spleen isn’t a disease on its own but a sign of something else going on. Infections like mononucleosis, liver disease, blood cancers like lymphoma, and autoimmune conditions like lupus can all cause it. The biggest risk with an enlarged spleen is rupture, which can happen even with minor trauma. People with this condition are advised to avoid contact sports.
Left Flank and Back
Kidney Stones
A kidney stone on the left side causes flank pain, the area between your lower ribs and hip on your back. The pain is typically intense, comes in waves, and can shift downward toward your groin as the stone moves through the urinary tract. Nausea, blood in the urine, and an urgent need to urinate are common. The pain often starts suddenly and is hard to get comfortable with, no matter what position you try. Diagnosis usually involves a CT scan or ultrasound to confirm the stone and measure its size.
Kidney Infection
A kidney infection on the left side produces a deeper, more constant ache in the left flank, often with fever, chills, and painful urination. Unlike kidney stones, which cause cramping waves of pain, a kidney infection tends to be a steady throb that worsens when the area is pressed. Urinalysis and blood work help distinguish between the two.
Left Rib Cage and Chest Wall
Costochondritis
Costochondritis is inflammation of the cartilage connecting your ribs to your breastbone, and it happens most often on the left side. The pain is sharp or pressure-like and can radiate to your arms and shoulders, which is why many people initially fear a heart problem. The key distinguishing feature is that the pain worsens with deep breaths, coughing, sneezing, or any twisting of your chest wall. Pressing on the rib joints reproduces the tenderness. It often affects more than one rib at a time and typically resolves on its own over weeks, though anti-inflammatory pain relievers can help.
Pleurisy
The lining around your lungs can become inflamed from infection, autoimmune disease, or other causes. Left-sided pleurisy produces a stabbing chest pain that sharpens with each breath. It differs from costochondritis in that the pain is deeper and tied to breathing rhythm rather than to pressing on the rib joints. Pneumonia on the left side can produce similar pain along with fever and cough.
Reproductive Causes in Women
The left ovary and fallopian tube sit in the lower-left pelvis, and several gynecological conditions cause pain in that area.
A ruptured ovarian cyst produces sudden, sharp pain in the lower belly or back, sometimes with vaginal spotting and abdominal bloating. Most ruptured cysts resolve without treatment, but severe nausea and vomiting can signal ovarian torsion, where the weight of the cyst causes the ovary to twist and cut off its own blood supply. That’s a surgical emergency.
An ectopic pregnancy, where a fertilized egg implants in the left fallopian tube instead of the uterus, causes worsening left-sided pelvic pain as the pregnancy grows. Faintness, dizziness, or heavy vaginal bleeding alongside the pain are signs of a potentially life-threatening rupture that requires immediate emergency care.
When Left-Side Pain Is an Emergency
Most left-sided pain has a benign explanation, but certain patterns demand immediate attention. Go to an emergency room rather than urgent care if you experience any of the following:
- Severe pain that makes it difficult to move, eat, or drink
- Sudden onset of intense pain with no clear trigger
- High fever alongside abdominal pain
- Blood in your stool or vomit
- Abdominal pain after trauma, such as a fall, car accident, or blow to the torso
- Faintness, dizziness, or rapid heartbeat with the pain
One important note: heart attacks can present as pain or pressure in the upper abdomen under the rib cage, sometimes with severe nausea, rather than classic chest-clutching pain. This is especially true in women and older adults. If there’s any doubt about whether your left-sided pain could be cardiac, the safest choice is the emergency room.