Pain on your left side can come from dozens of different structures, and where exactly you feel it narrows the list considerably. Your left abdomen houses your stomach, spleen, pancreas, left kidney, and parts of your colon, while the lower left contains the sigmoid colon and, in women, the left ovary and fallopian tube. Muscles, ribs, and even your heart can also send pain to the left side of your body. Here’s how to sort through the most common causes.
Upper Left Side Pain
Pain above or around your belly button on the left typically involves the stomach, pancreas, spleen, left kidney, or the bend in your colon that sits just below the spleen. The most common culprits are stomach-related: gastritis (inflammation of the stomach lining) and peptic ulcers both produce a burning or gnawing ache in the upper left that often gets worse after eating or on an empty stomach. Acid reflux can cause similar discomfort, sometimes radiating up toward the chest.
Kidney stones lodged on the left side tend to cause intense, wave-like pain that starts in the flank (the area between your ribs and hip on your back) and radiates forward or downward. A kidney infection produces a steadier, deep ache in the same area, usually with fever and painful urination. Pancreatitis, inflammation of the pancreas, causes a boring pain in the upper abdomen that often wraps around to the back and typically worsens after eating fatty foods. Lipase levels more than three times the normal range on a blood test are a strong indicator.
An enlarged or injured spleen is a less common but important cause. The spleen sits just under your left rib cage and can swell from infections like mononucleosis or from blood disorders, producing a dull fullness or sharp pain in that area.
Lower Left Side Pain
The single most common cause of acute lower left abdominal pain in adults is diverticulitis, an infection or inflammation of small pouches that form in the colon wall. Diverticulosis (having the pouches) affects 5 to 10 percent of people by age 45 and up to 80 percent by age 80. Most people with diverticulosis never have symptoms, but 10 to 20 percent eventually develop diverticulitis. The classic presentation is left-sided lower belly pain combined with fever. About 25 percent of people who get diverticulitis will have it again.
Other gastrointestinal causes of lower left pain include constipation (which often causes crampy, pressure-like discomfort that eases after a bowel movement), inflammatory bowel disease like Crohn’s or ulcerative colitis, and infectious colitis from a bacterial or viral gut infection. A hernia in the left groin can also trap tissue and cause sudden, localized pain.
Kidney stones passing through the left ureter frequently cause pain that radiates from the back down into the lower abdomen and groin. A urinary tract infection can produce a similar but duller ache along with burning during urination and frequent trips to the bathroom.
Causes Specific to Women
In women, the left ovary and fallopian tube sit in the lower left pelvis and can produce pain from several conditions. Ovarian cysts, fluid-filled sacs on the ovary, often cause a dull ache or sudden sharp pain if they rupture. Endometriosis, where tissue similar to the uterine lining grows outside the uterus, can cause chronic pelvic pain that worsens around menstruation. Ovulation itself sometimes causes a brief, one-sided twinge known as mittelschmerz. An ectopic pregnancy, where a fertilized egg implants in the left fallopian tube instead of the uterus, produces sharp, escalating pain and is a medical emergency.
In men, prostatitis or inflammation of the seminal vesicles can refer pain to the lower left abdomen, though it’s more commonly felt in the groin or perineum.
Rib and Muscle Pain
Not all left-sided pain comes from inside the abdomen. Musculoskeletal causes are extremely common and can convincingly mimic organ problems. Intercostal muscle strain, a pulled muscle between the ribs, produces a sharp, localized pulling sensation that worsens with movement, deep breathing, coughing, or sneezing. You might also notice stiffness, tightness, or muscle spasms at the site.
Costochondritis, inflammation of the cartilage connecting your ribs to your breastbone, triggers chest wall pain that can feel alarming but is harmless. It typically hurts more when you press on the area or twist your torso. Pleurisy, inflammation of the membrane surrounding the lungs, causes a sharp pain with each breath and often follows a viral illness, especially one that involved heavy coughing.
A useful clue: if the pain changes noticeably when you shift position, take a deep breath, or press on the spot, a musculoskeletal cause is more likely than an internal organ problem.
When Left-Sided Pain Involves the Heart
Left-sided chest pain that extends into the upper abdomen, jaw, back, neck, arm, or shoulder can signal a heart attack. This pain is typically a pressure, squeezing, or heaviness rather than a sharp stab, and it may come with shortness of breath, nausea, or sweating. Aortic dissection, a tear in the wall of the body’s largest artery, causes sudden, severe ripping pain in the chest or back. An aortic aneurysm, a bulging weak spot in the aorta, can also produce deep chest or abdominal pain if it begins to leak or rupture. All three are life-threatening emergencies.
How Left-Sided Pain Gets Diagnosed
Doctors start with where the pain is, what it feels like, and when it started. They’ll press on your abdomen to check for tenderness or masses. From there, the workup depends on the suspected cause.
Blood tests typically include a complete blood count to check for infection or anemia, a C-reactive protein level to gauge inflammation, and a urinalysis to look for urinary tract infection or kidney stones. For women of childbearing age, a pregnancy test is standard. If pancreatitis is a concern, lipase levels are checked.
For imaging, a CT scan with contrast is the go-to choice for both upper left and lower left abdominal pain when the diagnosis isn’t clear. It provides detailed views of the pancreas, spleen, kidneys, intestines, and blood vessels. Ultrasound can identify uncomplicated diverticulitis, kidney stones, and free fluid in the abdomen. For straightforward-sounding diverticulitis in an otherwise healthy person, doctors may sometimes make the diagnosis based on symptoms alone and reserve imaging for cases where they’re less certain. A colonoscopy may follow later to confirm diverticular disease and rule out other conditions like cancer.
Signs That Need Immediate Attention
Severe pain that comes on suddenly should raise concern for a vascular emergency like a ruptured aneurysm, a perforated ulcer, or torsion of an ovary. Pain that wakes you from sleep is considered serious until proven otherwise. Vomiting blood or material that looks like coffee grounds points to bleeding in the stomach or esophagus. Bloody stool combined with significant abdominal pain suggests the intestinal lining may be losing its blood supply.
A sudden urge to have a bowel movement during acute abdominal pain has been described as a warning sign of serious conditions, including ruptured aneurysm in older adults and ruptured ectopic pregnancy in younger women. Any combination of abdominal pain with low blood pressure, rapid heart rate, fever, or a generally “ill” appearance warrants emergency evaluation. Older adults face higher risks from acute abdominal conditions overall, making prompt assessment especially important in that group.