Pain on the left side of your stomach can mean many different things depending on exactly where you feel it. The most common causes range from gas and muscle strain to conditions like diverticulitis, kidney stones, or gastritis. Where the pain sits, whether it’s upper or lower, sharp or dull, and what other symptoms come with it all help narrow down what’s going on.
Upper Left Stomach Pain
Pain in the upper left part of your abdomen, roughly behind and below your left ribs, typically involves the stomach itself, the pancreas, the spleen, or the left kidney. The most frequent culprits are gastritis (inflammation of the stomach lining) and peptic ulcers, which tend to cause a burning or gnawing sensation that may worsen after eating or on an empty stomach. Acid reflux can produce a similar feeling higher up, closer to your chest.
Pancreatitis is a more serious possibility. It often starts as mild upper abdominal pain that gets worse when you eat, then escalates into severe, constant pain. Nausea, fever, and a rapid pulse often come along with it. This is especially worth considering if you drink alcohol heavily or have gallstones.
The spleen sits in the upper left abdomen and can cause pain if it becomes enlarged from infection, liver disease, or blood disorders. A left kidney stone can also radiate pain into this area, though it more commonly starts in the back or flank before wrapping around toward the front.
Less commonly, upper left abdominal pain can be cardiac in origin. Heart attacks and angina sometimes present as upper abdominal discomfort rather than classic chest pain, particularly in women and older adults. If the pain comes with shortness of breath, sweating, or jaw or arm pain, treat it as a heart-related emergency.
Lower Left Stomach Pain
Pain in the lower left abdomen is most often related to the colon, specifically to small pouches called diverticula that form in the bowel wall. These pouches are extremely common: roughly 5 to 10 percent of people over 45 have them, and that number climbs to about 80 percent by age 85. Most of the time they cause no symptoms at all. But when one becomes inflamed or infected, the result is diverticulitis, and it almost always strikes the lower left side.
Diverticulitis typically causes constant pain in the lower left abdomen, often accompanied by a low-grade fever (usually under 102°F), changes in bowel habits, and sometimes nausea. The pain tends to develop over hours to days rather than appearing suddenly. While it’s more common in older adults, rates have been rising sharply in younger people. One analysis found that hospital admissions for diverticulitis in people aged 18 to 44 increased by 82 percent over a seven-year period. Interestingly, people under 50 who get diverticulitis actually have a slightly higher chance of it coming back (about 16 percent) compared to those over 50 (about 12 percent).
Other lower left causes include constipation, irritable bowel syndrome, and inguinal hernias. Trapped gas in the left side of the colon, near the bend called the splenic flexure, is one of the most benign explanations and can produce surprisingly sharp pain that resolves on its own.
Kidney Stones and Urinary Causes
A stone forming in or passing through the left kidney produces pain that can land anywhere from your lower back to your side to your lower abdomen, sometimes radiating down toward the groin. The hallmark of kidney stone pain is that it comes in waves. You might feel fine for a few minutes, then get hit with an intense cramp that builds, peaks, and fades. This wave-like pattern, called renal colic, is fairly distinctive. The pain can be dull or sharp and severe, and it often shifts location as the stone moves through the urinary tract.
A urinary tract infection or kidney infection on the left side can also cause left-sided abdominal or flank pain, usually with fever, burning during urination, or cloudy urine.
Causes Specific to Women
In women, the left ovary and fallopian tube sit in the lower left pelvis, adding several possible explanations. An ovarian cyst on the left side can cause a dull ache or sudden sharp pain if it ruptures. Endometriosis, where tissue similar to the uterine lining grows outside the uterus, frequently causes chronic pelvic pain that may be worse on one side.
An ectopic pregnancy, where a fertilized egg implants in a fallopian tube instead of the uterus, is a serious emergency that causes sharp, one-sided lower abdominal pain. It can be accompanied by vaginal bleeding and dizziness. If you’re of reproductive age and experiencing sudden, severe left-sided lower pain, an ectopic pregnancy needs to be ruled out quickly.
Pelvic inflammatory disease, usually caused by sexually transmitted infections, and uterine fibroids are additional possibilities that can produce left-sided pelvic discomfort.
Causes Outside the Organs
Not all left-sided stomach pain comes from an internal organ. The abdominal wall itself can be the source. A pulled or strained muscle on the left side, common after exercise or heavy lifting, produces pain that gets worse when you tense your core, cough, or twist.
Shingles is a less obvious but important cause. Before the characteristic rash appears, the reactivated virus can cause burning or stabbing pain along a band on one side of the abdomen. In about 10 percent of cases, the pain and even visible abdominal bulging show up before any rash, which can make it confusing to diagnose initially. If the pain follows a strip-like pattern on one side and feels like burning or electric shocks on the skin surface, shingles is worth considering.
How Doctors Figure Out the Cause
Location and character of the pain narrow the list considerably, but imaging often clinches the diagnosis. For lower left abdominal pain, a CT scan with contrast is the standard first-line imaging study. It’s particularly good at identifying diverticulitis, with a diagnostic accuracy around 98 percent, and it can also pick up alternative diagnoses that mimic the same symptoms. Ultrasound is sometimes used as a less invasive first step, but it can miss up to 80 percent of complicated diverticulitis cases, so CT remains the preferred tool when the diagnosis is uncertain.
For upper left pain, CT is also useful because it can visualize the pancreas, spleen, kidneys, and blood vessels all at once. Blood work, urine tests, and sometimes a pregnancy test for women of reproductive age round out the initial workup.
Signs That Need Urgent Attention
Most left-sided stomach pain turns out to be something manageable, but certain patterns signal a problem that needs immediate care. Pain so severe it interrupts your ability to function, pain paired with vomiting so persistent you can’t keep liquids down, complete inability to have a bowel movement combined with worsening pain, or pain that resembles something you’ve had before but feels notably different or more intense all warrant an emergency visit.
A rigid abdomen that hurts when you press and then release (rebound tenderness), a high fever, rapid heartbeat, or signs of blood in your vomit or stool are additional red flags. If you’ve had prior abdominal surgery, adhesions can cause bowel obstructions that produce sudden, severe pain with bloating and vomiting.