Left-sided stomach pain has many possible causes, ranging from trapped gas to conditions that need prompt medical attention. What’s causing yours depends largely on where exactly the pain is, how it feels, and what other symptoms come with it. The left side of your abdomen contains your stomach, spleen, pancreas, left kidney, part of your colon, and (in women) the left ovary, so pain in this area can originate from several different organs.
Upper Left Pain: Stomach, Spleen, and Pancreas
If your pain is above or near your belly button on the left side, the most likely culprits are your stomach, pancreas, or spleen. Gastritis and stomach ulcers cause a burning or gnawing ache that often worsens after eating or on an empty stomach. This type of pain tends to be fairly localized and may come with nausea or a feeling of fullness.
Pancreatitis produces upper belly pain that radiates to your back or shoulders and typically gets worse after meals. Chronic pancreatitis causes constant upper abdominal pain, while the acute form comes on suddenly and can be severe. Heavy alcohol use and gallstones are the two most common triggers.
Spleen problems are less common but more urgent. A splenic infarction (blocked blood flow to the spleen) causes sudden, severe pain in the upper left abdomen that can spread to your left shoulder. If you also feel dizzy, lightheaded, or nauseated alongside worsening upper left pain, that’s an emergency room situation, as it may signal internal bleeding.
Trapped Gas at the Splenic Flexure
One of the most common and least serious causes of upper left abdominal pain is gas trapped at a sharp bend in your colon called the splenic flexure, located just under your left ribcage. This can produce surprisingly sharp pain along with bloating, fullness, and sometimes nausea. Because the pain can feel intense and sudden, it’s easily mistaken for something more serious. The key difference is that splenic flexure pain tends to improve when you pass gas or have a bowel movement, and it doesn’t come with fever or other warning signs. Diagnosing it can take time because providers need to rule out other conditions with similar symptoms first.
Lower Left Pain: Diverticulitis
Diverticulitis is one of the most common causes of lower left abdominal pain, especially in adults over 50. It happens when small pouches in the colon wall become inflamed or infected. The hallmark is steady, aching pain in the lower left side of your belly, often accompanied by fever, nausea, and changes in bowel habits.
While diverticulitis has traditionally been considered an older person’s condition, the trend is shifting. A UCLA analysis of 5.2 million hospitalizations for diverticulitis between 2005 and 2020 found that about 16% of cases occurred in patients younger than 50. Even more concerning, the proportion of younger patients with complicated diverticulitis (involving abscesses or perforations) rose from 18.5% to 28.2% over that period. So if you’re under 50 with persistent lower left pain, don’t assume age rules this out.
Doctors diagnose diverticulitis through a combination of physical exam, blood tests looking for signs of infection, and imaging. A CT scan is the gold standard for confirming the diagnosis and spotting complications. Ultrasound is also effective, with a sensitivity of about 92.5% for detecting acute diverticulitis, though it’s less reliable at catching complicated cases.
Kidney Stones on the Left Side
A kidney stone lodged in or moving through your left ureter can cause pain that starts in your lower back or side and radiates toward your groin. This pain is distinctive: it comes in waves, intensifying and then easing before ramping up again. It can range from a dull ache to sharp, severe pain that makes it hard to sit still. You may also notice blood in your urine, pain when urinating, or an urgent need to urinate frequently. Kidney stone pain doesn’t improve with position changes or bowel movements, which helps distinguish it from intestinal causes.
Ovarian Cysts and Reproductive Causes
For women, left-sided lower abdominal pain can originate from the left ovary or fallopian tube. Ovarian cysts are fluid-filled sacs that often form during ovulation and usually resolve on their own. When they cause symptoms, you may feel a dull ache or sharp pain below your belly button toward one side, along with bloating, fullness, or pressure in your abdomen. The pain can come and go.
Two ovarian complications require immediate attention. Ovarian torsion, where the ovary twists on itself, causes sudden and severe pelvic pain with nausea and vomiting. A ruptured cyst can also trigger intense pain and internal bleeding. Both are emergencies. An ectopic pregnancy, where a fertilized egg implants in the fallopian tube instead of the uterus, is another serious cause of one-sided lower abdominal pain in women of reproductive age.
Muscle Strain and Abdominal Wall Pain
Sometimes the problem isn’t an organ at all. Muscle strains, pulled abdominal muscles, or even shingles (a reactivation of the chickenpox virus along a nerve) can mimic internal organ pain and are often misdiagnosed. One way doctors test for this is called Carnett’s sign: they press on the painful spot while you lift your head and shoulders off the exam table, tensing your abdominal muscles. If the pain increases when you tense up, it’s more likely coming from the abdominal wall rather than an internal organ. If it decreases, the source is probably deeper.
Muscle-related pain tends to be worsened by movement, twisting, or coughing and may be tender to the touch in a specific spot. It often follows a clear trigger like exercise, heavy lifting, or a recent illness with lots of coughing.
Warning Signs That Need Urgent Care
Most left-sided abdominal pain resolves on its own or has a manageable cause. But certain symptoms alongside the pain signal something more serious:
- Vomiting blood or seeing blood in your stool or urine
- Fever or chills along with abdominal pain
- Severe pain that comes on suddenly or keeps getting worse
- Not being able to pass gas or have a bowel movement, which may indicate a bowel obstruction
- Yellowing of your skin or eyes
- Shortness of breath with abdominal pain
Mild pain that gradually worsens over days or weeks, or pain that keeps returning in the same spot, also warrants a visit to your provider even if it doesn’t feel like an emergency. Many of the conditions that cause left-sided pain are straightforward to diagnose with a physical exam and basic imaging, and getting an answer early makes treatment simpler.