Pain in the lower left side of your stomach usually comes from structures in that area: the end of the large intestine (sigmoid colon), the left ureter, or in women, the left ovary. The most common causes range from something as simple as trapped gas or constipation to conditions like diverticulitis, which is the single most likely diagnosis when lower left abdominal pain is persistent and accompanied by fever. What’s actually going on depends on how the pain feels, how suddenly it started, and what other symptoms you have.
Trapped Gas and Constipation
The simplest and most common explanation is gas or backed-up stool. Your large intestine makes a sharp bend on the left side of your abdomen, near the spleen. Gas can get trapped at this bend, a pattern sometimes called splenic-flexure syndrome, and produce pain sharp enough to be confused with something more serious. Constipation concentrates stool in the sigmoid colon, which sits in the lower left quadrant, causing cramping, bloating, and pressure that can feel surprisingly intense.
Gas pain typically comes and goes in waves, shifts location, and improves after passing gas or having a bowel movement. If the pain resolves within a few hours and you have no fever, blood in your stool, or vomiting, this is the most likely explanation.
Diverticulitis
Diverticulitis is the condition most closely associated with lower left abdominal pain. Small pouches called diverticula form in the wall of the colon over time, especially after age 50, and are extremely common. When one or more of these pouches becomes inflamed or infected, the result is sudden, often intense pain in the lower left abdomen. In some cases the pain starts mild and worsens over a day or two, or it fluctuates in intensity.
Other signs include fever, nausea, tenderness when the area is pressed, and changes in bowel habits like sudden diarrhea or constipation. If uncomplicated (meaning no abscess, perforation, or blockage), current clinical guidelines recommend managing diverticulitis without antibiotics in people who are otherwise healthy and not running a high fever. Antibiotics are reserved for people who are visibly unwell, immunocompromised, or have complicated disease. Most uncomplicated cases resolve with rest, a temporary liquid diet, and pain management at home.
A CT scan is the gold standard for confirming diverticulitis, with 100% sensitivity and specificity in studies. Ultrasound can also be used as a first-line tool, catching about 94% of cases, though it’s less reliable for ruling out the condition entirely.
Irritable Bowel Syndrome
If your lower left pain keeps coming back over months and tends to be linked to bowel movements, IBS is a strong possibility. It’s diagnosed when you’ve had recurrent abdominal pain at least one day per week for the past three months, with symptoms first appearing at least six months earlier. The pain needs to be connected to at least two of the following: it improves or worsens with bowel movements, it coincides with changes in how often you go, or it coincides with changes in the appearance of your stool.
IBS pain is often crampy, comes with bloating, and alternates between constipation and diarrhea. It does not cause fever, bloody stool, or unintentional weight loss. If you’re experiencing any of those, something else is going on.
Ulcerative Colitis
Left-sided ulcerative colitis causes inflammation that extends from the rectum up through the lower portion of the colon. The hallmark symptoms are bloody diarrhea, abdominal cramps concentrated on the left side, and a frustrating urge to have a bowel movement even when you can’t pass anything (called tenesmus). This is a chronic condition that tends to flare and remit over time.
Unlike IBS, ulcerative colitis produces visible blood in the stool and can be detected through stool tests that look for white blood cells and specific inflammatory proteins. If you’re seeing blood consistently, this warrants investigation.
Kidney Stones
A stone moving through the left ureter, the tube connecting your kidney to your bladder, can cause severe pain in the lower left abdomen. This pain has a distinctive quality: it comes in intense waves (colic), often radiates into the groin, and doesn’t improve in any position. You may feel like you can’t sit still.
As a stone moves lower toward the bladder, the pain pattern shifts. Stones near the bladder tend to cause urinary urgency, frequent urination, burning with urination, and pain that radiates into the inner thigh or, in men, the scrotum. If your lower left pain came on suddenly, is severe and wave-like, and you’re also having urinary symptoms, a kidney stone is a likely culprit.
Causes Specific to Women
In women, the left ovary and fallopian tube sit in the lower left quadrant. An ovarian cyst on the left side can cause a dull ache or sharp pain, particularly if it ruptures or twists. Endometriomas, a type of cyst caused by endometriosis, can grow on the left ovary and produce chronic pelvic pain that worsens during periods. These are typically diagnosed through pelvic ultrasound, and surgical removal is generally recommended when they’re painful, growing, or larger than about 4 centimeters.
An ectopic pregnancy, where a fertilized egg implants outside the uterus (often in a fallopian tube), can cause sudden, sharp lower abdominal pain on one side. This is a medical emergency. If there’s any chance you could be pregnant and you’re experiencing sudden one-sided lower abdominal pain, especially with vaginal bleeding or dizziness, seek immediate care.
Inguinal Hernia
An inguinal hernia occurs when tissue pushes through a weak spot in the lower abdominal wall, near the groin. It’s far more common in men and often produces a visible or palpable bulge along with discomfort, heaviness, or a burning sensation. The pain typically gets worse when you strain, lift, cough, or stand for long periods, and improves when you lie down.
Most inguinal hernias aren’t emergencies, but a hernia that suddenly becomes larger, very painful, or can no longer be pushed back in may be strangulated, meaning its blood supply is cut off. Strangulation can cause fever, nausea, vomiting, and severe tenderness, and requires emergency treatment.
When the Pain Needs Urgent Attention
Most lower left abdominal pain turns out to be something manageable. But certain features signal a potentially serious problem that needs same-day or emergency evaluation:
- Sudden, severe pain that came on abruptly, especially if it’s the worst abdominal pain you’ve ever felt
- Fever alongside abdominal tenderness
- Blood in your stool or vomit, or dark, tarry stools
- Pain that worsens with any movement or jarring, like hitting a bump in the car or someone bumping into you (this suggests peritonitis, inflammation of the abdominal lining)
- Inability to pass gas or stool combined with vomiting and bloating, which can indicate a bowel obstruction
- Dizziness, rapid heartbeat, or fainting, which may signal internal bleeding
A person who is completely still and experiences increased pain when the bed is moved or when they’re touched is showing classic signs of peritoneal irritation, which requires urgent surgical evaluation. If your pain is mild, came on gradually, and isn’t accompanied by any of these warning signs, it’s reasonable to monitor it for a day or two before seeking care.