Pain on Left Side of Stomach: Causes, Organs, and When to Worry

Anyone who’s ever felt a sharp twinge on the left side of their stomach knows how unsettling it can be. That location is more than just geography—it hints at which organ might be involved. In this article, we explore the common causes, the organs responsible, and the red flags that tell you it’s time to get help. One thing is clear: diverticulitis is the most common cause of lower left abdominal pain in adults over 40, according to the Cleveland Clinic.

Diverticulitis: most common cause of lower left pain in adults >40 (Cleveland Clinic) ·
Pancreatitis: pain often upper left or middle, radiates to back (Medpark Hospital) ·
Kidney stones: severe colicky pain radiating to groin (Ubie Health)

Six key facts stand out from the research, each tied to a different organ or condition.

What causes a pain in the left side of your stomach?

Diverticulitis

• Diverticulitis is the most common cause of lower left abdominal pain in adults over 40 (Cleveland Clinic).
• Steady lower left pain, fever, nausea, and bowel changes are typical (Ubie Health).

Diverticulitis is essentially inflammation of small pouches (diverticula) in the colon wall. Most diverticula form in the lower left sigmoid colon, which is why pain localizes there. The condition is common in people over 40 and often requires antibiotics or hospitalization.

Gas and indigestion

• Gas pain can be sharp but transient; often relieved by passing gas (Providence Blog).
• IBS is a common cause of left-side pain from gas during digestion (Providence Blog).

Gas collects in the splenic flexure (the sharp bend in the colon under the left ribs) and can cause sharp pains that mimic more serious conditions. The key difference: gas pain usually passes within minutes to hours and doesn’t come with fever or vomiting.

Kidney stones

• Kidney stones cause severe sharp side/back pain radiating to groin, with blood in urine (Ubie Health).

Left-sided kidney stones produce intense, colicky pain that moves from the flank around to the lower abdomen. The pain is often described as the worst pain of a person’s life and typically comes in waves.

Pancreatitis

• Pancreatitis pain is midline but can radiate left, most severe and unrelenting with nausea/vomiting (Providence Blog).

The pancreas runs across the upper abdomen, with its tail reaching toward the left side. When it becomes inflamed, the pain is often felt in the upper left or middle abdomen and radiates straight through to the back. Patients often can’t find a comfortable position.

Splenic flexure syndrome

• Gas trapped at the splenic flexure can cause left upper pain, but exact prevalence is debated.

This functional disorder occurs when gas gets stuck at the bend where the transverse colon meets the descending colon. The pain can be sharp and sudden, but it’s not dangerous. Diagnosis is usually made after ruling out other causes.

Constipation

• Constipation can cause crampy left lower pain, especially if stool is impacted in the sigmoid colon (Medpark Hospital).

Hard stool stretches the colon wall and triggers pain receptors. The discomfort is usually relieved after a bowel movement.

What organs would cause pain on your left side?

The left side of the abdomen is home to several organs. Pain location narrows the list of possibilities.

Spleen

• The spleen sits under the left rib cage; enlargement can cause pain (Cleveland Clinic).

Splenomegaly (enlarged spleen) can result from infection, liver disease, or blood disorders. Pain is typically dull and in the upper left, sometimes radiating to the left shoulder.

Pancreas

• The tail of the pancreas is on the left; pancreatitis pain often left-sided (Medpark Hospital).

Inflammation or tumors in the pancreatic tail produce left upper pain. Pancreatic cancer can present with left abdominal pain plus fatigue, weight loss, dark urine, and pale stools (Medpark Hospital).

Stomach

• Gastritis and ulcers cause left-sided pain because the stomach sits on the left (Mandaya Hospital Group).

GERD can also produce left-sided stomach pain that radiates from the epigastric region, sometimes mimicking a heart attack (Mandaya Hospital Group).

Left kidney

• The left kidney can cause flank pain with infection or stones (Cleveland Clinic).

Pyelonephritis (kidney infection) often causes deep flank pain with fever and urinary symptoms. Kidney stones produce the classic colicky pain described earlier.

Colon (descending and sigmoid)

• The descending colon and sigmoid colon are in the left lower quadrant (Cleveland Clinic).

This is where diverticulitis, colitis, and bowel obstructions occur. Inflammatory bowel disease like Crohn’s can also cause left-sided pain as the intestines occupy the abdominal cavity (Mandaya Hospital Group).

Female reproductive organs

• Ovarian cysts, ectopic pregnancy, and endometriosis can cause left lower pain (Syracuse Hernia Center).

Pain in the left lower quadrant in women may involve the left ovary or fallopian tube. Ovarian cyst rupture or torsion causes sudden, severe pain. Ectopic pregnancy can present with referred left-sided pain and vaginal bleeding.

What does pancreatitis feel like, left or right side?

The pancreas has a head on the right and a tail on the left, so pain location depends on which part is inflamed.

Symptoms of acute pancreatitis

• Severe upper abdominal pain that may radiate to the back (Medpark Hospital).
• Nausea, vomiting, fever, and elevated lipase levels.

Acute pancreatitis comes on suddenly and is often triggered by gallstones or heavy alcohol use. The pain is relentless and may worsen after eating.

Left-sided vs. right-sided pancreatitis pain

• Left-sided pain is more common in tail pancreatitis (Medpark Hospital).
• Right-sided or epigastric pain occurs in head of pancreas inflammation.

If the inflammation is concentrated in the pancreatic head (right side), pain may be felt more in the upper right or mid-epigastric area. Tail pancreatitis shifts pain to the left. Both can radiate to the back.

Acute vs. chronic pancreatitis

• Chronic pancreatitis leads to persistent left upper pain with weight loss and fatty stools.

Chronic pancreatitis develops over years, often from sustained alcohol abuse. The pain is less intense than acute but more constant, and the damaged pancreas cannot properly digest food.

How to tell if left side pain is serious?

Not all left-side pain requires a trip to the ER, but certain signs demand immediate attention.

Red flags: fever, vomiting, inability to pass gas

• Left side pain with fever may indicate diverticulitis or pancreatitis (Providence Blog).
• Inability to pass gas or stool suggests bowel obstruction (Mandaya Hospital Group).

Bowel obstruction causes lower left pain with swelling, vomiting, and an inability to pass stool or gas. It’s a surgical emergency.

When to go to emergency room

• Sudden, sharp pain that worsens is a medical emergency (Cleveland Clinic).
• Seek care for severe pain, recurrent pain, vomiting blood, blood in urine or stool, jaundice, fever, or no gas/stool (Cleveland Clinic).

Three red flags in abdominal pain

• Severe pain, high fever, vomiting blood or blood in stool (Ubie Health).

These three red flags should never be ignored. If you have even one of them, go to the emergency room immediately.

When is lower left abdominal pain in a female serious?

Women have additional causes of left lower quadrant pain related to the reproductive system.

Ovarian cysts and torsion

• Ovarian cyst rupture or torsion causes sudden, severe lower left pain (Syracuse Hernia Center).

Ovarian torsion cuts off blood flow to the ovary and requires emergency surgery. The pain is sharp, unilateral, and often accompanied by nausea and vomiting.

Ectopic pregnancy

• Ectopic pregnancy can present with referred left-sided pain and vaginal bleeding.

If a fertilized egg implants in the left fallopian tube, the pain may be on the left side. Rupture causes life-threatening internal bleeding. Any sexually active woman with sudden left lower pain should have a pregnancy test.

Endometriosis

• Chronic cyclic pain may point to endometriosis.

Endometriosis causes uterine-like tissue to grow outside the uterus, often on the left ovary or ligaments. Pain is typically worse during menstruation and may be accompanied by painful periods and infertility.

Pelvic inflammatory disease

• PID from STIs can cause left lower pain, fever, and abnormal discharge.

PID is an infection of the female reproductive organs. It can cause chronic pelvic pain and scarring if untreated.

For anyone experiencing persistent left-sided abdominal pain, the message is clear: don’t ignore red flags. If you have severe pain, fever, vomiting, or blood in your stool or urine, go to the emergency room immediately. For milder symptoms, keep a symptom diary and consult your primary care provider. For women of childbearing age, a pregnancy test and pelvic exam should be part of the workup. Acting early can turn a potential emergency into a manageable condition.

For a detailed overview of potential causes and red flags, see our guide on left side stomach pain causes.

Frequently asked questions