What causes pain on left side of tummy?

Colon or ovaries: Typically the sigmoid colon or ovaries may cause pain in the lower left side of the tummy while the spleen may cause pain in the upper left portions of the abdomen. But there may be many other causes such as the small intestines or kidneys, pancreas or stomach as well.

Anything: Most people think their whole abdomen is their stomach, but the stomach is in the upper middle or upper left of the abdomen. If your lower abdomen hurts, that could be your skin, muscles, bladder, uterus, or intestines. If the upper part of your abdomen hurts, it could be acid reflux, pancreatitis, or other problems. See a doctor for an assessment.