Constipation alternating with diarrhea is a classic symptom of irritable bowel syndrome, but also can be caused by colon cancer.

What if you find that lately, you’re experiencing this troubling symptom?

“Alternating constipation with diarrhea with abdominal pain is very classic of IBS,” says Pankaj Vashi, MD, Lead National Medical Director, National Director, Gastroenterology/Nutrition/Metabolic Support, Cancer Centers Treatment of America, whom I consulted with for this article.

Dr. Vashi continues, “When it occurs in anyone above the age of 40 with normal bowel habits prior to that, should be evaluated for other conditions like colon cancer.

“Again, in colon cancer these symptoms will be more acute and associated with other concerning symptoms.”

“Acute” means a sudden, notable onset as opposed to a gradual, quieter onset. However, the “other concerning symptoms” that can be caused by colon cancer can also be caused by IBS.

They include stomach/abdominal discomfort or pain, a feeling of having to void but nothing comes out, fatigue, unexplained weight loss and bloating.

However, a symptom that can be caused by colon cancer, but is never caused by irritable bowel syndrome, is blood in the stools.

This can appear as fresh, red blood, or as a dark or black “tarry” substance in the BMs. Ever see melted tar? This is what “tarry stools” means.

This doesn’t always mean colon cancer (other possible causes of blood in the stools are ulcers and hemorrhoids), but it DOES mean this: Don’t waste another moment in getting evaluated by a gastroenterologist.

IBS is a diagnosis of exclusion. All other causes of diarrhea alternating with constipation, including colon cancer, should be ruled out before a diagnosis of IBS is made!

For 20 years Dr. Vashi was instrumental in developing robust gastroenterology, and nutrition and metabolic support programs in all five Cancer Treatment Centers of America centers.