13 Surprising Causes of Constipation

What causes constipation? Well, the obvious culprits include a low fiber diet, repeatedly ignoring the urge to go, not drinking enough water, or a lack of exercise.

But constipation also has other, less-well-known causes, including certain medications and supplements, as well as potentially serious medical conditions.

What’s causing your gut trouble? Here are 13 possible causes of constipation you may not have considered.

1. Hypothyroidism

Hypothyroidism, or an underactive thyroid gland, slows the body’s metabolic processes—even the gut.

Not everyone with an underactive thyroid has constipation, nor do all cases of constipation mean that the butterfly-shaped gland in your neck is underperforming.

Still, "when I see a young person who’s constipated more than normal and really complaining, I do tend to get a thyroid level," says Carla H. Ginsburg, MD, assistant professor of medicine at Harvard Medical School in Boston.

2. Painkillers

Painkillers, specifically narcotics, can cause constipation.

"A lot of receptors for the narcotic class of drugs are in the digestive tract, so it tends to bring everything to a halt," says Thomas Park, MD, a gastroenterologist with the University of Rochester Medical Center Park in New York. "In general, it’s a good idea for everyone who’s placed on one of these drugs to also place them on a gentle laxative like a stool softener."

Some studies (but not all) have suggested that there might be a higher risk of constipation for people who are chronic users of pain relievers like aspirin and ibuprofen.