Have you not heard of people having stomach cramps or even diarrhea after drinking MCT oil? That's the best evidence to show that MCT oil does not cause constipation. But if you're taking MCT oil powder, then you might feel constipated. Why?
To make MCT oil powder, you need fillers. And most fillers in MCT oil powder are dietary fiber. As you know, dietary fiber may gather and clog up your intestines if you do not drink enough water. They can also block the glycerols (from the breaking down of MCT) from reaching your stools.
Glycerols from MCT can help make your stool soft and easy to slip out.
That said, when you take MCT oil powder, you need to drink more water to make sure the fillers in the powder do not cause constipation.
Keep in mind that if you've always had constipation issues, try to avoid MCT oil powder. Choose pure MCT oil instead.