Constipation can cause nausea because: A full colon can put pressure on your small intestine and stomach, making you feel sick. Constipation can cause “bad” gut bacteria to build up, making you feel queasy. Your colon is blocked with stool, so food and liquids can’t move out of your stomach. Food sitting in your stomach for too long can lead to acid reflux (GERD). This stomach acid backup can cause nausea. Mild cases of constipation may respond to exercise, diet changes or drinking more water. But severe constipation may require medical care. The team at DispatchHealth cares for people with constipation and other digestive issues every day. We come to you, so you can receive expert medical care in the comfort of home.