It can be incapacitating and so severe that people refuse to continue treatment. It's important to realize that there are many effective medications for this problem. They fall into several different categories.
Many patients prefer to smoke marijuana.
These medications are much more effective when taken prophylactically. You should start taking them at least one hour before starting the chemotherapy. If you or someone you know is suffering from nausea from chemotherapy don't hesitate to ask the doctor to prescribe more medication. Cancer chemotherapy is hard enough that no one should have to endure an unnecessary amount of nausea. To get the maximum relief from nausea usually requires the use of two or three different types of drugs together.