The most common causes include:

• Food poisoning – This can happen if you eat food that has gone bad. It is basically an infection in your stomach. Infections like these often also cause diarrhea. Other kinds of infections that affect the stomach or intestines can also cause nausea and vomiting.
• Dizziness or motion sickness – This can happen if you’re on a boat or in a car, or something else that moves. It can also happen if there’s something wrong inside your ears that affects your balance.
• Medicines – Lots of different medicines can cause nausea or vomiting. Some examples are antidepressants, antibiotics, vitamins, birth control pills, and pain medicines. People who are on chemotherapy for cancer treatment or who have been under anesthesia also often have nausea or vomiting. Sometimes, people who use cannabis (marijuana) over a long time have repeated episodes of vomiting.
• Pregnancy – Many women who are pregnant have nausea or vomiting. People sometimes call this “morning sickness,” but it can happen at any time of day.
  Gastroesophageal reflux disease (GERD) – GERD is a condition that causes the juices that are in the stomach to leak back up into the esophagus, the tube that connects the throat to the stomach. It can sometimes cause nausea.
• Problems with the stomach or intestines – In some people, the stomach or intestines do not move food along the way that they are supposed to. In others, the intestines can get blocked. Both of these problems can cause nausea or vomiting.
• Migraine headaches – Some people who get migraine headaches have nausea during their headaches.
• Alcohol – Drinking too much alcohol can cause nausea and vomiting.