Some common causes of nausea are gastroenteritis and other gastrointestinal disorders, food poisoning, motion sickness, dizziness, migraine, fainting, low blood sugar, anxiety, hyperthermia, dehydration and lack of sleep.

[8] Some of the most frequently associated include cytotoxic chemotherapy regimens for cancer and other diseases, and general anaesthetic agents.

An old cure for migraine, ergotamine, is well known to cause devastating nausea in some patients; a person using it for the first time will be prescribed an antiemetic for relief if needed.

[citation needed] Nausea or "morning sickness" is common during early pregnancy but may occasionally continue into the second and third trimesters.

These include pancreatitis, small bowel obstruction, appendicitis, cholecystitis, hepatitis, Addisonian crisis, diabetic ketoacidosis, increased intracranial pressure, spontaneous intracranial hypotension, brain tumors, meningitis, heart attack, rabies,[14] carbon monoxide poisoning and many others.

There are four general pathways that are activated by specific triggers in the human body that go on to create the sensation of nausea and vomiting.

Autonomic effects involve increased salivation and the sensation of feeling faint that often occurs with nausea and vomiting.

Symptoms that occur within an hour of eating may indicate an obstruction proximal to the small intestine, such as gastroparesis or pyloric stenosis.

An infectious cause of nausea and vomiting such as gastroenteritis may present several hours to days after the food was ingested.

Emesis of undigested food points to an obstruction prior to the gastric outlet, such as achalasia or Zenker's diverticulum.

[15] When a history and physical exam are not enough to determine the cause of nausea and vomiting, certain diagnostic tests may prove useful.

More advanced imaging and procedures may be necessary, such as a CT scan, upper endoscopy, colonoscopy, barium enema, or MRI.

[15] If dehydration is present due to loss of fluids from severe vomiting, rehydration with oral electrolyte solutions is preferred.

[22] Nausea and vomiting associated with migraine headaches respond best to dopamine antagonists such as metoclopramide, prochlorperazine, and chlorpromazine.

[22] In cases of gastroenteritis, serotonin antagonists such as ondansetron were found to suppress nausea and vomiting, as well as reduce the need for IV fluid resuscitation.

[23] Other factors to consider when choosing an antiemetic medication include the person's preference, side-effect profile, and cost.

[24][25] Several studies have demonstrated the therapeutic effects of cannabinoids for nausea and vomiting in the advanced stages of illnesses such as cancer and AIDS.

Repeated intentional vomiting, characteristic of bulimia, can cause stomach acid to wear away at the enamel present on the teeth.