Nausea and Vomiting

What nausea and vomiting are

Nausea is the uneasy, queasy feeling that you might be sick. Vomiting is the forceful emptying of the stomach through the mouth. Both are controlled by a vomiting center in the brainstem, which responds to signals from the gut, the inner ear, the brain and chemicals in the blood. That is why so many different conditions, from food poisoning to migraine to pregnancy, can trigger them.

Common causes of nausea and vomiting

Infections

• Viral gastroenteritis (stomach flu): norovirus in adults and rotavirus in unvaccinated children. Sudden vomiting, then watery diarrhea, cramps and sometimes mild fever. It spreads very easily and lasts 1 to 3 days.
• Food poisoning: vomiting within 1 to 6 hours of eating suggests a toxin (for example Staphylococcus aureus or Bacillus cereus in reheated rice). Salmonella, Campylobacter and E. coli usually start 1 to 3 days after eating.
• Other infections: urinary tract and kidney infections, ear infections and strep throat in children, flu, COVID-19, hepatitis.

Pregnancy

Morning sickness affects most pregnant women, typically starting at 6 weeks, peaking at 9 weeks and easing by 14 to 16 weeks. It can happen at any time of day. Severe, persistent vomiting with weight loss is hyperemesis gravidarum and needs treatment.

Brain and inner ear

• Motion sickness from cars, boats or virtual reality
• Migraine: nausea and vomiting with a throbbing headache and sensitivity to light
• Vertigo from inner ear disorders
• Concussion and, rarely, raised pressure in the skull from bleeding or a tumor, causing morning vomiting with headache

Medicines and substances

Common culprits include chemotherapy, opioids, antibiotics, iron, metformin, GLP-1 medicines for diabetes and weight loss (semaglutide, tirzepatide), NSAIDs, digoxin and anesthesia. Alcohol, hangovers, and long-term heavy cannabis use (cannabinoid hyperemesis syndrome, often relieved by hot showers) are also common.

Digestive conditions

Other medical causes

• Diabetic ketoacidosis: vomiting, belly pain, thirst and rapid breathing in someone with diabetes
• Heart attack, especially in women, older adults and people with diabetes
• Kidney stones, kidney failure and adrenal insufficiency
• Severe pain of any kind
• Anxiety and eating disorders

Nausea and vomiting with or without diarrhea and fever

• With diarrhea: points to gastroenteritis or food poisoning.
• Without fever: common in food poisoning from toxins, pregnancy, motion sickness, migraine, medicines and hangovers.
• With fever: suggests infection, from gastroenteritis to appendicitis, kidney infection or meningitis.
• With headache: migraine is most common. Sudden severe headache, stiff neck or confusion needs emergency care.
• With belly pain that is constant and getting worse: suggests a surgical cause such as appendicitis, gallbladder disease or obstruction.

Dehydration: what to watch for

How doctors find the cause

A doctor will ask when the vomiting started, how often it happens, what the vomit looks like, about pain, diarrhea, fever, headache, possible pregnancy, food eaten, contacts who are ill, medicines, alcohol and cannabis. They will check hydration, temperature, pulse and blood pressure, and examine the belly.

Tests depend on the clues: a pregnancy test, urine test, blood tests for electrolytes, kidney and liver function, blood sugar and pancreatic enzymes, and imaging such as an ultrasound or CT scan if a surgical cause is suspected.

How to stop vomiting and recover

Rehydration first

1. Wait 30 to 60 minutes after vomiting before drinking.
2. Take small sips, about 1 to 2 teaspoons (5 to 10 ml) every few minutes, of an oral rehydration solution (ORS). Sports drinks diluted half-and-half with water are an option for adults. Avoid undiluted juice and soda, which can worsen diarrhea.
3. Gradually increase the amount as vomiting settles.
4. Breastfed babies should keep breastfeeding, in shorter, more frequent feeds.

Eating again

Once you can keep fluids down, start with small amounts of plain food such as toast, crackers, rice, bananas, potatoes or soup. There is no need to stick to a strict bland diet for long. Avoid fatty, spicy and very sweet foods and alcohol for a day or two.

Easing nausea

• Fresh air and rest, lying with the head slightly raised
• Ginger (tea, capsules or candies), which has some evidence in pregnancy and motion sickness
• Acupressure wristbands on the inner wrist point
• Eating small amounts often, rather than large meals, in pregnancy and gastroparesis

Medicines

• Motion sickness: dimenhydrinate or meclizine before travel, following the label dose. They cause drowsiness. Scopolamine patches are available on prescription.
• Prescription antiemetics such as ondansetron, metoclopramide or prochlorperazine, for severe vomiting, pregnancy sickness, migraine or chemotherapy.
• Pregnancy: vitamin B6 with or without doxylamine is a first-line treatment. Ask your doctor before taking any other medicine.
• Children: do not give anti-nausea medicines without medical advice. Never give aspirin or bismuth subsalicylate to children or teenagers.

Preventing spread

Norovirus spreads easily. Wash hands with soap and water (alcohol gel works poorly against it), clean surfaces with a bleach-based cleaner, do not prepare food for others, and stay home for 48 hours after the last vomiting or diarrhea.

Frequently asked questions

What causes nausea and vomiting?

The commonest causes are viral gastroenteritis, food poisoning, pregnancy, motion sickness, migraine, medicines and alcohol. Less common but important causes include appendicitis, gallbladder disease, pancreatitis, bowel obstruction, diabetic ketoacidosis, head injury and, rarely, heart attack.

How do I stop vomiting quickly?

Stop eating for a short time, rest, and after 30 to 60 minutes start sipping small amounts of oral rehydration solution every few minutes. Increase slowly as you tolerate it. If vomiting persists, a doctor can prescribe an anti-nausea medicine such as ondansetron.

When should I worry about vomiting?

Seek urgent care for blood or green bile in the vomit, severe belly pain, a stiff neck, confusion, vomiting after a head injury, signs of severe dehydration, or if you cannot keep fluids down for 24 hours. Young children, older adults and pregnant women should be seen sooner.

What causes nausea and vomiting without fever?

Food poisoning from toxins, pregnancy, motion sickness, migraine, medicines, hangovers, cannabis use, anxiety and gastroparesis commonly cause nausea and vomiting without fever. Some surgical problems, such as bowel obstruction, can also start without fever.

How long does a stomach bug last?

Viral gastroenteritis usually causes vomiting for about 1 day and diarrhea for 1 to 3 days. Norovirus symptoms typically last 1 to 3 days. You remain contagious for at least 48 hours after symptoms stop, so careful handwashing matters.