Nausea: why it happens and what to do

Nausea is that queasy feeling in your stomach, with an urge to vomit. Sometimes it ends in vomiting and sometimes it doesn’t. It is a symptom, not a disease: what matters is finding the cause.

This page helps you narrow down the most likely cause and tells you when it is an emergency. If your child has vomiting and diarrhea, see diarrhea and vomiting in children.

According to MedlinePlus, the most frequent causes are:

• A stomach virus or food poisoning: see stomach bug
• Reflux or heartburn: see acid reflux and gastritis
• Migraine: see migraine
• Motion sickness on a boat, a cruise or in the car: see seasickness
• Medicines, such as chemotherapy or GLP-1 medicines, like semaglutide (Ozempic for type 2 diabetes, Wegovy for weight management) and tirzepatide (Mounjaro for type 2 diabetes, Zepbound for weight)
• Pregnancy (morning sickness)
• Severe pain, for example from a kidney stone
• A food allergy, or frequent marijuana use

Nausea is one of the first symptoms of pregnancy. If there is any chance, take a drugstore pregnancy test before you take medicine for nausea. If it is positive, book with an OB-GYN for prenatal care and ask them what you can take for nausea.

When it is a warning sign: according to MedlinePlus, hyperemesis gravidarum causes nausea and vomiting much stronger than normal morning sickness. Call your OB or go to the ER if you cannot keep any fluids down for 12 hours, see blood in your vomit, have belly pain, dizziness, dark urine or other signs of dehydration, or have lost more than 5 pounds.

MedlinePlus recommends drinking small amounts of clear liquids often (water, oral rehydration solution, broth) rather than a lot at once, and stopping a medicine that may be causing the nausea only after talking to your doctor.

Watch for signs of dehydration: dry mouth, more thirst, urinating less or dark yellow urine, sunken eyes or crying without tears. In Puerto Rico’s heat, vomiting can dehydrate you quickly: see dehydration.

Ondansetron (Zofran) is a prescription medicine for nausea and vomiting. According to MedlinePlus, it blocks the action of serotonin, a natural substance that triggers nausea. It is approved to prevent nausea from chemotherapy, radiation therapy and surgery, and doctors sometimes also prescribe it for nausea from other causes. Whether it is right for you depends on what is causing your nausea, your age, your heart and the other medicines you take.

Heart caution: according to the FDA-approved label (DailyMed), ondansetron can prolong the QT interval, a change in the heart’s rhythm seen on an electrocardiogram. The label says to avoid it in people with congenital long QT syndrome and to monitor more closely people with low potassium or magnesium, heart failure, a slow heart rate, or who take other medicines that prolong the QT. That is why the doctor asks about your heart and your medicines before deciding. According to MedlinePlus, get help right away if you have chest pain, shortness of breath, dizziness or light-headedness, fainting, or a fast, slow or irregular heartbeat while taking it.

Nausea in pregnancy: according to MedlinePlus, ondansetron is sometimes prescribed for nausea during pregnancy, but that is your doctor’s decision based on your situation; do not take leftover ondansetron or someone else’s. Read more about pregnancy symptoms.

Over the counter: for motion sickness, according to the CDC, there are over-the-counter pills such as dimenhydrinate and meclizine, which work best taken before you travel; see how to prevent seasickness. For other causes, which medicine is safe depends on the cause, your age, your heart and whether you could be pregnant, so read the label and ask first, especially for a child.

In an online doctor visit, available 24/7, the doctor looks for the cause and, if appropriate, prescribes ondansetron or another medicine and we send your prescription to your pharmacy. If you vomit blood, have severe belly pain or signs of dehydration, such as no urine in 8 hours, do not wait for a prescription: see when to go to the ER.

According to MedlinePlus, nausea, vomiting and diarrhea are common side effects of semaglutide (Wegovy, approved for weight management, and Ozempic, approved for type 2 diabetes) and tirzepatide (Zepbound for weight, Mounjaro for type 2 diabetes). That is why the dose usually starts low and goes up step by step. If the nausea is severe or does not go away, tell the doctor at your weight-loss visit. Get medical care right away if you have belly pain that will not go away and may spread to your back, with or without vomiting.

You see Dr. Diana Nieves Castro, a Puerto Rico-licensed general practice physician with several years of emergency-department experience, in English or Spanish. She asks when the nausea started, whether you are vomiting and how often, whether you have pain, fever or diarrhea, what you ate, whether you traveled, which medicines you take and whether you could be pregnant.

We evaluate, diagnose and treat. If appropriate, the doctor prescribes a medicine for the nausea or its cause, and we send your prescription to your pharmacy. If needed, we give you a lab order for a lab near you: for example a blood count, electrolytes, liver and kidney tests, or a urine test.

An online doctor visit has the same price for every age. If the patient is under 21, a parent or legal guardian stays on camera for the whole visit and shows ID. Video doctor visits 24/7 — book online and choose your time right away.

According to MedlinePlus, call 911 or go to the ER if you think the vomiting is from a poison or a substance, or if you see blood or dark material like coffee grounds in the vomit. Get medical care right away if:

• You have severe stomach or belly pain
• You have a bad headache or a stiff neck
• You have been vomiting for more than 24 hours, or can’t keep fluids down for 12 hours or more
• You vomited 3 or more times in a day, or haven’t urinated for 8 hours or more
• You have nausea with chest pain or pressure, or shortness of breath: it may be your heart, call 911
• You are confused or very drowsy