Nausea and Vomiting

Nausea is the unpleasant feeling that you may vomit. Vomiting is the forceful expulsion of stomach or upper intestinal contents. Either symptom can arise from the gut, balance system, medicines, pregnancy, migraine, metabolic illness or another condition.

Nausea and vomiting are related but different Nausea is the unpleasant feeling that you may vomit. It can occur without vomiting, and vomiting can sometimes occur with little warning nausea. Vomiting is the forceful expulsion of contents from the stomach and sometimes the upper small intestine. Retching uses similar muscle movements without bringing material up. Regurgitation is different. It is the more passive return of food or fluid into the mouth, without the forceful abdominal contractions of vomiting. These distinctions provide useful clues, but people may find them difficult to describe during an illness. The complete pattern remains more important than one word. A brainstem network coordinates vomiting Vomiting is not controlled by one sharply defined vomiting centre. A distributed brainstem network receives several types of input and coordinates the motor sequence. Signals from the stomach and intestines can travel through nerves, including the vagus nerve. Infection, stretching, inflammation and some chemicals can activate these pathways. The balance system in the inner ear can contribute to motion sickness and vestibular disorders. This explains why vertigo and nausea often occur together. The area postrema is a brainstem structure that can detect some circulating medicines, toxins and chemical changes. It works with nearby brainstem areas rather than acting as a complete centre alone. Higher brain pathways can also contribute during migraine, strong smells, pain, anxiety or learned associations. Brain and meningeal disease can cause vomiting through several mechanisms. These inputs overlap and interact. They are not four sealed routes, and the symptom does not reveal which pathway is active. Vomiting is a coordinated physical event Vomiting involves coordinated changes in the stomach, food pipe, diaphragm, abdominal muscles and breathing. The body also attempts to protect the airway during the event. Airway protection is not guaranteed. Aspiration means vomit enters the airway or lungs, and the risk increases when alertness or swallowing is impaired. Repeated forceful vomiting can also irritate or tear the food pipe. Fluid loss, electrolyte disturbance and the underlying illness may become more important than the vomiting itself. Timing and associated symptoms matter Clinicians ask when symptoms began, how often vomiting occurs and whether fluids stay down. They also ask about diarrhoea, abdominal pain, bloating, stool and urine changes. Vomiting after meals provides context but does not reliably locate a problem. Undigested food may occur with delayed stomach emptying, obstruction, regurgitation or other conditions. Vomiting with diarrhoea and contact with an affected person can support gastroenteritis. Severe localised pain, abdominal swelling or inability to pass stool or wind raises different concerns. Headache, neck stiffness, light sensitivity, confusion, weakness, severe imbalance or drowsiness can point away from an uncomplicated stomach illness. Chest discomfort, breathlessness, faintness or sweating can indicate a heart or circulation problem. Nausea should not be assumed to come from the digestive system. Clinicians also ask about medicines, alcohol, recent surgery, travel, possible poisoning, pregnancy, diabetes and previous episodes. Several causes can occur together. The appearance of vomit can change urgency Haematemesis means blood in vomit. It may appear bright red, brown, black or like coffee granules and needs urgent medical help. Green vomit in an adult, or yellow green or green vomit in a child, needs emergency assessment. Bilious vomit can occur with bowel obstruction or another urgent condition. Yellow fluid after repeated vomiting is not always the same as clearly green bilious vomit. Colour descriptions can be difficult, so urgent advice is appropriate when uncertain. The appearance alone does not identify the bleeding site or cause. Swallowed blood, for example from a nosebleed, can also appear in vomit. Dehydration and electrolyte loss are important risks Dehydration occurs when fluid loss exceeds fluid intake. Vomiting causes fluid loss and can prevent someone from keeping enough drink down. Electrolytes are minerals such as sodium and potassium that support normal cell, nerve and muscle function. Repeated vomiting can disturb their balance. Warning signs include dark urine, reduced urination, dry mouth, dizziness, unusual tiredness and increasing drowsiness. Fast breathing or a fast heartbeat can indicate more serious dehydration. Babies, children, older adults and people who depend on others for drinks can become dehydrated more quickly. Pregnancy, diabetes and kidney disease can add further risk. Small, frequent sips may be easier to keep down. A pharmacist can advise on an oral rehydration solution when appropriate. Continue breastfeeding or usual strength formula for a baby unless a healthcare professional advises otherwise. Do not dilute formula to replace fluid. Common causes overlap with important causes Gastroenteritis and food poisoning commonly cause vomiting, often with diarrhoea. Medicines, alcohol, pregnancy, migraine, motion sickness and vestibular illness are also common contributors. Hyperemesis gravidarum is severe nausea and vomiting in pregnancy. It can cause dehydration and weight loss and needs early assessment by a midwife, doctor or maternity service. Bowel obstruction can cause vomiting with abdominal pain, swelling and reduced passage of stool or wind. Green vomit is an important warning feature. Diabetic ketoacidosis is a life threatening metabolic emergency. Vomiting with thirst, frequent urination, abdominal pain, drowsiness or deep rapid breathing needs immediate assessment. Other important causes include appendicitis, pancreatitis, severe infection, poisoning, head injury and conditions affecting the brain or its coverings. The cause cannot be ranked safely from vomiting alone. Age, context, associated symptoms and the person's overall condition guide the next step. Examination and tests answer different questions A clinician checks alertness, temperature, pulse, blood pressure, breathing and hydration. They examine the abdomen and perform a neurological assessment when the pattern requires it. A blood glucose test can detect high or low glucose. Ketone testing may be needed when diabetic ketoacidosis is possible. Blood tests may assess electrolytes, kidney function, inflammation, liver patterns or pancreatic enzymes. No result identifies the cause of vomiting alone. A pregnancy test may be important when pregnancy is possible. It detects a pregnancy hormone but does not locate the pregnancy or explain every symptom. Urine, stool or infection tests are selected from the clinical pattern. They are not routinely needed for every short episode of vomiting. Ultrasound, CT or brain imaging is used when what the person describes and the examination raise a specific question. Imaging is not automatic for uncomplicated vomiting. What may happen after assessment A short episode without warning features can often be managed with fluids, rest and clear follow up advice. Vomiting from gastroenteritis usually settles within one or two days. A clinician may prescribe anti sickness medicine when appropriate. The choice depends on the likely cause, age, pregnancy, other medicines and health conditions. Persistent vomiting, dehydration or an important associated symptom may require intravenous fluids, observation, imaging or treatment of the underlying cause. When to get help Call 999 or go to A&E for green vomit in an adult, or yellow green or green vomit in a child. Do the same after possible poisoning. Call 999 or go to A&E for vomiting with a sudden severe headache, stiff neck, marked light sensitivity or sudden severe abdominal pain. Do not drive yourself. Call 999 for blue, grey, pale or blotchy skin, severe breathing difficulty, confusion, reduced responsiveness or difficulty waking. Call 999 or go to A&E if vomiting occurs with thirst, frequent urination, rapid deep breathing, abdominal pain, drowsiness or confusion. These can be features of diabetic ketoacidosis. Vomiting blood always needs medical help. Call 999 or go to A&E if it occurs with feeling unwell, faintness, confusion, rapid breathing, clammy skin, abdominal pain or black stool. If the blood has stopped and there are no other symptoms, seek an urgent GP appointment or contact NHS 111. Contact NHS 111 if you cannot keep fluid down, have signs of dehydration or have vomited for more than two days. Seek advice sooner for a baby or young child. Contact NHS 111 after vomiting following a recent head injury. Call 999 if the person cannot stay awake, has a seizure, develops weakness or has problems speaking or walking. If you are pregnant and vomiting frequently or cannot keep food or drink down, contact your midwife, doctor or maternity service promptly. This lesson explains how nausea and vomiting are assessed. It cannot diagnose an individual episode or replace urgent medical care.

Nausea and vomiting are symptoms produced by interacting body and brain pathways, not proof of a stomach problem. The associated pattern and the person's condition determine urgency and investigation.