Unexplained symptoms are worth exploring, but it's important to first speak to your GP and have potential medical causes appropriately investigated. This library is for information only and does not replace medical advice, diagnosis or testing.
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Nausea describes the unpleasant sensation of feeling sick or as though you might vomit, although vomiting does not always occur.
It can feel like a queasy stomach, an unsettled sensation in the abdomen, a rising wave of sickness or a general feeling of being physically unwell.
For some people, nausea is clearly associated with eating, travelling or an illness. For others, it appears without an obvious reason, sometimes when the stomach is empty or when no digestive symptoms are present.
Nausea can occur on its own or alongside other sensations, including:
Dizziness or lightheadedness.
Sweating, warmth or chills.
Increased saliva or a dry mouth.
Stomach discomfort or bloating.
Loss of appetite.
A racing heart or feeling faint.
Headaches or sensitivity to movement.
Nausea can occur in many conditions, including gastrointestinal disorders, migraine, vestibular conditions, dysautonomia, ME/CFS, Long COVID and other chronic illnesses.
It may be mild and fleeting, persistent throughout the day or experienced in sudden, intense waves.
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Nausea involves communication between the digestive system, nervous system and brain.
Although nausea is often felt in the stomach, the sensation is not necessarily caused by a problem within the stomach itself.
Several systems can contribute to the experience, including digestion, balance, circulation, hormones and the brain's processing of internal bodily signals.
The Brain and Nausea
The brain contains networks that coordinate nausea and vomiting, including areas within the brainstem.
These networks receive information from different parts of the body, including the digestive tract, inner ear and bloodstream.
They also interact with brain regions involved in sensations, emotions and awareness of the body's internal state.
This helps explain why nausea can occur in many different situations, from a stomach infection to motion sickness or migraine.
Nausea and vomiting are related but distinct processes. Someone can experience intense nausea without ever vomiting.
The Gut-Brain Connection
The digestive system and brain communicate continuously through nerves, hormones and chemical messengers.
An important part of this communication involves the vagus nerve, which carries information between internal organs and the brainstem.
Signals from the stomach and intestines can contribute to nausea, particularly when digestion, stomach stretching or gastrointestinal movement changes.
However, nausea can also originate from processes outside the digestive system.
This is why someone may feel profoundly sick despite having no stomach pain, digestive upset or identifiable gastrointestinal condition.
The Autonomic Nervous System
The autonomic nervous system regulates involuntary bodily functions, including digestion, heart rate, blood pressure and sweating.
Nausea is often accompanied by autonomic responses such as sweating, changes in saliva production, paleness or a sensation of faintness.
In conditions involving autonomic dysfunction, such as postural orthostatic tachycardia syndrome (POTS), nausea may occur alongside dizziness, palpitations or difficulty remaining upright.
For some people, nausea becomes more noticeable when standing or moving around.
These experiences can involve changes in circulation and autonomic regulation rather than a problem with the stomach alone.
Balance and the Inner Ear
The vestibular system, located within the inner ear, helps the brain understand movement, balance and spatial orientation.
It works alongside information from the eyes and muscles to establish where the body is in space.
When these signals conflict or are processed differently, nausea can develop.
Motion sickness is a familiar example, but nausea can also accompany vestibular migraine, vertigo and persistent dizziness.
Some people experience nausea in response to movement, busy visual environments or changes in head position, even without feeling that the room is spinning.
Digestion and Stomach Emptying
The stomach normally moves food into the small intestine through coordinated muscular contractions.
When this process is disrupted, people may experience nausea, early fullness, bloating or discomfort after eating.
For example, gastroparesis involves delayed stomach emptying and can cause persistent nausea.
Other digestive conditions, including reflux and functional dyspepsia, can also produce nausea.
However, nausea does not necessarily indicate delayed digestion or an underlying gastrointestinal disorder.
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When the brain perceives a threat, the body activates its stress response, often described as fight or flight or survival mode.
During this response, the autonomic nervous system changes how the body functions, including heart rate, circulation and digestion.
Digestive activity can slow or change, and signals travelling between the gut and brain can contribute to sensations of nausea.
This is why people sometimes feel sick before an important event, during periods of anxiety or following a frightening experience.
For some people, prolonged stress or heightened nervous system sensitivity may contribute to recurring nausea, even when there is no obvious digestive problem.
Nausea itself can also feel threatening, potentially increasing alertness and making the sensation more noticeable.
However, survival mode is not a medical diagnosis or an explanation for every experience of nausea. Many physical conditions can produce the same symptom.
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Nausea doesn't always lead to vomiting.
Someone can experience persistent or intense nausea without ever being physically sick.
Nausea isn't always a stomach problem.
The sensation can arise from processes involving the brain, balance system, circulation, hormones or nervous system.
You can feel nauseous without stomach pain.
Some people experience a general feeling of sickness without abdominal discomfort, bloating or other digestive symptoms.
Nausea can accompany dizziness.
The systems responsible for balance and nausea are closely connected, so these sensations often occur together.
An empty stomach can sometimes feel nauseating.
Nausea may occur before eating, after eating or independently of meals.
Nausea and loss of appetite are different.
Someone may feel nauseous but hungry, or experience a reduced appetite without feeling sick.
The sensation can come in waves.
Nausea may rise and fall suddenly, sometimes disappearing completely between episodes.
Nausea can be difficult to locate.
Although often associated with the stomach, some people describe feeling sick in their throat, chest, head or throughout their whole body.
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Nausea can be particularly difficult to describe because it doesn't always feel like the familiar sensation of being about to vomit.
The unsettled stomach: Experiencing a persistent queasy or uncomfortable feeling in the abdomen.
The rising wave: Feeling a sudden rush of sickness that builds, peaks and gradually subsides.
The throat sensation: Experiencing nausea as an uncomfortable feeling in the throat or upper chest rather than the stomach.
The whole-body sickness: Feeling generally unwell or sick without being able to identify a particular location.
The motion-related nausea: Becoming nauseous when walking, turning the head, travelling or looking at moving images.
The nausea with dizziness: Experiencing sickness alongside lightheadedness, imbalance or a sensation of faintness.
The morning nausea: Waking with a queasy feeling before eating or beginning the day's activities.
The unpredictable episode: Feeling completely comfortable before nausea suddenly develops without an obvious explanation.
The lingering nausea: Experiencing a low-level feeling of sickness that remains present for hours or throughout the day.
For some people, nausea is closely connected to meals, movement or other recognisable situations. For others, it can appear seemingly at random.
The sensation itself may also change. One episode might feel like a queasy stomach, while another involves dizziness, sweating or a general sense of being unwell.
This unpredictability can make nausea particularly disruptive, especially when someone cannot anticipate when it will appear or how long it will last.
Nausea may also overlap with fatigue, headaches, digestive discomfort, dizziness and other chronic symptoms, making it difficult to separate one experience from another.
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Nausea can occur for many reasons, including infections, digestive conditions, migraine, medication effects, hormonal changes and disorders affecting the nervous system.
New, persistent, recurrent or unexplained nausea may warrant medical assessment, particularly when it affects eating, drinking or everyday functioning.
Nausea accompanied by unexplained weight loss, persistent vomiting, significant abdominal pain or other new symptoms should be discussed with a healthcare professional.
Severe abdominal pain, vomiting blood, signs of severe dehydration or nausea accompanied by sudden serious neurological symptoms can require urgent medical attention.
