What exactly is nausea?

Nausea is that unpleasant, hard-to-describe sensation between your throat and stomach that warns you "vomiting may be coming." But here's the catch: feeling nauseous doesn't mean you'll actually throw up. They're two different things.

Vomiting is a reflex motor act (your body just does it). Nausea, on the other hand, is a conscious experience your brain builds. That's why, paradoxically, nausea is often harder to treat than the actual vomiting. ¹

From an evolutionary standpoint, nausea is an alarm system: your body detected something "off" (a toxin, a virus, an unusual movement, big worry) and turns on the red light. The trouble starts when the alarm stays on without a clear reason.

How nausea is built (the 4 pathways)

There's no single "nausea center." It's a network of neurons in the medulla oblongata that receives input via four different routes. Understanding this helps you understand why the same symptom can come from such different origins. ²

That's why patients with functional dyspepsia or irritable bowel syndrome can have persistent nausea even when all tests come back clean: the network is hypersensitized. ³

Most common causes of constant nausea

1) Digestive causes (the ones I see most)

These are the protagonists in my clinic. They include gastroparesis (stomach empties too slowly, common in diabetics), gastroesophageal reflux, ulcers, functional dyspepsia, Helicobacter pylori infection, hepatitis, pancreatitis, cholecystitis and bowel obstructions. ⁴

If nausea comes with chronic abdominal pain or early satiety (you feel full after just a few bites), the digestive suspicion is high and an endoscopy is usually warranted.

2) Medications and toxins

Antibiotics, anti-inflammatories, opioids, antidepressants, oral iron, anticonvulsants, chemotherapy, alcohol… If your nausea started right after beginning a new medication, you've got a big clue. It's one of the first things I always check. ⁵

3) Pregnancy

Up to 80% of pregnant women experience nausea, especially in the first trimester. The severe form (hyperemesis gravidarum) affects 1–3% and needs medical treatment. It's the most common metabolic-hormonal cause of nausea in young women. ⁶

4) Central nervous system

Migraine (a vastly underestimated cause), increased intracranial pressure (tumors, hydrocephalus), stroke, meningitis. A key clue: morning nausea with intense headache or projectile vomiting demands ruling out neurological causes.

5) Vestibular causes

Motion sickness, positional vertigo, labyrinthitis, Ménière's disease. If your nausea comes with a spinning sensation or imbalance, the source is usually the inner ear.

6) Metabolic and endocrine

Decompensated diabetes (ketoacidosis), kidney failure with uremia, hypothyroidism, hypercalcemia, adrenal insufficiency. Here, nausea usually comes with fatigue, abnormal lab tests and other systemic symptoms.

7) Psychogenic and anxiety-related

Anxiety and depression activate the gut-brain axis and can produce real, persistent nausea. It's not "faking it": there's neurological evidence shown by neuroimaging. ⁷

Functional nausea: when everything looks "normal"

Here's the most important part of this post: there's a group of patients who get an endoscopy, ultrasound, full blood work… and everything comes back fine. And they still have nausea every single day. This is called functional nausea and it's not "made up": it's a recognized disorder under the international Rome IV criteria. ⁸

What's happening is that the gut-brain axis is hypersensitized. There are alterations in gastric motility, in the autonomic nervous system (more sympathetic, less parasympathetic), increased duodenal mast cells, and even visible changes in brain regions like the insula and anterior cingulate cortex when functional MRI is done during a nausea episode. ⁹

Red flags: when to see a doctor without delay

Treatment: what actually works

Here's the part everyone wants to hear about. And the answer I always give in clinic: there is no single magic antiemetic. The choice depends on the cause, intensity and your profile. Let me break it down by blocks. ¹⁰

A) First: basic measures that actually work

• Small, frequent meals (every 2–3 hours).
• Avoid fats, spicy food and strong smells that trigger your symptoms.
• Constant hydration, in small sips.
• Rest with your head elevated after eating (30–45 min).
• Ginger: 1 g/day has moderate evidence, especially in pregnancy.

B) Antiemetics by cause

C) Chronic functional nausea: neuromodulators

When classic antiemetics don't work (typical in functional nausea), another strategy comes in: recalibrating the gut-brain axis with low doses of tricyclic antidepressants (amitriptyline, nortriptyline), mirtazapine, gabapentin or olanzapine. ¹¹

We don't use them for their antidepressant effect, but because they modulate visceral sensitivity and the nausea network at doses far below psychiatric ones. They work, and they work well.

D) Non-pharmacological treatments with evidence

• Acupuncture/electroacupuncture at P6 point: solid evidence in post-chemo and post-operative nausea.
• Inhaled isopropyl alcohol aromatherapy: relieves acute nausea faster than ondansetron in some studies.
• Cognitive behavioral therapy: very useful in functional nausea with anxiety component.
• Clinical hypnosis and guided relaxation: emerging evidence.
• Moderate physical exercise: regulates the gut-brain axis.

E) When gastroparesis is the cause

If the cause is refractory gastroparesis (paralyzed stomach), a technique I practice in my daily work that's changing the field is G-POEM (endoscopic pyloromyotomy). It's done endoscopically, with no scars, and improves symptoms in around 70–80% of selected patients.

Related reading (to understand the "full map")

Gut-brain axis

How your gut and brain talk to each other and why it matters.

Read post →

Gastroparesis & G-POEM

When your stomach empties too slowly.

Read post →

Persistent belching

Updated clinical guide on belching disorders.

Read post →

FAQ: quick questions about constant nausea