Cyclic vomiting syndrome (CVS) causes repeated episodes of severe nausea and vomiting that start suddenly, last hours to days, and then settle completely. Between episodes, most people feel well. The pattern tends to repeat in a similar way each time.
CVS affects adults as well as children. Because each episode can look like food poisoning or a stomach bug, many people visit the emergency department several times, sometimes over several years, before the pattern is recognised.
The four phases
- Warning phase: nausea, sweating, looking pale or a sense that an episode is coming, often lasting minutes to an hour or two
- Vomiting phase: intense, repeated vomiting, sometimes several times an hour, often with abdominal pain and exhaustion
- Recovery phase: the vomiting stops and appetite and energy gradually return
- Well phase: weeks or months without symptoms until the next episode
Features that suggest CVS
- At least three similar episodes in a year, each lasting less than a week
- Little or no vomiting between episodes
- Episodes often start in the early morning
- A personal or family history of migraine
- Recognisable triggers, such as stress or excitement, lack of sleep, infections, fasting, travel or menstrual periods
- Relief from long hot showers or baths
Getting a diagnosis
There is no single test for CVS. The diagnosis is based on the pattern of episodes, after other causes of vomiting have been ruled out. Depending on symptoms, this may include blood tests, a gastroscopy, and a scan of the abdomen to look for a blockage. Occasionally other tests are needed, such as a scan of the brain or tests for hormonal or metabolic conditions.
Regular cannabis use can cause a very similar pattern, called cannabinoid hyperemesis syndrome, so your doctor will ask about it. A diary of episodes, with dates, length and possible triggers, is very useful at the first consultation.
Treatment
- Preventing episodes: for frequent or severe episodes, a daily low-dose amitriptyline is usually used to prevent them. It typically takes several weeks to work, and the dose is adjusted gradually. Other medicines are available if amitriptyline is not suitable.
- Stopping an episode early: taking anti-sickness medicine, and sometimes a migraine medicine, during the warning phase can shorten or stop an episode. Resting in a quiet, dark room also helps.
- During a severe episode: hospital treatment with intravenous fluids, anti-sickness medicine and sedation may be needed.
- Daily habits: regular sleep, regular meals, managing stress and avoiding known triggers. Anxiety and low mood are common with CVS and are worth treating too.
An agreed written plan, which you can show at an emergency department, helps you get the right treatment quickly during an episode.
General information only. Reviewed by Dr Chia Chung King, 2026-11-07. Book a consultation.