Most gastro (gastroenteritis / “stomach flu”) settles quite quickly, but the exact length depends on the cause and your overall health.

Typical duration

  • Viral gastro (the most common type) usually lasts about 1–3 days for the worst symptoms like vomiting and frequent diarrhoea.
  • Some viral infections can drag on longer; milder diarrhoea or tummy upset can linger for up to a week, and in some cases up to about 2 weeks.
  • Doctors often describe:
    • Acute gastroenteritis: up to 14 days
    • Persistent: 14–30 days
    • Chronic: more than 30 days, which is unusual and needs medical review.

How long you feel unwell

  • Even after vomiting and diarrhoea stop, people often feel tired, washed out, or a bit off food for several more days.
  • You can sometimes stay contagious for up to 1–2 weeks after you start to feel better, depending on the virus, so good handwashing and cleaning surfaces are important.

When it might last longer

Gastro can last longer than a few days when:

  • The cause is bacterial or parasitic rather than viral
  • You become significantly dehydrated and your recovery is slower
  • You are very young, older, pregnant, or have other medical conditions
  • There is an underlying gut issue (like IBS, inflammatory bowel disease, or coeliac disease) that gets stirred up

Some people on forums report a bad case lasting a week or more, but that’s a signal to check in with a doctor rather than just “wait it out”.

Red flags – see a doctor or emergency

Seek urgent medical care if you have any of the following:

  • Signs of dehydration: very dry mouth, hardly peeing, dark urine, dizziness, confusion
  • Blood in your stool or vomit, black/tarry stool
  • High fever, severe or worsening abdominal pain
  • Symptoms lasting more than a week without improvement, or recurring bouts
  • Gastro plus serious conditions (pregnancy, heart disease, kidney disease, weakened immune system)
  • A baby, child, older adult, or frail person with persistent vomiting/diarrhoea

If your question was about a specific case (e.g., “I’ve had gastro for X days”), sharing how long it’s been going on and your main symptoms can help tailor more precise guidance. Information gathered from public forums or data available on the internet and portrayed here.