Food Poisoning in London 2026. How Long It Lasts, the Dehydration Signs That Matter and When a Visitor Needs a Doctor
Most food poisoning settles on its own within a week, and the treatment that matters most is replacing the fluid you are losing. NHS guidance is clear on this. The reason to speak to a doctor is not the diarrhoea or vomiting itself but the signs that you are becoming dehydrated, that the illness is lasting longer than it should, or that something other than a simple stomach bug is going on.
Key points
Symptoms usually start within hours to a few days of eating the food responsible, and usually improve within a week.
Fluids come first. Small, frequent sips, and oral rehydration solution if you are losing a lot, prevent most of the problems food poisoning causes.
Blood in your diarrhoea, diarrhoea for more than 7 days, vomiting for more than 2 days, or signs of dehydration that persist despite rehydration all need medical advice.
Antibiotics are not needed for most food poisoning, and anti-diarrhoea tablets should be avoided if you have a fever or blood in your stool.
Unwell in your hotel? Message a GMC-registered doctor on WhatsApp or email team@thewellnesslondon.com.
What are the symptoms of food poisoning?
The usual symptoms are feeling sick, vomiting, diarrhoea, tummy cramps, a high temperature and feeling generally unwell. They typically begin within a few hours or a few days of eating the food that caused it, although some infections take longer to appear, which is why the last meal is not always the culprit.
Norovirus, the winter vomiting bug, causes very similar symptoms and spreads easily between people and on surfaces, so an illness that starts in several people who did not share a meal is more likely to be a virus than the food.
How long does food poisoning last?
Most people start to improve within a day or two and are better within a week. Vomiting usually settles first. Diarrhoea can take a little longer, and a few days of reduced appetite and tiredness afterwards is normal.
An illness that is not improving after a few days, or that is getting worse rather than better, deserves a conversation with a doctor rather than more waiting.
How to rehydrate properly
Take small sips often rather than large drinks, which tend to come straight back up. Water is fine for most adults. If you are losing a lot of fluid, or are older or have other health conditions, oral rehydration sachets from any pharmacy replace the salts and sugar that water alone does not.
Pale yellow urine is the simplest sign you are keeping up. Dark, strong-smelling urine or passing much less than usual means you need more fluid. Eat when you feel able to, starting with plain food. Alcohol and very sugary drinks make diarrhoea worse.
Travelling adds its own problems. Long flights, heat, disrupted sleep and not drinking enough while sightseeing all make dehydration more likely, and many visitors underestimate how quickly it builds.
When should you see a doctor?
NHS guidance advises urgent advice if signs of dehydration persist after using oral rehydration solution, if there is blood in your diarrhoea or bleeding from the bottom, if diarrhoea lasts more than 7 days, or if vomiting lasts more than 2 days.
Seek help the same day if you are pregnant, are older, have diabetes, kidney disease or a weakened immune system, or take medicines that can be affected by dehydration, such as diuretics, some blood pressure tablets and metformin. Some of these need to be paused while you are unwell, and a doctor can advise which.
Call 999 or go to A&E if you vomit blood or material that looks like coffee grounds, have severe tummy pain, feel faint or confused, or cannot keep any fluid down.
Worried it is more than a stomach bug? Ask a doctor on WhatsApp.
Do you need antibiotics?
Usually not. Most food poisoning is caused by viruses or by bacteria that clear on their own, and antibiotics do not help the first and are rarely needed for the second. A doctor will consider them in specific situations, for example severe illness with fever, blood in the stool, a weakened immune system or recent travel to certain regions, and may arrange a stool test first to identify the cause.
Anti-diarrhoea tablets can be useful to get through a journey or a meeting, but they should be avoided if you have a high temperature or blood in your stool, because they can keep the infection in the gut for longer.
How to avoid passing it on
Wash your hands with soap and water after using the toilet and before handling food, since alcohol gel does not reliably kill norovirus. Avoid preparing food for others, and stay off work until you have been free of vomiting and diarrhoea for 48 hours.
How same-day care works at The Online GP
For visitors to London, and for residents who cannot wait for an NHS appointment, a GMC-registered doctor speaks with you by telephone or video the same day. The doctor assesses how dehydrated you are, reviews your regular medicines, advises what to pause, and prescribes where treatment will genuinely help, with the prescription sent to a pharmacy near your hotel or home. Where examination or tests are needed, you are seen in person at Portman Square, and where anything suggests a more serious illness, you are directed to hospital care without delay.
Where we are
Portman Square, Marylebone
The Wellness is at Unit 4, 10 Portman Square, London W1H 6AZ, a short walk from Marble Arch and Baker Street.
Belgravia
Appointments also run at the Light Centre, 9 Eccleston Street, London SW1W 9LX, close to Victoria.
What it costs
At The Online GP the consultation price includes the doctor's assessment, advice on your regular medicines, a prescription where appropriate and a clear plan if things change.
Telephone consultation with a GMC-registered doctor, 15 minutes, the same day, £59.
Same-day urgent appointment in person at Portman Square, 30 minutes, with examination, £220.
Stool tests, blood tests and a fit-to-fly letter arranged where they are needed.
See a doctor today. Message us on WhatsApp.
Why visitors choose The Online GP by The Wellness
Because you do not need an NHS registration, a local address or a long wait to speak to a doctor.
Because a doctor checks your regular medicines, which is where dehydration causes the most avoidable harm.
Because antibiotics are given when they help and not when they do not, which is what gets you better and back to your trip fastest.
And because the same team can see you in person, arrange tests and provide travel paperwork if your flight home is approaching.
Related reading
Our guides to a hotel doctor in London, forgotten or lost medication and the private GP in London explain how visitors get care quickly.
Book a same-day consultation. Message us on WhatsApp, email team@thewellnesslondon.com, or call +44 20 3951 3429.
Frequently asked questions about food poisoning
How long does food poisoning last?
Most people improve within a day or two and recover within a week. Vomiting usually settles first, and diarrhoea can take a little longer.
When should I see a doctor for food poisoning?
If you still have signs of dehydration after using oral rehydration solution, have blood in your diarrhoea, have diarrhoea for more than 7 days or vomiting for more than 2 days, or are pregnant, older or have a long-term condition.
Do I need antibiotics for food poisoning?
Usually not. Most cases clear on their own. A doctor may consider antibiotics for severe illness, fever with blood in the stool or a weakened immune system, often after a stool test.
How can I tell food poisoning from norovirus?
The symptoms are very similar. Illness that spreads between people who did not share a meal is more likely to be norovirus. Treatment is the same, with fluids first.
Can I see a doctor in London as a tourist?
Yes. A private GP can assess you by telephone or video the same day, with no NHS registration, and send any prescription to a pharmacy near your hotel.
This article is for information and does not replace personal medical advice. If you vomit blood, have severe tummy pain, feel faint or confused or cannot keep fluids down, call 999 or go to A&E. Written and reviewed by the clinical team at The Wellness. Last updated September 2026.