Hangover or Food Poisoning? How a Doctor Tells Them Apart

If you are vomiting after a night out in Vietnam, timing and temperature give the clearest answer. A hangover is present on waking: your belly stays soft, you have no fever, and you steadily improve through the day. Food poisoning starts some hours after a meal, brings a fever, causes a tender, cramping belly, and triggers watery diarrhea several times a day. Others who shared the food are often sick too. Methanol from tainted alcohol is a third possibility and requires immediate hospital emergency care.

What our doctor asks first

When a guest calls, our doctor first asks when the sickness started. Did you wake up like this, or did it begin a few hours after a meal?

Then the doctor asks what you ate, where you ate, and what you drank. Spirits from an unlabelled bottle or very cheap cocktails raise immediate suspicion.

The doctor checks how many times you vomited, whether you can keep water down, and if there is fever, diarrhea, or blood. If someone who shared the food is sick too, food poisoning is likely. Finally, the doctor asks about your regular medicines, allergies, and possible pregnancy.

What the doctor looks for on examination

Fever is the first clue. With food poisoning, the belly is tender and cramping, and there is watery diarrhea several times a day. With a hangover, the belly is soft and there is no fever.

The doctor checks dehydration: tongue, pulse, and blood pressure lying down, then standing up. The doctor also checks your eyes, breathing, and mental clarity, watching for signs of toxic alcohol.

Signs that point to a hangover

The symptoms were there when you woke up and are worst in the morning. Headache leads, with thirst, sensitivity to light and noise, and a heavy, slow feeling.

You may vomit once or twice, but you can usually keep small sips down after an hour or so. There is no fever. Loose stools can happen after drinking, but they are not the main event. By early afternoon, with water and something salty, most people are clearly better than at breakfast.

Signs that point to food poisoning

Food poisoning starts some hours after a meal rather than on waking, and it gets worse instead of better. Vomiting repeats, often with watery diarrhea and cramping belly pain. A fever, chills, or aching muscles point toward an infection like traveler's diarrhea. If someone who shared the dish is sick too, food is likely.

Dehydration is the main risk. Signs to watch for:

• Passing very little urine, or dark urine
• Dizziness when you stand up
• A dry mouth that water does not fix
• Not being able to keep anything down

Methanol: when it is not either of them

Methanol poisoning comes from bootleg spirits, sometimes served in cheap cocktails or homemade rice wine. It starts like a bad hangover, which is why it gets missed.

Methanol is treated in hospital, never with a drip at the hotel.

A drip, or just sips?

If you can keep small sips down, the doctor gives medicine for nausea and oral rehydration salts, and explains what to watch for.

A drip is needed if you cannot keep small sips down for 4 to 6 hours, or if you vomit every time you drink. The doctor also sets up an intravenous line if you are dizzy when standing, pass very little urine, or have a fast pulse.

When the answer is hospital, not the hotel

Some cases cannot be treated at the hotel. Our doctor sends you to a hospital emergency department for:

• Any sign of methanol: blurred vision, fast breathing, or confusion
• Blood in the vomit, or a lot of blood in the stool with high fever
• Strong belly pain that does not stop
• Blood pressure that stays low after fluids
• Very old patients with heart or kidney disease, pregnant women who vomit a lot, and children who are hard to wake

What to do in the next hour

Take small, frequent sips of oral rehydration solution rather than large gulps. Most pharmacies sell sachets; plain water with a little salt and sugar is a fallback. Rest somewhere cool. Skip more alcohol and skip coffee for now.

Be careful with painkillers after a heavy night. Some are hard on the liver when alcohol is still in your system, and others irritate an empty stomach. Ask a pharmacist or a doctor before taking anything. Do not take anti-diarrhea tablets if you have a fever or see blood in your stool.

If a doctor can come to you

If you cannot keep fluids down, feel faint when you stand, or are not improving by the afternoon, a doctor visit is worth it.

A licensed doctor can come to your hotel, examine you, give medicine for the nausea and, when you are dehydrated, start an IV drip in your room. Our pages on IV therapy and traveler's diarrhea explain what that involves. You can reach the team through the booking form.