Most cases of stomach flu (viral gastroenteritis) clear up on their own within one to three days, and no medication will kill the virus causing it. What you can do is treat each symptom individually with the right over-the-counter products while keeping yourself hydrated. Here’s what actually helps, what to avoid, and when the situation calls for something stronger.
For Diarrhea: Loperamide and Bismuth Subsalicylate
Two over-the-counter options can slow diarrhea down, though neither addresses the underlying infection. Loperamide (sold as Imodium) works by slowing the movement of your intestines, giving your body more time to absorb water from stool. It’s effective at reducing the number of trips to the bathroom, but it can cause drowsiness and nausea as side effects.
Bismuth subsalicylate (Pepto-Bismol, Kaopectate) takes a gentler approach with fewer side effects. Adults can take it as chewable tablets or liquid, up to 16 tablets or 16 tablespoons of regular-strength liquid in a 24-hour period. It helps with both diarrhea and nausea, making it a reasonable first choice for stomach flu specifically.
There’s an important warning for both products: do not take them if you notice blood in your stool or have a high fever. Those symptoms can signal a bacterial infection like dysentery rather than a viral illness, and slowing your gut down in that situation can trap the bacteria inside and make things worse.
For Nausea and Vomiting
Over-the-counter phosphorated carbohydrate solutions (sold under the brand name Emetrol) can help settle nausea. You take it by mouth without diluting it, and you shouldn’t drink any other fluids for at least 15 minutes after a dose. You can repeat the dose every 15 minutes until the nausea eases, but don’t exceed five doses in one hour. If five doses don’t help, the nausea is likely too severe for this product to manage on its own.
Bismuth subsalicylate also has mild anti-nausea effects, so if you’re dealing with both diarrhea and nausea, it can pull double duty.
When vomiting is severe enough that you can’t keep fluids down, a prescription anti-nausea medication called ondansetron (Zofran) is the standard option doctors turn to. It’s widely used for both children and adults with gastroenteritis, specifically because it helps people tolerate oral rehydration. If you’re vomiting everything you drink for more than several hours, this is worth calling your doctor about rather than waiting it out.
For Fever and Body Aches
Acetaminophen (Tylenol) is the safer choice for pain and fever during stomach flu. Ibuprofen (Advil, Motrin) and similar anti-inflammatory painkillers can irritate an already inflamed stomach lining, potentially making nausea and discomfort worse. Stick with acetaminophen unless you have a specific reason not to.
What Not to Give Children
Bismuth subsalicylate contains a compound closely related to aspirin. Giving aspirin or aspirin-containing products to children under 16 who have a viral illness raises the risk of Reye’s syndrome, a rare but serious condition that causes liver failure and brain damage. It’s fatal in up to 2 out of 5 cases. Many over-the-counter products contain aspirin-related ingredients without making it obvious on the front label, so read the full ingredient list carefully before giving anything to a child.
Loperamide is also not recommended for young children. For kids with stomach flu, the priority is fluid replacement with an oral rehydration solution (like Pedialyte) rather than medication to stop symptoms. If a child is vomiting too frequently to keep fluids down, ondansetron can be prescribed by their pediatrician to break the cycle.
Probiotics Can Shorten the Illness
One supplement with real evidence behind it is the probiotic strain Lactobacillus rhamnosus GG. Multiple analyses of clinical trials have found that it shortens the duration of acute diarrhea by roughly one day. For rotavirus infections specifically, the reduction was closer to two days. You can find this strain in certain yogurts and in capsule or powder form at most pharmacies. It’s not a dramatic fix, but shaving a full day off a miserable illness is meaningful.
Hydration Matters More Than Any Medication
The biggest risk from stomach flu isn’t the virus itself. It’s dehydration from losing fluids through vomiting and diarrhea faster than you can replace them. Oral rehydration solutions containing water, salt, and sugar are absorbed more efficiently than plain water. For adults, sports drinks or diluted juice with a pinch of salt work in a pinch, though commercial rehydration products like Pedialyte or Drip Drop are better formulated.
Take small, frequent sips rather than gulping large amounts, especially if you’re still nauseous. Ice chips can help when even sips feel like too much. Signs that dehydration is becoming dangerous include very dark urine, dizziness when standing, a dry mouth that persists even after drinking, and in children, no tears when crying or no wet diapers for several hours. People who can’t keep any fluids down despite trying anti-nausea medication, or who show signs of severe dehydration, typically need IV fluids in a medical setting.
Antibiotics Don’t Work for Stomach Flu
Stomach flu is caused by viruses, most commonly norovirus or rotavirus. Antibiotics only kill bacteria, so they’re useless here and can actually worsen diarrhea by disrupting your gut’s normal bacterial balance. The exception is if your doctor determines you have a bacterial infection (from contaminated food, for instance) rather than a viral one, which is a different diagnosis entirely.