The flu responds to two categories of medicine: prescription antivirals that fight the virus itself, and over-the-counter products that manage symptoms like fever, body aches, and cough. Antivirals work best when started within 48 hours of your first symptoms, so timing matters. For most healthy adults with a mild case, OTC symptom relief is all that’s needed, but antivirals can shorten the illness and prevent serious complications in people at higher risk.
Prescription Antivirals
Antivirals are the only medicines that actually target the influenza virus rather than just masking symptoms. The two most commonly prescribed options are oseltamivir (originally sold as Tamiflu, now widely available as a generic) and baloxavir (Xofluza). Oseltamivir is taken as a pill twice a day for five days. Baloxavir is a single-dose pill, which makes it convenient, and studies in children show it resolves symptoms slightly faster, averaging about 74 hours compared to roughly 83 hours with oseltamivir. Baloxavir also clears fever faster, by about 5 hours on average.
There are also inhaled and IV antivirals available in specific clinical situations, but oseltamivir and baloxavir are what most people will encounter. Your doctor doesn’t need to wait for a test result to prescribe one. If your symptoms and the timing fit, treatment can start right away, and in fact it should: every hour counts during that early window.
The 48-Hour Window
Antivirals deliver the most benefit when you start them within 48 hours of feeling sick. Multiple large analyses of clinical trials confirm that early treatment with antivirals shortens both fever and overall symptom duration in otherwise healthy adults and children. After 48 hours, the benefit drops, though it doesn’t disappear entirely. One trial in children found that starting oseltamivir as late as 72 hours into the illness still cut symptoms by about a day compared to no treatment.
For people sick enough to be hospitalized, antivirals can still help even when started four or five days after symptoms begin. The takeaway: if you’re in a high-risk group or feeling very ill, it’s worth calling your doctor even if you’ve passed the two-day mark. But for the best results, don’t wait.
Who Should Get Antivirals
Not everyone with the flu needs a prescription antiviral. Doctors typically prioritize them for people at higher risk of complications: adults 65 and older, children under 2, pregnant women, and people with chronic conditions like asthma, diabetes, or heart disease. Pregnant women in any trimester are advised to start antiviral treatment as soon as flu is suspected, without waiting for test results. Oseltamivir is the preferred choice during pregnancy.
If you’re a healthy adult with a straightforward case of the flu, your doctor may or may not prescribe an antiviral depending on how early you’re seen and how severe your symptoms are. It’s worth asking, especially if you’re within that first 48-hour window.
Over-the-Counter Fever and Pain Relief
Acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) are the go-to options for flu-related fever, headaches, and body aches. Both work well. The maximum daily dose for adults is 3,000 mg of acetaminophen or 2,400 mg of ibuprofen. Ibuprofen also reduces inflammation, which can help with sore throat and muscle pain, while acetaminophen is gentler on the stomach.
One critical safety point for parents: never give aspirin to children or teenagers with the flu. Aspirin use during influenza is linked to Reye’s syndrome, a rare but potentially fatal condition that causes swelling in the liver and brain. Stick to acetaminophen or ibuprofen for kids, and always dose by weight as directed on the label.
If you’re taking a multi-symptom cold and flu product, check the ingredients carefully. Many of these combination medicines already contain acetaminophen. Taking a separate dose of Tylenol on top of one can push you past the safe daily limit without realizing it.
Cough, Congestion, and Sore Throat
Multi-symptom flu products typically combine a pain reliever with some mix of a cough suppressant, a decongestant, and an antihistamine. The most common cough suppressant in OTC flu medicines is dextromethorphan, which temporarily calms the cough reflex. It won’t cure anything, but it can help you sleep. Guaifenesin, often paired with dextromethorphan, is an expectorant that loosens mucus so you can cough it up more easily.
For nasal congestion, pseudoephedrine (sold behind the pharmacy counter) is more effective than phenylephrine, which was recently found by the FDA to be no better than a placebo when taken orally. Antihistamines like doxylamine or diphenhydramine can help with a runny nose and sneezing, though they cause drowsiness, which can be a benefit or a drawback depending on the time of day.
Throat lozenges, warm liquids, and honey (for anyone over age 1) are simple measures that genuinely help with sore throat and cough. These aren’t just folk remedies; honey in particular has performed comparably to some OTC cough suppressants in studies.
Zinc and Elderberry
Zinc lozenges have the strongest evidence of any supplement for respiratory infections. A meta-analysis of trials using zinc acetate lozenges (80 to 92 mg per day) found they shortened the duration of nasal congestion, sore throat, cough, and muscle aches. The catch is timing: zinc needs to be started within 24 hours of symptoms to show benefit. After that, the effect fades.
Elderberry extract has shown more modest results. A meta-analysis of four studies found that black elderberry supplements reduced both the duration and severity of upper respiratory symptoms compared to placebo. The studies were small, however, and the evidence isn’t strong enough to consider elderberry a reliable treatment. It’s reasonable to try, but it’s not a substitute for antivirals if you’re in a high-risk group.
Side Effects to Watch For
Oseltamivir’s most common side effects are nausea and vomiting, which can be reduced by taking it with food. In children and teenagers, there have been reports of unusual behavioral and neurological reactions, including confusion, hallucinations, and delirium. These reports are rare, but parents should be aware of them. If your child starts acting unusually after taking an antiviral, contact your doctor.
OTC decongestants containing pseudoephedrine can raise blood pressure and cause insomnia or jitteriness. Antihistamines cause drowsiness and dry mouth. None of these are dangerous for most people at recommended doses, but they add up when you’re layering multiple products. The simplest approach is often the best: pick the one or two symptoms bothering you most and treat those specifically, rather than reaching for a product that tries to cover everything at once.